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  • 1.
    Bin Ashraf, Faisal
    et al.
    Univ Oulu, Water Resources & Environm Engn Res Unit, POB 4300, Oulu 90014, Finland..
    Haghighi, Ali Torabi
    Univ Oulu, Water Resources & Environm Engn Res Unit, POB 4300, Oulu 90014, Finland..
    Riml, Joakim
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Alfredsen, Knut
    Norwegian Univ Sci & Technol NTNU Vassbygget, 442 Valgrinda, Trondheim, Norway..
    Koskela, Jarkko J.
    Finnish Environm Inst SYKE, Mechelininkatu 34a,POB 140, Helsinki 00260, Finland..
    Klove, Bjorn
    Univ Oulu, Water Resources & Environm Engn Res Unit, POB 4300, Oulu 90014, Finland..
    Marttila, Hannu
    Univ Oulu, Water Resources & Environm Engn Res Unit, POB 4300, Oulu 90014, Finland..
    Changes in short term river flow regulation and hydropeaking in Nordic rivers2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 17232Article in journal (Refereed)
    Abstract [en]

    Quantifying short-term changes in river flow is important in understanding the environmental impacts of hydropower generation. Energy markets can change rapidly and energy demand fluctuates at sub-daily scales, which may cause corresponding changes in regulated river flow (hydropeaking). Due to increasing use of renewable energy, in future hydropower will play a greater role as a load balancing power source. This may increase current hydropeaking levels in Nordic river systems, creating challenges in maintaining a healthy ecological status. This study examined driving forces for hydropeaking in Nordic rivers using extensive datasets from 150 sites with hourly time step river discharge data. It also investigated the influence of increased wind power production on hydropeaking. The data revealed that hydropeaking is at high levels in the Nordic rivers and have seen an increase over the last decade and especially over the past few years. These results indicate that increased building for renewable energy may increase hydropeaking in Nordic rivers.

  • 2.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Statistical Formulation of Generalized Tracer Retention in Fractured Rock2017In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 53, no 11, p. 8736-8759Article in journal (Refereed)
    Abstract [en]

    We study tracer retention in fractured rock by combing Lagrangian and time domain random walk frameworks, as well as a statistical representation of the retention process. Mass transfer is quantified by the retention time distribution that follows from a Lagrangian coupling between advective transport and mass exchange processes, applicable for advection-dominated transport. A unifying parametrization is presented for generalized diffusion using two rates denoted by k(1) and k(2) where k(1) is a forward rate and k(2) a reverse rate, plus an exponent as an additional parameter. For the Fickian diffusion model, k(1) and k(2) are related to measurable retention properties of the fracture-matrix by the method of moments, whereas for the non-Fickian case dimensional analysis is used. The derived retention time distributions are exemplified for interpreting tracer tests as well as for predictive modeling of expected tracer breakthrough. We show that non-Fickian effects can be notable when transport is upscaled based on a non-Fickian interpretation of a tracer test for which deviations from Fickianity are relatively small. The statistical representation of retention clearly shows the significance of the forward rate k(1) which depends on the active specific surface area and is the most difficult parameter to characterize in the field.

  • 3.
    Ermolaev, E.
    et al.
    Swedish University of Agricultural Sciences (SLU), Department of Energy and Technology, Box 7032, Uppsala, SE-750 07, Sweden.
    Sundberg, Cecilia
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure. Swedish University of Agricultural Sciences (SLU), Department of Energy and Technology, Box 7032, Uppsala, SE-750 07, Sweden.
    Pell, M.
    Swedish University of Agricultural Sciences (SLU), Department of Molecular Sciences, Box 7015, Uppsala, SE-750 07, Sweden.
    Smårs, S.
    Swedish University of Agricultural Sciences (SLU), Department of Energy and Technology, Box 7032, Uppsala, SE-750 07, Sweden.
    Jönsson, H.
    Swedish University of Agricultural Sciences (SLU), Department of Energy and Technology, Box 7032, Uppsala, SE-750 07, Sweden.
    Effects of moisture on emissions of methane, nitrous oxide and carbon dioxide from food and garden waste composting2019In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 240, article id 118165Article in journal (Refereed)
    Abstract [en]

    Globally, waste generation is continually increasing, with landfill as the main destination for biological waste. Composting is a simple alternative for handling waste, but when poorly managed poses a risk of greenhouse gas emissions. The moisture content of substrate affects emissions of methane (CH4) and nitrous oxide (N2O) from composting, but the scale and mechanisms behind these effects are poorly understood. This study examined effects of different moisture levels (44–66%) on CH4, N2O and carbon dioxide (CO2) emissions during 20 days of composting food and garden waste under controlled conditions (55 °C, 16% oxygen) in a 200-L reactor. Total CO2 emissions were 400–500 g CO2-C kg−1 initial C. Total CH4 emissions were highest, 35 g CH4-C kg−1 initial C, for the wettest substrate (66% moisture) and decreased exponentially with declining moisture content, with the lowest total emissions, 0.04 g CH4-C kg−1 initial C, observed with the driest substrate. Total N2O emissions were negatively correlated with moisture content, decreasing from 1.2 g N2O-N kg−1 initial N at 44% moisture to 0.3 g N2O-N kg−1 initial N at 59%, but the wettest substrate (66% moisture) had the highest N2O emissions, 1.4 g N2O-N kg−1 initial N. NH4-N accumulated in the wettest material, suggesting that the increased N2O emissions were due to reduced oxygen availability. The results indicate potential to reduce greenhouse gas emissions from large-scale composting by adjusting the moisture content at different stages of composting, thus lowering its overall environmental impact. This finding can be used in guidelines for large-scale composting process to avoid moisture conditions causing large greenhouse gas emissions.

  • 4.
    Ermolaev, Evgheni
    et al.
    Swedish Univ Agr Sci SLU, Dept Energy & Technol, Box 7032, SE-75007 Uppsala, Sweden..
    Sundberg, Cecilia
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure. Swedish Univ Agr Sci SLU, Dept Energy & Technol, Box 7032, SE-75007 Uppsala, Sweden..
    Pell, Mikael
    Swedish Univ Agr Sci SLU, Dept Mol Sci, Box 7015, SE-75007 Uppsala, Sweden..
    Smars, Sven
    Swedish Univ Agr Sci SLU, Dept Energy & Technol, Box 7032, SE-75007 Uppsala, Sweden..
    Jonsson, Håkan
    Swedish Univ Agr Sci SLU, Dept Energy & Technol, Box 7032, SE-75007 Uppsala, Sweden..
    Effects of moisture on emissions of methane, nitrous oxide and carbon dioxide from food and garden waste composting2019In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 240, article id UNSP 118165Article in journal (Refereed)
    Abstract [en]

    Globally, waste generation is continually increasing, with landfill as the main destination for biological waste. Composting is a simple alternative for handling waste, but when poorly managed poses a risk of greenhouse gas emissions. The moisture content of substrate affects emissions of methane (CH4) and nitrous oxide (N2O) from composting, but the scale and mechanisms behind these effects are poorly understood. This study examined effects of different moisture levels (44-66%) on CH4, N2O and carbon dioxide (CO2) emissions during 20 days of composting food and garden waste under controlled conditions (55 degrees C, 16% oxygen) in a 200-L reactor. Total CO2 emissions were 400-500 g CO2-C kg(-1) initial C. Total CH4 emissions were highest, 35 g CH4-C kg(-1) initial C, for the wettest substrate (66% moisture) and decreased exponentially with declining moisture content, with the lowest total emissions, 0.04 g CH4-C kg(-1) initial C, observed with the driest substrate. Total N2O emissions were negatively correlated with moisture content, decreasing from 1.2 g N2O-N kg(-1) initial N at 44% moisture to 0.3 g N2O-N kg(-1) initial N at 59%, but the wettest substrate (66% moisture) had the highest N2O emissions, 1.4 g N2O-N kg(-1) initial N. NH4-N accumulated in the wettest material, suggesting that the increased N2O emissions were due to reduced oxygen availability. The results indicate potential to reduce greenhouse gas emissions from large-scale composting by adjusting the moisture content at different stages of composting, thus lowering its overall environmental impact. This finding can be used in guidelines for large-scale composting process to avoid moisture conditions causing large greenhouse gas emissions. Elsevier Ltd. All rights reserved.

  • 5.
    Ferdous, Md Ruknul
    et al.
    IHE Delft Inst Water Educ, Dept Integrated Water Syst & Governance, NL-2611 AX Delft, Netherlands.;Univ Amsterdam, Fac Social & Behav Sci, NL-1012 WX Amsterdam, Netherlands..
    Wesselink, Anna
    IHE Delft Inst Water Educ, Dept Integrated Water Syst & Governance, NL-2611 AX Delft, Netherlands..
    Brandimarte, Luigia
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Slager, Kymo
    Deltares, NL-2600 MH Delft, Netherlands..
    Zwarteveen, Margreet
    IHE Delft Inst Water Educ, Dept Integrated Water Syst & Governance, NL-2611 AX Delft, Netherlands.;Univ Amsterdam, Fac Social & Behav Sci, NL-1012 WX Amsterdam, Netherlands..
    Di Baldassarre, Giuliano
    IHE Delft Inst Water Educ, Dept Integrated Water Syst & Governance, NL-2611 AX Delft, Netherlands.;Uppsala Univ, Dept Earth Sci, S-75236 Uppsala, Sweden.;CNDS, Ctr Nat Hazards & Disaster Sci, S-75236 Uppsala, Sweden..
    Socio-hydrological spaces in the Jamuna River floodplain in Bangladesh2018In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 22, no 10, p. 5159-5173Article in journal (Refereed)
    Abstract [en]

    Socio-hydrology aims to understand the dynamics and co-evolution of coupled human-water systems, with research consisting of generic models as well as specific case studies. In this paper, we propose a concept to help bridge the gap between these two types of socio-hydrological studies: socio-hydrological spaces (SHSs). A socio-hydrological space is a geographical area in a landscape. Its particular combination of hydrological and social features gives rise to the emergence of distinct interactions and dynamics (patterns) between society and water. Socio-hydrological research on human-flood interactions has found two generic responses, "fight" or "adapt". Distilling the patterns resulting from these responses in case studies provides a promising way to relate contextual specificities to the generic patterns described by conceptual models. Through the use of SHSs, different cases can be compared globally without aspiring to capturing them in a formal model. We illustrate the use of SHS for the Jamuna floodplain, Bangladesh. We use narratives and experiences of local experts and inhabitants to empirically describe and delimit SHS. We corroborated the resulting classification through the statistical analysis of primary data collected for the purpose (household surveys and focus group discussions) and secondary data (statistics, maps etc.). Our example of the use of SHSs shows that the concept draws attention to how historical patterns in the co-evolution of social behaviour, natural processes and technological interventions give rise to different landscapes, different styles of living and different ways of organising livelihoods. This provides a texture to the more generic patterns generated by socio-hydrological models, promising to make the resulting analysis more directly useful for decision makers. We propose that the usefulness of this concept in other floodplains, and for other socio-hydrological systems than floodplains, should be explored.

  • 6.
    Fiori, Aldo
    et al.
    Roma Tre Univ, Dept Engn, Rome, Italy..
    Zarlenga, Antonio
    Roma Tre Univ, Dept Engn, Rome, Italy..
    Bellin, Alberto
    Univ Trento, Dept Civil Environm & Mech Engn, Trento, Italy..
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Dagan, Gedeon
    Tel Aviv Univ, Sch Mech Engn, Ramat Aviv, Israel..
    Groundwater Contaminant Transport: Prediction Under Uncertainty, With Application to the MADE Transport Experiment2019In: FRONTIERS IN ENVIRONMENTAL SCIENCE, ISSN 2296-665X, Vol. 7, article id 79Article in journal (Refereed)
    Abstract [en]

    Transport of solutes in porous media at the laboratory scale is governed by an Advection Dispersion Equation (ADE). The advection is by the fluid velocity U and dispersion by D-dL = U alpha(dL), where the longitudinal dispersivity alpha(dL) is of the order of the pore size. Numerous data revealed that the longitudinal spreading of plumes at field scale is characterized by macrodispersivity alpha(L), larger than alpha(dL) by orders of magnitude. This effect is attributed to heterogeneity of aquifers manifesting in the spatial variability of the logconductivity Y. Modeling Y as a stationary random field and for mean uniform flow (natural gradient), alpha(L) could be determined in an analytical form by a first order approximation in sigma(2)(Y) (variance of Y) of the flow and transport equations. Recently, models and numerical simulations for solving transport in highly heterogeneous aquifers (sigma(2)(Y) > 1), primarily in terms of the mass arrival (the breakthrough curve BTC), were advanced. In all cases ergodicity, which allows to exchange the unknown BTC with the ensemble mean, was assumed to prevail for large plumes, compared to the logconductivity integral scale. Besides, the various statistical parameters characterizing the logconductivity structure as well as the mean flow were assumed to be known deterministically. The present paper investigates the uncertainty of the non-ergodic BTC due to the finiteness of the plume size as well as due to the uncertainty of the various parameters on which the BTC depends. By the use of a simplified transportmodel we developed in the past (which led to accurate results for ergodic plumes), we were able to get simple results for the variance of the BTC. It depends in an analytical manner on the flow parameters as well as on the dimension of the initial plume relative to the integral scale of logconductivity covariance. The results were applied to the analysis of the uncertainty of the plume spatial distribution of the MADE transport experiment. This was achieved by using the latest, recent, analysis of the MADE aquifer conductivity data.

  • 7.
    Gitau, K. J.
    et al.
    Univ Nairobi, Wangari Maathai Inst Peace & Environm Studies, POB 2905-0065, Nairobi, Kenya.;World Agroforestry Ctr ICRAF, POB 30677-00100, Nairobi, Kenya..
    Mutune, J.
    Univ Nairobi, Wangari Maathai Inst Peace & Environm Studies, POB 2905-0065, Nairobi, Kenya..
    Sundberg, Cecilia
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure. Swedish Univ Agr Sci SLU, Dept Energy & Technol, Uppsala, Sweden..
    Mendum, R.
    Penn State Univ, Off Int Programs, Coll Agr Sci, University Pk, PA 16802 USA..
    Njenga, M.
    Univ Nairobi, Wangari Maathai Inst Peace & Environm Studies, POB 2905-0065, Nairobi, Kenya.;World Agroforestry Ctr ICRAF, POB 30677-00100, Nairobi, Kenya..
    Factors influencing the adoption of biochar-producing gasifier cookstoves by households in rural Kenya2019In: Energy for Sustainable Development, ISSN 0973-0826, Vol. 52, p. 63-71Article in journal (Refereed)
    Abstract [en]

    Fuel wood is the main source of cooking and heating energy in developing countries. However, it is combusted in inefficient cookstoves, leading to more fuel use and human health problems resulting from exposure to smoke. Thus new, efficient cooking systems that can address some of these problems are required. This study examined gasifier cookstove use in Kwale County, Kenya, and factors influencing adoption. Gasifier stoves were issued for free to 50 households, which were surveyed after 2-3 months of use. The results showed that the stove was used by 96% of the households at varying frequencies, 40% of them used it almost every day with 4% switching to only using the new stove. All the users appreciated it because it saved fuel, produced less smoke, and produced charcoal to use for either cooking or soil amendment. Compared with the traditional three-stone open fire, the gasifier stove was reported to be easier to clean (98% of respondents), easier to adjust the heat (88%), easier to handle (58%), caused less exposure to heat (96%) and was cleaner for pots and the kitchen (98%). Another reported benefit of the gasifier stove was that it needed no tending (i.e., adjusting wood and blowing to keep the flames burning). The gasifier stove was mainly used to cook foods that required a short cooking time and many preferred to use it to cook dinner. However, the households encountered some challenges with using the gasifier stoves. For example, fuel preparation, reloading, and lighting were reported as challenges by 42%, 77% and 19%, respectively, of the 83% of households who reported challenges. These challenges could be overcome by improving stove design and by devising innovative ways of cutting fuel into small pieces. 2019 The Authors. Published by Elsevier Inc. on behalf of International Energy Initiative.

  • 8.
    Hamisi, Rajabu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Renman, Agnieszka
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Wörman, Anders
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Modelling Phosphorus Sorption Kinetics and the Longevity of Reactive Filter Materials Used for On-site Wastewater Treatment2019In: Water, Vol. 11, no 4, article id 811Article in journal (Refereed)
    Abstract [en]

    Use of reactive filter media (RFM) is an emerging technology in small-scale wastewater treatment to improve phosphorus (P) removal and filter material longevity for making this technology sustainable. In this study, long-term sorption kinetics and the spatial dynamics of sorbed P distribution were simulated in replaceable P-filter bags filled with 700 L of reactive material and used in real on-site treatment systems. The input data for model calibration were obtained in laboratory trials with Filtralite P®, Polonite® and Top16. The P concentration breakthrough threshold value was set at an effluent/influent (C/C0) ratio of 1 and simulations were performed with P concentrations varying from 1 to 25 mg L−1. The simulation results showed that influent P concentration was important for the breakthrough and longevity, and that Polonite performed best, followed by Top16 and Filtralite P. A 100-day break in simulated intermittent flow allowed the materials to recover, which for Polonite involved slight retardation of P saturation. The simulated spatial distribution of P accumulated in the filter bags showed large differences between the filter materials. The modelling insights from this study can be applied in design and operation of on-site treatment systems using reactive filter materials

  • 9.
    Hamisi, Rajabu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Renman, Agnieszka
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Wörman, Anders
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Phosphorus sorption and leaching in sand filters used for onsite wastewater treatment - a column experimentIn: Article, book review (Refereed)
    Abstract [en]

    The sorption capacities of filter sands used for onsite wastewater treatment and their associated risks of phosphorus (P) leakage on contact with rainwater were investigated in column experiments and modelling studies. Columns packed with sand were exposed to real domestic wastewater of different characteristics and hydraulic loading modes. The wastewater fed into the columns was effluent collected from three different treatment units in the field: a septic tank (ST), biofiltration tank (BF) and Polonite® filter bag (PO). The risk of P leaching to groundwater and surface water was also assessed, by exposing the same sand columns to artificial rainwater. The results indicated that sand columns can exhibit different adsorption capacities for Total-P, phosphate-P and total suspended solids, depending on the characteristics of influent wastewater. The adsorption capacity increased in the order ST > BF > PO, based on availability of organic matter to form biofilm. Effluent from Pol columns was significantly clearer, indicating lower organics content, than effluent from ST and BF columns. The modelled breakthrough curves for Total-P desorption agreed satisfactorily with the measured values, but further model improvement is needed.

  • 10.
    Hamisi, Rajabu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Renman, Agnieszka
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Wörman, Anders
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Simulating the hydraulic dynamics and treatment performance of a sequencing batch flow constructed wetlandIn: Article, book review (Refereed)
    Abstract [en]

    In a six-month field trial, the performance of a full-scale sequencing batch flow constructed wetland (SBCW) treating on-site wastewater was determined. The filling and draining periods lasted 5-9 days, depending on wastewater production by users (two households). The results indicated that the SBCW system efficiently removed ammonium-nitrogen (NH4-N, 76%) and Escherichia coli (89%). However, draining by pumping increased preferential water flow and considerably limited removal of dissolved phosphorus (PO4-P) in the filter bed. Analysis of water samples from nine points and three vertical levels of the wetland bed showed that pumping aerated the bed, resulting in removal of NH4-N being highest in the top 0-0.2 m layer (43%) intermediate in the 0.2-0.4 m layer (32%), and lowest in the deep (0.4-0.6 m) layer (4%). Complementary modeling using COMSOL Multiphysics software to predict the hydraulic dynamics for three different SBCW designs indicated that the drainage system of the present SBCW should be re-designed to increase contact time and aeration, for improved phosphorus and nitrogen removal.

  • 11.
    Henryson, Kajsa
    et al.
    Swedish Univ Agr Sci SLU, Dept Energy & Technol, POB 7032, S-75007 Uppsala, Sweden..
    Hansson, Per-Anders
    Swedish Univ Agr Sci SLU, Dept Energy & Technol, POB 7032, S-75007 Uppsala, Sweden..
    Sundberg, Cecilia
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure. Swedish Univ Agr Sci SLU, Dept Energy & Technol, POB 7032, S-75007 Uppsala, Sweden.
    Spatially differentiated midpoint indicator for marine eutrophication of waterborne emissions in Sweden2018In: The International Journal of Life Cycle Assessment, ISSN 0948-3349, E-ISSN 1614-7502, Vol. 23, no 1, p. 70-81Article in journal (Refereed)
    Abstract [en]

    In life cycle assessment (LCA), eutrophication is commonly assessed using site-generic characterisation factors, despite being a site-dependent environmental impact. The purpose of this study was to improve the environmental relevance of marine eutrophication impact assessment in LCA, particularly regarding the impact assessment of waterborne nutrient emissions from Swedish agriculture. Characterisation factors were derived using site-dependent data on nutrient transport for all agricultural soils in Sweden, divided into 968 catchment areas, and considering the Baltic Sea, the receiving marine compartment, as both nitrogen- and phosphorus-limited. These new characterisation factors were then applied to waterborne nutrient emissions from typical grass ley and spring barley cultivation in all catchments. The site-dependent marine eutrophication characterisation factors obtained for nutrient leaching from soils varied between 0.056 and 0.986 kg N-eq/kg N and between 0 and 7.23 kg N-eq/kg P among sites in Sweden. On applying the new characterisation factors to spring barley and grass ley cultivation at different sites in Sweden, the total marine eutrophication impact from waterborne nutrient emissions for these crops varied by up to two orders of magnitude between sites. This variation shows that site plays an important role in determining the actual impact of an emission, which means that site-dependent impact assessment could provide valuable information to life cycle assessments and increase the relevance of LCA as a tool for assessment of product-related eutrophication impacts. Characterisation factors for marine eutrophication impact assessment at high spatial resolution, considering both the site-dependent fate of eutrophying compounds and specific nutrient limitations in the recipient waterbody, were developed for waterborne nutrient emissions from agriculture in Sweden. Application of the characterisation factors revealed variations in calculated impacts between sites in Sweden, highlighting the importance of spatial differentiation of characterisation modelling within the scale of the impact.

  • 12.
    Kivimaa, Paula
    et al.
    Science Policy Research Unit SPRU, University of Sussex; Finnish Environment Institute.
    Kangas, Hanna-Liisa
    Finnish Environment Institute.
    Lazarevic, David
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure. Finnish Environment Institute.
    Client-oriented evaluation of ‘creative destruction’in policy mixes: Finnish policies on building energy efficiency transition2017In: Energy Research & Social Science, Vol. 33, p. 115-127Article in journal (Refereed)
  • 13.
    Kordas, Olga
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Gourjii, A.
    Nikiforovich, E.
    Cherniy, D.
    A study on mathematical short-term modelling of environmental pollutant transport by sea currents: The lagrangian approach2017In: Journal of Environmental Accounting and Management, ISSN 2325-6192, E-ISSN 2325-6206, Vol. 5, no 2, p. 87-104Article in journal (Refereed)
    Abstract [en]

    This paper deals with short-term modelling of pollutant transport on the sea surface after environmental accidents. Using the Lagrangian approach, a two-dimensional model of pollutant flow is developed to determine the average velocity field of the flow in the presence of tidal currents and sea surface wind stress for an arbitrarily shaped coastline. This approach assumes that the main transport mechanism is convection. Short-term scenarios are considered, where diffusion effects on pollutant transport can be neglected. The hydrodynamic problem is solved by the method of discrete singularities adapted to fluid advection problems. The problem of environmental pollutant transport by sea currents is reduced to integration of the advection equations to determine the spatio-temporal properties of the spreading pollution. The model was verified through comparison of the results against natural observations on the spread of an oil spill on the sea surface following a collision between the Chinese bulk carrier Fu Shan Hai and the Cyprian container ship Gdynia near the island of Bornholm in the Baltic Sea (May 31, 2003). Satisfactory agreement was found between results of a 7-day numerical simulation and observed data. The proposed model can therefore be used for real-time prediction of short-term pollutant transport on a sea surface with an arbitrarily shaped coastline, to support decision-making processes during maritime accidents, in particular oil spills.

  • 14.
    Lazarevic, David
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure. Finnish Environment Institute, Environmental Policy Centre, Finland.
    Valve, Helena
    Narrating expectations for the circular economy: towards a common and contested European transition2017In: Energy Research & Social Science, ISSN 2214-6296, E-ISSN 2214-6326, Vol. 31, p. 60-69Article in journal (Refereed)
    Abstract [en]

    The European Union (EU) has set its sights on becoming a circular economy, envisaging a transition that implies systemic changes in natural resource transformations and material flows; and offering a response to what is commonly labelled as the ‘take-make-dispose’ conventional economic model. What does the transition toward a circular economy entail and what can it do? This paper analyses the emergence and mobilisation of expectations that are shaping the EU transition to a circular economy. It traces the narrative elements through which the circular economy is configured through an analysis of position papers presented to inform the debate on the European Commission’s circular economy package. Expectations for the circular economy are articulated as: (1) a perfect circle of slow material flows; (2) a shift from consumer to user; (3) growth through circularity and decoupling; and (4) a solution to European renewal. Extending boundaries of what is ‘in’ benefits actors driving the circular economy as, in the short-term, they can actively support a deliberately vague, but uncontroversial, circular economy. On the one hand, the expectations present a strong sense of a collective ‘we’, on the other hand we are yet to see the contentions and contestations being full playing out

  • 15.
    Levi, Lea
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Destouni, Georgia
    Data-driven analysis of nutrient inputs and transfers through nested catchments2018In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 610, p. 482-494Article in journal (Refereed)
  • 16. Lin, C.
    et al.
    Kao, M. -J
    Yang, James
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Teng, P. -H
    Raikar, R. V.
    Study on probabilistic mean features of lower and upper free-surface profiles and velocity fields of a highly fluctuating free jet over a chute2018In: Journal of Marine Science and Technology (Taiwan), ISSN 1023-2796, Vol. 26, no 3, p. 309-326Article in journal (Refereed)
    Abstract [en]

    An optic-based method that utilizes the particle-laden images captured during high-speed particle image velocimetry (HSPIV) measurements is presented, aiming to explore the probabilistic mean characteristics of the free surface profiles and velocity fields of a free jet with high-frequency random fluctuations over a chute. The technique based on the gray-level gradients in the smoothed gray level distribution of the contrast-enhanced images is used to determine the probabilistic mean features of the free jet, right beneath and above which the water-air interfaces have I%/(100 I)% intermittent appearance of air/water phase and (100 I)% /I% fitful show-up of water/air phase. Further, the cross-correlation calculation for HSPIV measurements is employed to obtain the instantaneous and probabilistic mean velocity fields of the free jet. A target experiment of the free jet having a mean water-depth of 2.76 cm and a Froude number of 3.92 over a 17 chute model is performed in a re-circulating water channel to demonstrate the application of this method. The entire process for obtaining the probabilistic mean positions of the free surface profiles is elucidated step-by step. The lower/upper part of the free surface changing from the height at which the possibility of intermittent appearance of water phase is 3%/97%, via the counterpart for 50%/50%, to that for 97%/ 3% is identified precisely. In addition, the probabilistic mean velocity field is further categorized into the conditionally and overall time-averaged ones. Each streamwise velocity profile in the conditionally time-averaged velocity field is fairly uniform. However, the counterpart in the overall time-averaged velocity field evidently shows the non-uniform feature with prominent velocity gradient in the lower/upper part between the height at which the possibility of intermittent appearance of water phase is 3%/97% and the counterpart is 97%/3%.

  • 17.
    Molinari, Marco
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Kordas, Olga
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    ICT in the built environment: drivers, barriers and uncertainties2017In: Biennial International Workshop Advances in Energy Studies: BIWAES, Graz, 2017Conference paper (Other academic)
    Abstract [en]

    Buildings are major contributors to energy use and environmental impact in developed societies. If theambitious sustainability targets of modern societies are to be met, energy use in the built environmentmust be addressed as a central issue.New momentum on achieving energy efficiency in the building sector has been triggered by informationand communication technology (ICT). New opportunities bringing the concept of smart building closerto reality are offered e.g. by innovative sensing techniques, extensive and cost-efficient data collectionand analysis, advanced controls and artificial intelligence.However, these opportunities are associated with cost and uncertainties regarding whether theinvestment costs are paid back in terms of energy savings, whether indoor comfort and air quality andimproved, the drawbacks in term of increased maintenance effort, complexity, reliability and resilience,the effects in terms of user interaction, how data security is affected and the long-term effects on society.This paper critically analyses recent research findings and reviews the pros and cons of some promisingICT techniques being applied in the building sector. It exemplifies drivers and barriers to implementationof advanced controls and artificial intelligence in buildings, based on findings from two test-beds inStockholm, and discusses the implications of these findings for future research.

  • 18.
    Nilsson, Anders
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Stoll, Pia
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Brandt, Nils
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Assessing the impact of real-time price visualization on residential electricity consumption, costs, and carbon emissions2015In: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 124, p. 152-161Article in journal (Refereed)
    Abstract [en]

    The development of smart grid projects, with demand side management as an integral part, has led to an increased interest of households’ willingness to react to different types of demand response programs. This paper presents a pilot study assessing the impact of real-time price visualization on residential electricity consumption, and its effects on electricity costs and carbon (CO2eq) emissions. We analyze changes in electricity consumption based on a test group and a reference group of 12 households, respectively. To allow for analysis on load shift impact on CO2eq emissions, hourly dynamic CO2eq intensity of the Swedish electricity grid mix is calculated, using electricity generation data, trading data, and fuel-type specific emission factors. The results suggest that, on average, the test households shifted roughly 5% of their total daily electricity consumption from peak hours (of high electricity price) to off-peak hours (of low electricity price) as an effect of real-time price visualization. However, due to the mechanisms of the Swedish electricity market, with a negative relation between spot price and CO2eq intensity, the load shift led to a split effect; electricity costs modestly decreased while CO2eq emissions increased. In addition, any indication of the contribution of real-time spot price visualization to a reduction in overall household electricity consumption level could not be found, as the relative difference in consumption level between the test households and the reference households remained constant during both the baseline period and the test period. 

  • 19.
    Nilsson, Anders
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Wester, Misse
    Lazarevic, David
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Brandt, Nils
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Smart homes, home energy management systems and real-time feedback- Lessons for influencing household energy consumption from a Swedish field study2018In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 179, p. 15-25Article in journal (Refereed)
    Abstract [en]

    Home energy management systems (HEMS), providing energy feedback and smart features through in-home displays, have the potential to support more sustainable household decisions concerning energy consumption. However, recent findings from European smart metering trials have reduced the optimism, suggesting only modest savings from energy feedback. In this paper, we investigate the potential of HEMS to foster reductions in energy use, focusing on a population segment of particular relevance; high-income and highly educated households, considered as early adopters of smart grid technologies. Covering 154 households participating in a field trial in a sustainable city district in Stockholm, Sweden during one year, this study draws on the analyses of smart meter electricity and hot tap water data and in-depth interviews to provide an increased understanding of how feedback and features are perceived, used, and acted upon, and resulting effects on awareness, behavior, and consumption. Our results show that impact on energy consumption varies widely across individual households, suggesting that households respond to energy feedback highly individually. Although HEMS may lead to increased awareness of energy consumption, as well as increased home comfort, several obstacles for energy consumption behavioral change are identified. Drawing from these findings, we suggest policy implications and key issues for future research.

  • 20.
    Pasichnyi, Oleksii
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Levihn, Fabian
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Sustainability and Industrial Dynamics.
    Shahrokni, Hossein
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Wallin, Jörgen
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration. KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Sustainable Building Systems. KTH Royal Inst Technol, Dept Energy Technol ETT, Res Grp Urban Analyt & Transit UrbanT, Brinellvagen 68, S-10144 Stockholm, Sweden..
    Kordas, Olga
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. KTH Royal Inst Technol, Dept Sustainable Dev Environm Sci & Engn SEED, Res Grp Urban Analyt & Transit UrbanT, Tekn Ringen 10b, S-10044 Stockholm, Sweden..
    Data-driven strategic planning of building energy retrofitting: The case of Stockholm2019In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 233, p. 546-560Article in journal (Refereed)
    Abstract [en]

    Limiting global warming to 1.5 degrees C requires a substantial decrease in the average carbon intensity of buildings, which implies a need for decision-support systems to enable large-scale energy efficiency improvements in existing building stock. This paper presents a novel data-driven approach to strategic planning of building energy retrofitting. The approach is based on the urban building energy model (UBEM), using data about actual building heat energy consumption, energy performance certificates and reference databases. Aggregated projections of the energy performance of each building are used for holistic city-level analysis of retrofitting strategies considering multiple objectives, such as energy saving, emissions reduction and required social investment. The approach is illustrated by the case of Stockholm, where three retrofitting packages (heat recovery ventilation; energy-efficient windows; and a combination of these) were considered for multi-family residential buildings constructed 1946-1975. This identified potential for decreasing heat demand by 334 GWh (18%) and consequent emissions reduction by 19.6 kt-CO2 per year. The proposed method allows the change in total energy demand from large-scale retrofitting to be assessed and explores its impact on the supply side. It thus enables more precisely targeted and better coordinated energy efficiency programmes. The case of Stockholm demonstrates the potential of rich urban energy datasets and data science techniques for better decision making and strategic planning.

  • 21.
    Pasichnyi, Oleksii
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Wallin, Jörgen
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Kordas, Olga
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Data-driven building archetypes for urban building energy modelling2019In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 181, p. 360-377Article in journal (Refereed)
    Abstract [en]

    This paper presents an approach for using rich datasets to develop different building archetypes depending on the urban energy challenges addressed. Two cases (building retrofitting and electric heating) were analysed using the same city, Stockholm (Sweden), and the same input data, energy performance certificates and heat energy use metering data. The distinctive character of these problems resulted in different modelling workflows and archetypes being developed. The building retrofitting case followed a hybrid approach, integrating statistical and physical perspectives, estimating energy savings for 5532 buildings from seven retrofitting packages. The electric heating case provided an explicitly statistical data-driven view of the problem, estimating potential for improvement of power capacity of the local electric grid at peak electric power of 147 MW. The conclusion was that the growing availability of linked building energy data requires a shift in the urban building energy modelling (UBEM) paradigm from single-logic models to on-request multiple-purpose data intelligence services.

  • 22.
    Pasichnyi, Oleksii
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Wallin, Jörgen
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Levihn, Fabian
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.). AB Stockholm Exergi, Sweden.
    Shahrokni, Hossein
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Kordas, Olga
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Energy performance certificates — New opportunities for data-enabled urban energy policy instruments?2019In: Energy Policy, ISSN 0301-4215, E-ISSN 1873-6777, p. 486-499Article in journal (Refereed)
    Abstract [en]

    Energy performance certificates (EPC) were introduced in European Union to support reaching energy efficiency targets by informing actors in the building sector about energy efficiency in buildings. While EPC have become a core source of information about building energy, the domains of its applications have not been studied systematically. This partly explains the limitation of conventional EPC data quality studies that fail to expose the essential problems and secure effective use of the data. This study reviews existing applications of EPC data and proposes a new method for assessing the quality of EPCs using data analytics. Thirteen application domains were identified from systematic mapping of 79 papers, revealing increases in the number and complexity of studies and advances in applied data analysis techniques. The proposed data quality assurance method based on six validation levels was tested using four samples of EPC dataset for the case of Sweden. The analysis showed that EPC data can be improved through adding or revising the EPC features and assuring interoperability of EPC datasets. In conclusion, EPC data have wider applications than initially intended by the EPC policy instrument, placing stronger requirements on the quality and content of the data.

  • 23.
    Pereverza, Kateryna
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Steering sustainability transitions? Modular participatory backcasting for strategic planning in the heating and cooling sector2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Fostering sustainability transitions in the heating and cooling sector is a necessary and urgent issue. Steering mechanisms can enable coordination of actions by different actors towards common sustainability goals. Previous studies have identified requirements relevant for such steering frameworks, but have not specifically addressed planning in the highly contextual heating and cooling sector. Participatory backcasting (PB) possesses a number of relevant characteristics for use as a planning framework in this sector, but its adaptability and potential impact first need to be addressed.

    This thesis sought to advance strategic planning in the heating and cooling sector by improving the adaptability, transparency and reflexivity of PB processes and extending their impact beyond individuals directly involved, so-called social scales of impact. Key research objectives of the present work were to: (1) develop a strategic planning framework for the heating and cooling sector based on PB and examine its adaptability to local contexts, (2) develop methods for scenario development, selection and analysis to allow for co-informing between modelling and participatory processes within PB-based strategic planning, and (3) identify factors that could influence the social scales of the impact of participatory strategic planning processes.

    Objectives 1 and 2 were pursued in a multiple case study involving transdisciplinary research over one-year PB-based planning processes in Bila Tserkva, Ukraine (Case I) and Niš, Serbia (Case II). The social scales of impact (Objective 3) were studied in a single case – a Swedish project aimed at advancing the practice of long-term planning in regions ‘Region 2050’ (Case III). In all cases, both theoretical and empirical research were conducted.

    The study proposes a novel framework, modular participatory backcasting (mPB), for strategic planning in the heating and cooling sector. The framework integrates principles of modularity, participatory modelling, and transdisciplinarity. The results of mPB implementation in Case I and Case II suggest that the framework has acceptable adaptability to local contexts. Greater reflexivity and transparency in the scenario development, selection and analysis were achieved by developing a morphological method and implementation of participatory modelling approaches. Finally, boundary spanning individuals, collaborations and institutional plurality were identified in Case III as important factors for broadening the social scales of impact of participatory strategic planning processes.

  • 24.
    Pereverza, Kateryna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Kordas, Olga
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Sustainability through stakeholder learning: Participatory backcasting for the heating sector2017In: 10th BIWAES Biennial International Workshop Advances in Energy Studies: Energy futures, environment and well-being / [ed] Sergio Ulgiati and Laura Vanoli, Budapest, 2017Conference paper (Refereed)
    Abstract [en]

    Social learning is an important element of the reflexive governance approaches needed to enable sustainability transitions. One such approach is participatory backcasting (PB), which involves development of a desirable future vision and a pathway towards this vision. Social learning has been reported as an outcome of different PB projects, including those performed in the infrastructure sector. This study examined the importance of sharing and transferring knowledge and new perceptions developed during PB projects among the individuals directly involved in these projects to and within their formal and informal groups and organisations (e.g. local authorities, DH companies, equipment producers, consumer associations). Mechanisms that need to be incorporated into PB processes to support knowledge sharing/transfer were identified as: (1) use of actor role profiles to identify individuals with bridging/connecting/change agent capability for inclusion in a PB process; (2) strong participant engagement in co-creation activities during the PB project; and (3) PB process design to achieve the multiplier effect (e.g. capacity-building workshops for local researchers and authorities). These mechanisms were successfully tested using the case of two PB-based projects seeking sustainability in the heating sector of the Ukrainian city Bila Tserkva and the Serbian city Niš. It was concluded that further investigation of mechanisms for knowledge sharing/transfer and experimentation within PB processes is a promising research area for enabling sustainability transitions in the heating sector.

  • 25.
    Rasul, Hedi
    et al.
    Koya University.
    Zou, Liangchao
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Olofsson, Bo
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Monitoring of moisture and salinity content in an operational road structure by electrical resistivity tomography.In: Near Surface Geophysics, ISSN 1569-4445, E-ISSN 1873-0604Article in journal (Refereed)
    Abstract [en]

    Moisture dynamics in road systems significantly affect road structure design and maintenance. This study analysed moisture dynamics in a cross-section of motorway (the E18) in Sweden during a one-year period through in situ monitoring using electrical resistivity tomography (ERT). The monitoring methodology was assessed since resistivity can provide a good proxy for monitoring moisture in the road structure. Monthly electrical resistivity was calculated by inverting resistivity data along a pre-installed electrical resistivity line beneath the surface asphalt layer of the road at the test site. The electrical resistivity data were then statistically analysed and correlated with local climate data, i.e. precipitation and temperature, and with ground parameters such as moisture content. The results showed high variation in resistivity in the road surface layer and road shoulders depending on weather conditions, water flow and other surface activities. In general, negative correlations between electrical resistivity and precipitation were observed. The results also indicated possible retardation of de-icing salt after accumulating in the top layer during winter. These findings advance understanding of the moisture dynamics in roads and can help improve pavement design in response to future climate change.

  • 26.
    Refsgaard, Jens Christian
    et al.
    Geol Survey Denmark & Greenland, Copenhagen, Denmark..
    Hansen, Anne L.
    LandboSyd, Aabenraa, Denmark..
    Hojberg, Anker L.
    Geol Survey Denmark & Greenland, Copenhagen, Denmark..
    Olesen, Jorgen E.
    Aarhus Univ, Dept Agroecol, Tjele, Denmark..
    Hashemi, Fatemeh
    Aarhus Univ, Dept Biosci, Silkeborg, Denmark..
    Wachniew, Przemyslaw
    AGH Univ Sci & Technol, Krakow, Poland..
    Wörman, Anders
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Bartosova, Alena
    Swedish Meteorol & Hydrol Inst, Norrkoping, Sweden..
    Stelljes, Nico
    Ecol Inst, Berlin, Germany..
    Chubarenko, Boris
    Russian Acad Sci, Shirshov Inst Oceanol, Moscow, Russia..
    Spatially differentiated regulation: Can it save the Baltic Sea from excessive N-loads?2019In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 48, no 11, p. 1278-1289Article in journal (Refereed)
    Abstract [en]

    The Baltic Sea Action Plan and the EU Water Framework Directive both require substantial additional reductions of nutrient loads (N and P) to the marine environment. Focusing on nitrogen, we present a widely applicable concept for spatially differentiated regulation, exploiting the large spatial variations in the natural removal of nitrate in groundwater and surface water. By targeting mitigation measures towards areas where nature's own capacity for removal is low, spatially differentiated regulation can be more cost-effective than the traditional uniform regulation. We present a methodology for upscaling local modelling results on targeted measures at field scale to Baltic Sea drainage basin scale. The paper assesses the potential gain and discusses key challenges related to implementation of spatially differentiated regulation, including the need for more scientific knowledge, handling of uncertainties, practical constraints related to agricultural practice and introduction of co-governance regimes.

  • 27.
    Ríos Bayona, Francisco
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stigsson, Martin
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure. SKB, Swedish Nuclear Fuel and Waste Management Co.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Mas Ivars, Diego
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. SKB, Swedish Nuclear Fuel and Waste Management Co.
    Comparison between shear strength based on Barton’s roughness profiles and equivalent synthetic profiles based on fractal theory2018In: 52nd U.S. Rock Mechanics/Geomechanics Symposium, American Rock Mechanics Association (ARMA) , 2018Conference paper (Refereed)
    Abstract [en]

    A comprehensive understanding of the shear strength and the mechanical behavior of rock joints is to some extent still missing today. Several attempts have been made to develop empirical and analytical shear strength criteria that explain this mechanism. One of the most important parameters governing the shear strength of rock fractures is the surface roughness, which is generally determined using the Joint Roughness Coefficient (JRC). This parameter is often determined subjectively in the field by comparison with 10 predefined roughness profiles. Recent studies indicate that surface roughness can be accurately represented by using fractal analysis. The aim of this study is to perform a first attempt to investigate the mechanical equivalence in terms of the peak shear strength between synthetic rock fractures, where the surface roughness has been generated using fractal theory, and standard roughness profiles from Barton and Choubey, 1977, using the particle flow code PFC2D. The results from the numerical shear tests under constant normal load (CNL) are compared with the predicted peak shear strength using Barton’s criterion and a back-calculation of the JRC value is carried out.

  • 28.
    Shamu, John
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Zou, Liangchao
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Håkansson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. Skanska Sweden AB.
    Cementbaserade Injekteringsmedels Reogram: Instabilt Flöde Och Inverkan På Injektering2019In: Proceedings Bergdagarna 2019, Stockholm, 2019Conference paper (Other academic)
  • 29.
    Shamu, John
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Zou, Liangchao
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Kotzé, Reinhardt
    Incipientus Ultrasound Flow Technologies AB, Sweden.
    Wiklund, Johan
    Incipientus Ultrasound Flow Technologies AB, Sweden.
    Håkansson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. Skanska Sweden AB, Sweden.
    Radial Flow Velocity Profiles of a Yield Stress Fluid between Smooth Parallel DisksManuscript (preprint) (Other academic)
  • 30.
    Soltani, Safeyeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Quantifying the distribution of tracer discharge from boreal catchments under transient flow using the kinematic pathway approach2017In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 53, no 7, p. 5659-5676Article in journal (Refereed)
    Abstract [en]

    This focuses on solute discharge from boreal catchments with relatively shallow groundwater table and topography-driven groundwater flow. We explore whether a simplified semianalytical approach can be used for predictive modeling of the statistical distribution of tracer discharge. The approach is referred to as the "kinematic pathways approach'' (KPA). This approach uses hydrological and tracer inputs and topographical and hydrogeological information; the latter regards average aquifer depth to the less permeable bedrock. A characteristic velocity of water flow through the catchment is further obtained from the overall water balance in the catchment. For the waterborne tracer transport through the catchment, morphological dispersion is accounted for by topographical analysis of the distribution of pathway lengths to the catchment outlet. Macrodispersion is accounted for heuristically by assuming an effective Peclet number. Distribution of water travel times through the catchment reflect the dispersion on both levels and are derived in both a forward mode (transit time from input to outlet) and a backward mode (water age when arriving at outlet arrival). The forward distribution of water travel times is further used for the tracer discharge modeling by convolution. The approach is applied to modeling of a 23 year long chloride data series for a specific catchment Kringlan (Sweden), and for generic modeling to better understand the dependence of the tracer discharge distribution on different dispersion aspects. The KPA is found to provide reasonable estimates of tracer discharge distribution, and particularly of extreme values, depending on method for determining the pathway length distribution. As a possible alternative analytical model of tracer transport through a catchment, the reservoir approach generally results in large tracer dispersion. This implies that tracer discharge distributions obtained from a mixed reservoir approach and from KPA are only compatible under large dispersion conditions.

  • 31.
    Soltani, Safeyeh Sofie
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Contaminant attenuation by shallow aquifer systems under steady flow2017In: Advances in Water Resources, ISSN 0309-1708, E-ISSN 1872-9657, Vol. 108, p. 157-169Article in journal (Refereed)
    Abstract [en]

    We present a framework for analyzing advection-dominated solute transport and transformation in aquifer systems of boreal catchments that are typically shallow and rest on crystalline bedrock. A methodology is presented for estimating tracer discharge based on particle trajectories from recharge to discharge locations and computing their first passage times assuming that the flow pattern is approximately steady-state. Transformation processes can be included by solving one-dimensional reactive transport with randomized water travel time as the independent variable; the distribution of the travel times incorporates morphological dispersion (due to catchment geometry/topography) as well as macro-dispersion (due to heterogeneity of underlying hydraulic properties). The implementation of the framework is illustrated for the well characterized coastal catchment of Forsmark (Sweden). We find that macro-dispersion has a notable effect on attenuation even though the morphological dispersion is significantly larger. Preferential flow on the catchment scale is found to be considerable with only 5% of the Eulerian velocities contributing to transport over the simulation period of 375 years. Natural attenuation is illustrated as a simple (linear decay) transformation process. Simulated natural attenuation can be estimated analytically reasonably well by using basic hydrological and structural information, the latter being the pathway length distribution and average aquifer depth to the bedrock.

  • 32.
    Stigsson, Martin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. SKB, Swedish Nuclear Fuel and Waste Management Co.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure. SKB, Swedish Nuclear Fuel and Waste Management Co.
    Ivars, Diego Mas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. SKB, Swedish Nuclear Fuel and Waste Management Co.
    Selroos, Jan-Olof
    SKB, Swedish Nuclear Fuel and Waste Management Co.
    A method to estimate flow and transport properties of sheared synthetic fractures in crystalline rock with different roughness under varying normal stressManuscript (preprint) (Other academic)
  • 33.
    Teng, Penghua
    et al.
    KTH, School of Architecture and the Built Environment (ABE).
    Yang, James
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    CFD modeling of two-phase flow of a spillwaychute aerator of large width2016In: Journal of Applied Water Engineering and Research, ISSN 2324-9676, E-ISSN 2324-9676, Vol. 4, no 2, p. 163-177Article in journal (Refereed)
    Abstract [en]

    An aerator is frequently used to prevent cavitation damages in high-velocity spillways. To understand its characteristics,one often resorts to physical model tests. To complement physical model tests, computation fluid dynamics simulations areused to determine water–air flow behaviors.With Bergeforsen’s 35 m wide aerator, numerical modeling has been performedto evaluate its performance and improve its configuration. The parameters of interest include spillway discharge capacity,air entrainment rate, duct subpressure and air concentration in the aerated flow. The simulated discharge capacity agreesreasonably with experimental data. Due to the larger chute width, empirical formulas do not reasonably predict the airdemand. To provide the air required by the aerator, its distribution in the cavity must be guaranteed. We thus looked into theair supply system and the air flux in the cavity to improve the aerator function. Larger vent openings in the middle of thechute are preferable for large-width aerators.

  • 34.
    Teng, Penghua
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Yang, James
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Modeling and Prototype Testing of Flows over Flip-Bucket Aerators2018In: Journal of Hydraulic Engineering, ISSN 0733-9429, E-ISSN 1943-7900, Vol. 144, no 12, article id 04018069Article in journal (Refereed)
    Abstract [en]

    The paper deals with a unique spillway which incorporates an aerator in each flip bucket with the intention to aerate the flow and avoid subatmospheric air cavities enclosed by the jets. In terms of jet breakup and stability, the physical models and the prototype lead to contradicting conclusions. With sealed aerators, the models exhibit intact air cavities featuring negative air pressure, suggesting the aeration need. Computational fluid dynamics (CFD) is performed to determine the reason for the discrepancy. Both the prototype observations and CFD indicate that the jets break up as a result of air entrainment; the resulting cavity air-pressure drops are insignificantly small. The discrepancy is due to the small model scale, in which the threshold flow velocity for air entrainment is not met and the prerequisite for jet breakup does not exist. To correctly reproduce similar water-air flow phenomena, the model should be large enough to meet the air-entrainment criterion. When questioning a small-scale model with air-cavity formation, CFD simulations should be performed to check the model results and make corrections, if needed.

  • 35.
    Teng, Penghua
    et al.
    KTH, School of Architecture and the Built Environment (ABE).
    Yang, James
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Modeling and Prototype Testing of Flowsover Flip-Bucket Aerators2018In: Journal of Hydraulic Engineering, ISSN 0733-9429, E-ISSN 1943-7900, Vol. 144, no 12Article in journal (Refereed)
    Abstract [en]

    The paper deals with a unique spillway which incorporates an aerator in each flip bucket with the intention to aerate the flow andavoid subatmospheric air cavities enclosed by the jets. In terms of jet breakup and stability, the physical models and the prototype lead tocontradicting conclusions. With sealed aerators, the models exhibit intact air cavities featuring negative air pressure, suggesting the aerationneed. Computational fluid dynamics (CFD) is performed to determine the reason for the discrepancy. Both the prototype observations andCFD indicate that the jets break up as a result of air entrainment; the resulting cavity air-pressure drops are insignificantly small. The discrepancyis due to the small model scale, in which the threshold flow velocity for air entrainment is not met and the prerequisite for jet breakupdoes not exist. To correctly reproduce similar water–air flow phenomena, the model should be large enough to meet the air-entrainmentcriterion. When questioning a small-scale model with air-cavity formation, CFD simulations should be performed to check the model resultsand make corrections, if needed.

  • 36.
    Teng, Penghua
    et al.
    KTH, School of Architecture and the Built Environment (ABE).
    Yang, James
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Pfister, Michael
    Ecole Polytechnique Federale de Lausanne (EPFL).
    Studies of Two-Phase Flow at a Chute Aeratorwith Experiments and CFD Modelling2016In: Modelling and Simulation in Engineering, ISSN 1687-5591, E-ISSN 1687-5605, article id 4729128Article in journal (Refereed)
    Abstract [en]

    The chute aerator of a spillway is a structure in such a sense that air is, in the intense emulsification, entrained into the highvelocitywater flow. Correctly predicting the air entrainment and two-phase flow pattern at the aerator would contribute to reliablespillway operation. Based on experimental data, 2D numerical simulations are preformed to predict streamwise air concentrationsin the aerated flow, in which a two-fluid model is used. Depending on the air bubble size, relatively good agreement is seen withthe experiments in the air cavity zone. The simulations give rise to higher air concentration downstream of the cavity, which ispresumably due to underestimation of the interfacial forces in the two-fluid model.

  • 37.
    Torabi Haghighi, A.
    et al.
    Water, Energy and Environmental Engineering Research Unit, University of Oulu, PO Box 4300, 90014, Finland.
    Ashraf, F. B.
    Water, Energy and Environmental Engineering Research Unit, University of Oulu, PO Box 4300, 90014, Finland.
    Riml, Joakim
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Koskela, J.
    Finnish Environment Institute (SYKE), Latokartanonkaari 11, Helsinki 00790, Finland.
    Kløve, B.
    Water, Energy and Environmental Engineering Research Unit, University of Oulu, PO Box 4300, 90014, Finland.
    Marttila, H.
    Water, Energy and Environmental Engineering Research Unit, University of Oulu, PO Box 4300, 90014, Finland.
    A power market-based operation support model for sub-daily hydropower regulation practices2019In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 255, article id 113905Article in journal (Refereed)
    Abstract [en]

    With increasing power production from renewable energy sources, sub-daily variations in energy demand need to be balanced. Today, hydropower is commonly used as balancing power. In this study, we quantified the impact of capacity constraints, in terms of reservoir volume and hydropower capacity, on the potential to comply with instant energy demand. To evaluate the impact, we developed two new metrics, power market impact and system efficiency ratio, which are based on two threshold flow regimes derived from natural flow as lower threshold release and regulated flow (based on hourly energy prices) as upper threshold release. The operation support model comprises 96 different regulation scenarios based on varying combinations of hydropower and reservoir capacities. For each scenario, an hourly water balance was simulated, to obtain the highest complying with upper threshold release based on actual energy demand. We tested the framework on the Kemijoki river with defined thresholds based on the natural flow regime (tributary river Ounasjoki) and the hourly energy price in Finland in 2017, and estimated the impact of regulation on hourly flow regime at the Taivalkoski hydropower station. The annual flow regime impact in 2013, 2014 and 2015 was estimated to be 74%, 84% and 61%, respectively, while the monthly impact varied from 27% to 100%. Our framework for evaluating interactions between the power market and sub-daily regulation practices is a useful novel tool for sustainable river management and can be easily applied to different rivers and regions and evaluated for different timescales.

  • 38.
    Vigouroux, Guillaume
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Destouni, G.
    Stockholm Univ, Dept Phys Geog, S-10691 Stockholm, Sweden..
    Jonsson, A.
    COWI AB, Solna Strandvag 78, S-78 Solna, Sweden..
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure. Royal Inst Technol KTH, Resources Energy & Infrastruct Sustainabil Assess, Teknikringen 10B, S-10044 Stockholm, Sweden..
    A scalable dynamic characterisation approach for water quality management in semi-enclosed seas and archipelagos2019In: Marine Pollution Bulletin, ISSN 0025-326X, E-ISSN 1879-3363, Vol. 139, p. 311-327Article in journal (Refereed)
    Abstract [en]

    In semi-enclosed seas, eutrophication may affect both the coastal waters and the whole sea. We develop and test a modelling approach that can account for nutrient loads from land as well as for influences and feedbacks on water quality across the scales of a whole semi-enclosed sea and its coastal zones. We test its applicability in the example cases of the Baltic Sea and one of its local archipelagos, the Archipelago Sea. For the Baltic Sea scale, model validation shows good representation of surface water quality dynamics and a generally moderate model performance for deeper waters. For the Archipelago Sea, management scenario simulations show that successful sea measures may have the most important effects on coastal water quality. This highlights the need to consistently account for whole-sea water-quality dynamics and management effects, in addition to effects of land drivers, in modelling for characterisation and management of local water quality.

  • 39.
    Wei, Jieqiang
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Nekouei, Ehsan
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Wu, J.
    Cvetkovic, Vladimir D.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Johansson, Karl H.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Steady-state analysis of a human-social behavior model: A neural-cognition perspective2019In: Proceedings of the American Control Conference, Institute of Electrical and Electronics Engineers (IEEE), 2019, p. 199-204, article id 8814786Conference paper (Refereed)
    Abstract [en]

    We consider an extension of the Rescorla-Wagner model which bridges the gap between conditioning and learning on a neural-cognitive, individual psychological level, and the social population level. In this model, the interaction among individuals is captured by a Markov process. The resulting human-social behavior model is a recurrent iterated function system which behaves differently from the classical Rescorla-Wagner model due to randomness. A sufficient condition for the convergence of the forward process starting with arbitrary initial distribution is provided. Furthermore, the ergodicity properties of the internal states of agents in the proposed model are studied.

  • 40.
    Wei, Jieqiang
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Wu, Junfeng
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Molinari, Marco
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On the modeling of neural cognition for social network applications2017In: 2017 IEEE Conference on Control Technology and Applications (CCTA), Institute of Electrical and Electronics Engineers (IEEE), 2017Conference paper (Refereed)
    Abstract [en]

    In this paper, we study neural cognition in social network. A stochastic model is introduced and shown to incorporate two well-known models in Pavlovian conditioning and social networks as special case, namely Rescorla-Wagner model and Friedkin-Johnsen model. The interpretation and comparison of these model are discussed. We consider two cases when the disturbance is independent identically distributed for all time and when the distribution of the random variable evolves according to a Markov chain. We show that the systems for both cases are mean square stable and the expectation of the states converges to consensus.

  • 41.
    Wörman, Anders
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Mojarrad, Babak Brian
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Riml, Joakim
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Fragmentation of the Hyporheic Zone Due to Regional Groundwater Circulation2019In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 55, no 2, p. 1-21Article in journal (Refereed)
    Abstract [en]

    By use of numerical modeling and field observations, this work quantified the effects of catchment-scale upwelling groundwater on the hyporheic (below stream) fluxes over a wide range of spatial scales. A groundwater flow model was developed that specifically accounted for the hydrostatic and dynamic head fluctuations induced by the streambed topography. Although the magnitudes and relative importance of these streambed-induced fluxes were found to be highly sensitive to site-specific hydromorphological properties, we showed that streambed topographic structures exert a predominant control on the magnitude of hyporheic exchange fluxes in a Swedish boreal catchment. The magnitude of the exchange intensity evaluated at the streambed interface was found to be dominated by the streambed-induced hydraulic head across stream order. However, the catchment-scale groundwater flow field substantially affected the distribution of groundwater discharge points and thus decreased the fragmentation of the hyporheic zone, specifically by shifting the cumulative density function toward larger areas of coherent upwelling at the streambed interface. This work highlights the spectrum of spatial scales affecting the surface water-groundwater exchange patterns and resolves the roles of key mechanisms in controlling the fragmentation of the hyporheic zone.

  • 42. Xie, Q.
    et al.
    Yang, James
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Lundström, S.
    Dai, W.
    Understanding morphodynamic changes of a tidal river confluence through field measurements and numerical modeling2018In: Water, ISSN 2073-4441, E-ISSN 2073-4441, Vol. 10, no 10, article id 1424Article in journal (Refereed)
    Abstract [en]

    A confluence is a natural component in river and channel networks. This study deals, through field and numerical studies, with alluvial behaviors of a confluence affected by both river run-offand strong tides. Field measurements were conducted along the rivers including the confluence. Field data show that the changes in flow velocity and sediment concentration are not always in phase with each other. The concentration shows a general trend of decrease from the river mouth to the confluence. For a given location, the tides affect both the sediment concentration and transport. A two-dimensional hydrodynamic model of suspended load was set up to illustrate the combined effects of run-offand tidal flows. Modeled cases included the flood and ebb tides in a wet season. Typical features examined included tidal flow fields, bed shear stress, and scour evolution in the confluence. The confluence migration pattern of scour is dependent on the interaction between the river currents and tidal flows. The flood tides are attributable to the suspended load deposition in the confluence, while the ebb tides in combination with run-offs lead to erosion. The flood tides play a dominant role in the morphodynamic changes of the confluence.

  • 43.
    Xie, Qiancheng
    et al.
    Lulea Univ Technol, Div Fluid & Expt Mech, S-97187 Lulea, Sweden..
    Yang, James
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Lundström, T. Staffan
    Lulea Univ Technol, Div Fluid & Expt Mech, S-97187 Lulea, Sweden..
    Field Studies and 3D Modelling of Morphodynamics in a Meandering River Reach Dominated by Tides and Suspended Load2019In: FLUIDS, ISSN 2311-5521, Vol. 4, no 1, article id 15Article in journal (Refereed)
    Abstract [en]

    Meandering is a common feature in natural alluvial streams. This study deals with alluvial behaviors of a meander reach subjected to both fresh-water flow and strong tides from the coast. Field measurements are carried out to obtain flow and sediment data. Approximately 95% of the sediment in the river is suspended load of silt and clay. The results indicate that, due to the tidal currents, the flow velocity and sediment concentration are always out of phase with each other. The cross-sectional asymmetry and bi-directional flow result in higher sediment concentration along inner banks than along outer banks of the main stream. For a given location, the near-bed concentration is 2-5 times the surface value. Based on Froude number, a sediment carrying capacity formula is derived for the flood and ebb tides. The tidal flow stirs the sediment and modifies its concentration and transport. A 3D hydrodynamic model of flow and suspended sediment transport is established to compute the flow patterns and morphology changes. Cross-sectional currents, bed shear stress and erosion-deposition patterns are discussed. The flow in cross-section exhibits significant stratification and even an opposite flow direction during the tidal rise and fall; the vertical velocity profile deviates from the logarithmic distribution. During the flow reversal between flood and ebb tides, sediment deposits, which is affected by slack-water durations. The bed deformation is dependent on the meander asymmetry and the interaction between the fresh water flow and tides. The flood tides are attributable to the deposition, while the ebb tides, together with run-offs, lead to slight erosion. The flood tides play a key role in the morphodynamic changes of the meander reach.

  • 44.
    Yang, James
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure. Vattenfall AB Res & Dev, Alvkarleby Lab, SE-81426 Alvkarleby, Sweden.
    Andreasson, Patrik
    Vattenfall AB Res & Dev, Alvkarleby Lab, SE-81426 Alvkarleby, Sweden.;Lulea Univ Technol, Div Fluid & Expt Mech, SE-97187 Lulea, Sweden..
    Högström, Carl-Maikel
    Vattenfall AB Res & Dev, Alvkarleby Lab, SE-81426 Alvkarleby, Sweden..
    Teng, Penghua
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    The Tale of an Intake Vortex and Its Mitigation Countermeasure: A Case Study from Akkats Hydropower Station2018In: Water, ISSN 2073-4441, E-ISSN 2073-4441, Vol. 10, no 7, article id 881Article in journal (Refereed)
    Abstract [en]

    The upgrade of Akkats power station in Sweden included a new, separate waterway for the addition of a 75 MW generating unit. The vertical intake of its headrace was formed by means of lake tapping. A physical model was used to help understand the blasting process involving fragmented rock, water, air, and gas. Upon commissioning of the unit, swirling flows occurred unexpectedly at the intake, which gave rise to negative consequences including limitations in power output. Echo-sounding showed that the blasted piercing resulted in an irregular intake. A hydraulic model, as part of the design process, was built to examine potential countermeasures for vortex suppression. The final solution was a segmented barrier between the intake and the dam. It effectively suppressed the intake flow circulations; only minor intermittent vortices were left. The fabricated steel segments were anchored into the bedrock, stretching to 1.0 m below the lowest legal reservoir level. The local intake headloss was also reduced. The implemented solution was tested under full turbine loading and the result was satisfactory. Even during winter seasons with ice cover above the wall, the power station ran normally. The case study is expected to provide guidance for solving similar problems with vortex formation.

  • 45.
    Yang, James
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Andreasson, Patrik
    Teng, Penghua
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Xie, Qiancheng
    The Past and Present of Discharge Capacity Modeling for Spillways-A Swedish Perspective2019In: FLUIDS, ISSN 2311-5521, Vol. 4, no 1, article id 10Article, review/survey (Refereed)
    Abstract [en]

    Most of the hydropower dams in Sweden were built before 1980. The present dam-safety guidelines have resulted in higher design floods than their spillway discharge capacity and the need for structural upgrades. This has led to renewed laboratory model tests. For some dams, even computational fluid dynamics (CFD) simulations are performed. This provides the possibility to compare the spillway discharge data between the model tests performed a few decades apart. The paper presents the hydropower development, the needs for the ongoing dam rehabilitations and the history of physical hydraulic modeling in Sweden. More than 20 spillways, both surface and bottom types, are analyzed to evaluate their discharge modeling accuracy. The past and present model tests are compared with each other and with the CFD results if available. Discrepancies do exist in the discharges between the model tests made a few decades apart. The differences fall within the range -8.3%-+11.2%. The reasons for the discrepancies are sought from several aspects. The primary source of the errors is seemingly the model construction quality and flow measurement method. The machine milling technique and 3D printing reduce the source of construction errors and improve the model quality. Results of the CFD simulations differ, at the maximum, by 3.8% from the physical tests. They are conducted without knowledge of the physical model results in advance. Following the best practice guidelines, CFD should generate results of decent accuracy for discharge prediction.

  • 46.
    Yang, James
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Lin, C.
    Kao, M. -J
    Teng, Penghua
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Raikar, R. V.
    Application of SIM, HSPIV, BTM, and BIV techniques for evaluations of a two-phase air-water chute aerator flow2018In: Water, ISSN 2073-4441, E-ISSN 2073-4441, Vol. 10, no 11, article id 1590Article in journal (Refereed)
    Abstract [en]

    Four image-based techniques-i.e., shadowgraphic image method (SIM), high-speed particle image velocimetry (HSPIV), bubble tracking method (BTM), and bubble image velocimetry (BIV)-are employed to investigate an aerator flow on a chute with a 17° inclination angle. The study focuses on their applications to the following issues: (1) to explore the characteristic positions of three water-air interfaces; (2) to interpret the evolution process of air bubbles shed from the wedged tip of the air cavity; (3) to identify the probabilistic means for characteristic positions near the fluctuating free surface; (4) to explore the probability distribution of intermittent appearance of air bubbles in the flow; (5) to obtain the mean streamwise and transverse velocity distributions of the water stream; (6) to acquire velocity fields, both instantaneous and mean, of air bubbles; (7) to construct a two-phase mean velocity field of both water flow and air-bubbles; and (8) to correlate the relationship among the probability distribution of air bubbles, the mean streamwise and transverse velocity profiles of air bubbles, and water stream. The combination of these techniques contributes to a better understanding of two-phase flow characteristics of the chute aerator.

  • 47.
    Yang, James
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Teng, Penghua
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Lin, Chang
    Air-vent layouts and water-air flow behaviors of a wide spillway aerator2019In: Theoretical and Applied Mechanics Letters, ISSN 2095-0349, Vol. 9, no 2, p. 130-143Article in journal (Refereed)
    Abstract [en]

    A spillway aerator should guarantee favorable flow conditions in the coupled water-air system even if the aerator is unconventionally wide. Eight air-vent configurations are devised and incorporated into a 35-m wide chute aerator for a generalized study. Computational fluid dynamics (CFD) simulations are performed to explore their effects on water-jet and air-cavity features. The Re-normalisation group (RNG) k - epsilon turbulence model and the two-fluid model are combined to predict the two-phase flow field. The results demonstrate appreciable influences of the vent layouts on the water-air flow. The air vents stir the air motion and re-distribute the cavity air pressure. Once the vent layout is modified, reciprocal adjustments exist between the jet behavior and air-pressure field in the cavity, thus leading to considerable differences in air-flow rate, jet-trajectory length, vent air-flow distribution across the chute, etc. The large width plays a discernable role in affecting the aerated flow. Telling differences exist between the near-wall region and the central part of the chute. To improve the duct pressure propagation, a gradual augment of the vent area should be assigned towards the chute center. Relative to single-slot vents across the flow, the layouts with segregated vents gain by comparison. A designer should see to it that a vented aerator operates satisfactorily for a given range of flow discharges.

  • 48.
    Yang, James
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure. Vattenfall AB, R&D Älvkarleby Lab, Älvkarleby, Sweden.
    Teng, Penghua
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Zhang, Hongwei
    Inst Water Resources & Hydropower Res IWHR, Dept Hydraul, Beijing, Peoples R China..
    Experiments and CFD modeling of high-velocity two-phase flows in a large chute aerator facility2019In: Engineering Applications of Computational Fluid Mechanics, ISSN 1994-2060, E-ISSN 1997-003X, Vol. 13, no 1, p. 48-66Article, review/survey (Refereed)
    Abstract [en]

    Mathematical formulations of two-phase flows at an aerator remain a challenging issue for spillway design. Due to their complexities in terms of water-air interactions subjected to high flow velocities, experiments play an essential role in evaluations of numerical models. The paper focuses on the underlying influence of the air-water momentum exchange in the two-phase Two-Fluid Model. It is modified to better represent the drag force acting on a group of air bubbles and the wall lubrication force accounting for near-wall phase interactions. Based on data from a large aerator rig with an approach velocity of 14.3 m/s, the models are evaluated for calculations of entrained air characteristics of a flow mixture. The air bubble diameter used in the modeling ranges from 0.5 to 4 mm as suggested by the experiments. In terms of air cavity configurations and aerator air demand, smaller air bubbles lead to better agreement with the test results. As far as air concentrations are concerned, the modified model gains by comparison. In the air cavity zone, smaller bubble sizes also provide better matches with the experiments. However, the near-base air concentration remains overestimated downstream from the impact area. The fact that the program user must pre-define a single air bubble size in simulations presumably limits the correct reproduction of near-base air concentrations and of their decay.

  • 49.
    Zech, Alraune
    et al.
    UFZ Helmholtz Ctr Environm Res, Permoserstr 15, D-04318 Leipzig, Germany..
    Attinger, Sabine
    UFZ Helmholtz Ctr Environm Res, Permoserstr 15, D-04318 Leipzig, Germany.;Univ Potsdam, Inst Earth & Environm Sci, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany..
    Bellin, Alberto
    Univ Trento, Dept Civil Environm & Mech Engn, Via Mesiano 77, I-38123 Trento, Italy..
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Dietrich, Peter
    UFZ Helmholtz Ctr Environm Res, Permoserstr 15, D-04318 Leipzig, Germany.;Univ Tubingen, Ctr Appl Geosci, Holderlinstr 12, D-72074 Tubingen, Germany..
    Fiori, Aldo
    Roma Tre Univ, Dept Engn, Via Volterra 62, I-00146 Rome, Italy..
    Teutsch, Georg
    UFZ Helmholtz Ctr Environm Res, Permoserstr 15, D-04318 Leipzig, Germany..
    Dagan, Gedeon
    Tel Aviv Univ, Sch Mech Engn, IL-69978 Ramat Aviv, Israel..
    A Critical Analysis of Transverse Dispersivity Field Data2019In: Ground Water, ISSN 0017-467X, E-ISSN 1745-6584, Vol. 57, no 4, p. 632-639Article in journal (Refereed)
    Abstract [en]

    Transverse dispersion, or tracer spreading orthogonal to the mean flow direction, which is relevant e.g, for quantifying bio-degradation of contaminant plumes or mixing of reactive solutes, has been studied in the literature less than the longitudinal one. Inferring transverse dispersion coefficients from field experiments is a difficult and error-prone task, requiring a spatial resolution of solute plumes which is not easily achievable in applications. In absence of field data, it is a questionable common practice to set transverse dispersivities as a fraction of the longitudinal one, with the ratio 1/10 being the most prevalent. We collected estimates of field-scale transverse dispersivities from existing publications and explored possible scale relationships as guidance criteria for applications. Our investigation showed that a large number of estimates available in the literature are of low reliability and should be discarded from further analysis. The remaining reliable estimates are formation-specific, span three orders of magnitude and do not show any clear scale-dependence on the plume traveled distance. The ratios with the longitudinal dispersivity are also site specific and vary widely. The reliability of transverse dispersivities depends significantly on the type of field experiment and method of data analysis. In applications where transverse dispersion plays a significant role, inference of transverse dispersivities should be part of site characterization with the transverse dispersivity estimated as an independent parameter rather than related heuristically to longitudinal dispersivity.

  • 50.
    Zou, Liangchao
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Ivars, Diego Mas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Impact of Normal Stress Caused Closure on Fluid Flow and Solute Retention in Rock Fractures2018Conference paper (Refereed)
    Abstract [en]

    Modeling of coupled hydro-mechanical and chemical (HMC) processes in fractured rocks is an important topic for many geoengineering projects.  Over the past decades, many efforts have been devoted to study the flow and transport in single fractures with consideration of mechanical effects. It is generally known that the mechanical effects, i.e. normal and shear deformation, significantly affect fluid flow and solute transport processes in rough-walled rock fractures since the deformation may largely alter the structure of fracture apertures that directly controls transmissivity. Due to complicated physical processes combined with complexity of geometry structures, many issues remain open questions, such as fracture surface roughness characterization, deformation dependence of transmissivity and advective transport in natural rock fractures. In this work, we attempt to investigate the impact of stress caused closure on fluid flow and solute advective transport in a rough-walled fracture through numerical modeling.  A rough-walled fracture model is created based on a laser-scanned rock surface. The Bandis’s model is used to describe the fracture closure subject to normal stress. The flow is modeled by solving Reynolds equation and the advective transport is simulated through Lagrangian particle tracking. The results show that the normal stress caused fracture closure creates asperity contacts and reduces the mean aperture, which significantly reduces transmissivity, and affects the travel time and transport resistance. With increases of normal stress, the specific surface area reduces nonlinearly due to the nonlinear closure. In practice, especially for important hydrogeological projects, e.g. nuclear waste disposal, it is important to consider the coupled HMC processes in design and risk assessment.

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