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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.
    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.

  • 4.
    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.

  • 5.
    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)
  • 6.
    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.

  • 7.
    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

  • 8.
    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)
  • 9. 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%.

  • 10.
    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.

  • 11.
    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. 

  • 12.
    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.

  • 13.
    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.

  • 14.
    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.

  • 15.
    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.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Ivars, Diego Mas
    KTH.
    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.

  • 16.
    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.

  • 17.
    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.

  • 18.
    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. Vattenfall AB, R&D Älvkarleby Laboratory, SE-81426 Älvkarleby, Sweden .
    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.

  • 19.
    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.

  • 20.
    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.

  • 21.
    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 Alvkarleby Lab, Alvkarleby, 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.

  • 22.
    Zou, Liangchao
    et al.
    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.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Modeling of rock grouting in saturated variable aperture fractures2018In: Proceedings of Bergdagarna 2018., 2018, p. 79-87, article id 10Conference paper (Refereed)
    Abstract [en]

    Modeling and analysis of cement grouts flow in rock fractures is important in the design, execution and monitoring of grouting in fractured rocks. At present, modeling of rock grouting mainly relies on analytical models, e.g., the real time grouting control (RTGC) method. In the RTGC method, it is assumed that the rock fractures are consisting of smooth parallel plates or disks and water flow is neglected. However, in reality, the natural rock fractures are commonly consisting of complex rough-walled surfaces and are filled with groundwater; therefore, grouting is actually a multiphase (non-Newtonian grouts and groundwater) flow process in rough-walled rock fractures with variable apertures. In this study, we present an efficient one-dimensional (1D) numerical model for modeling of rock grouting in a single rock fracture with consideration of multiphase flow and variable apertures. It is assumed that the cement grouts are Bingham fluids and that the analytical solution for flowrate with a given pressure gradient in a pair of smooth parallel plates is locally applicable. A time-dependent advection equation is used to describe the interface (between the grout and groundwater) propagation. A finite element method (FEM) code is developed to iteratively solve the mass balance and the interface advection equations. The numerical simulations are compared with the RTGC method. It generally shows that water flow significantly affect grouts penetration in the fracture, especially for the grouts with relatively lower viscosity. The variable aperture significantly postpones the penetration process compared with that of constant aperture. This numerical model is able to describe more realistic physical processes and geometry conditions in rock grouting, which can be readily used in practice to reduce the potential uncertainties in application of simplified analytical models.

  • 23.
    Zou, Liangchao
    et al.
    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.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Two-phase cement grout propagation in homogeneous water-saturated rock fractures2018In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 106, p. 243-249Article in journal (Refereed)
    Abstract [en]

    Modeling of cement grout flow in rock fractures is important for the design, monitoring and execution of rock grouting that is widely used in a variety of rock engineering applications. This study presents a mathematical model based on the Reynolds flow equation for cement grout flow in a homogeneous water-saturated rock fracture. The model is based on two-phase flow, i.e. grout as a Bingham fluid and groundwater as a Newtonian fluid, and is used for investigating the importance of the water phase in rock grouting. The modeling results for the two-phase flow generally show the importance of the water phase that can significantly affect the pressure distribution and grout penetration in the fracture, especially under the condition of grout hardening. Such effects depend on the viscosity ratio between the grout and groundwater, which becomes increasingly important for cases with smaller values of the viscosity ratio. The grout density also affects the grout penetration length. Applying an analytical solution based on single-phase flow, i.e. neglecting the impact of groundwater flow, for modeling grout injection, will generally overestimate the penetration length.

  • 24.
    Zou, Liangchao
    et al.
    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, Land and Water Resources Engineering.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Effect of sorption on solute transport in a single rough rock fracture2017In: 13th ISRM International Congress of Rock Mechanics, International Society for Rock Mechanics , 2017Conference paper (Refereed)
    Abstract [en]

    Sorption process plays a significant role for solute retardation in rock fractures. In this paper, for the aim to investigate the effect of sorption on solute transport in a single rough fracture, a 2D model of representative single rock fracture was built and its roughness was statistically characterized based on the measured data of rock surface topography by laser scanning. A Finite Volume Method (FVM) code was developed to solve the Navier-Stokes (NS) equations and transport equation for numerical modelling the process of fluid flow and solute transport in the rock fracture model. Two groups of simulations were conducted: with and without the consideration of the sorption process with different average flow velocities. The results show that the surface roughness increased the complexities of flow fields, and the non-linear sorption process plays a significant role in the retardation of solute transport through rock fractures. The sorption process caused an obvious lagging time in both the solute concentration fields (plumes) and corresponding breakthrough curves. This lagging time increases with the distance from the inlet boundary, and relatively decreases with the increase of mean velocities.

  • 25.
    Zou, Liangchao
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Shear-enhanced nonlinear flow in rough-walled rock fractures2017In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 97, p. 33-45Article in journal (Refereed)
    Abstract [en]

    Nonlinear flow in 3D rough-walled rock fractures is simulated by solving the Navier-Stokes equations. The emphasis is on the impact of shear-caused aperture changes (variable apertures and asperity contacts) and flow conditions (inertial term) upon nonlinear flow behavior. In order to compare shear effects, two 3D fracture models, with and without shear, were established with identical initial rough-walled surfaces topographies of a realistic rock sample. Five groups of simulations with different inflow boundary conditions of flowrates/Reynolds numbers (Re) were conducted to demonstrate shear-enhanced nonlinearity of flow fields and limitations of local cubic law (LCL) approach. The flow results clearly show channeling flow along the preferential paths, transverse flow around the contact spots, and eddy flows behind contact spots with increasing Re, which cannot be observed in 2D models. The effective transmissivity of the 3D fracture model was calculated from the modeling results of velocity and pressure fields. The results showed that the effective transmissivity is a function of local apertures with important uncertainties even when Re is small (i.e. Re = 0.4 in this study), thus the validity of the transmissivity evaluation using LCL approach for nonlinear flow in 3D rough-walled rock fractures is questionable.

1 - 25 of 25
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