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Publications (10 of 26) Show all publications
Söderberg, D., Hedhammar, M., Mittal, N., Jansson, R., Widhe, M., Benselfelt, T., . . . Lundell, F. (2019). Bioactive composites of cellulose nanofibrils and recombinant silk proteins. Paper presented at National Meeting of the American-Chemical-Society (ACS), MAR 31-APR 04, 2019, Orlando, FL. Abstracts of Papers of the American Chemical Society, 257
Open this publication in new window or tab >>Bioactive composites of cellulose nanofibrils and recombinant silk proteins
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2019 (English)In: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 257Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-257609 (URN)000478860502767 ()
Conference
National Meeting of the American-Chemical-Society (ACS), MAR 31-APR 04, 2019, Orlando, FL
Note

QC 20190918

Available from: 2019-09-18 Created: 2019-09-18 Last updated: 2019-09-18Bibliographically approved
Zade, S., Fornari, W., Lundell, F. & Brandt, L. (2019). Buoyant finite-size particles in turbulent duct flow. Physical Review Fluids (4), Article ID 024303.
Open this publication in new window or tab >>Buoyant finite-size particles in turbulent duct flow
2019 (English)In: Physical Review Fluids, E-ISSN 2469-990X, no 4, article id 024303Article in journal (Refereed) Published
Abstract [en]

Particle image velocimetry and particle tracking velocimetry have been employed to investigate the dynamics of finite-size spherical particles, slightly heavier than the carrier fluid, in a horizontal turbulent square duct flow. Interface resolved direct numerical simulations (DNSs) have also been performed with the immersed boundary method at the same experimental conditions, bulk Reynolds number Re2H=5600, duct height to particle-size ratio 2H/dp=14.5, particle volume fraction Φ=1%, and particle to fluid density ratio ρp/ρf=1.0035. Good agreement has been observed between experiments and simulations in terms of the overall pressure drop, concentration distribution, and turbulent statistics of the two phases. Additional experimental results considering two particle sizes 2H/dp=14.5 and 9 and multiple Φ=1%, 2%, 3%, 4%, and 5% are reported at the same Re2H. The pressure drop monotonically increases with the volume fraction, almost linearly and nearly independently of the particle size for the above parameters. However, despite the similar pressure drop, the microscopic picture in terms of fluid velocity statistics differs significantly with the particle size. This one-to-one comparison between simulations and experiments extends the validity of interface resolved DNS in complex turbulent multiphase flows and highlights the ability of experiments to investigate such flows in considerable detail, even in regions where the local volume fraction is relatively high.

National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-243895 (URN)10.1103/PhysRevFluids.4.024303 (DOI)000458160100003 ()2-s2.0-85062418601 (Scopus ID)
Note

QC 20190215

Available from: 2019-02-09 Created: 2019-02-09 Last updated: 2019-09-03Bibliographically approved
Brouzet, C., Mittal, N., Lundell, F. & Söderberg, D. (2019). Characterizing the Orientational and Network Dynamics of Polydisperse Nanofibers on the Nanoscale. Macromolecules, 52(6), 2286-2295
Open this publication in new window or tab >>Characterizing the Orientational and Network Dynamics of Polydisperse Nanofibers on the Nanoscale
2019 (English)In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 52, no 6, p. 2286-2295Article in journal (Refereed) Published
Abstract [en]

Polydisperse fiber networks are the basis of many natural and manufactured structures, ranging from high-performance biobased materials to components of living cells and tissues. The formation and behavior of such networks are given by fiber properties such as length and stiffness as well as the number density and fiber-fiber interactions. Studies of fiber network behavior, such as connectivity or rigidity thresholds, typically assume monodisperse fiber lengths and isotropic fiber orientation distributions, specifically for nano scale fibers, where the methods providing time-resolved measurements are limited. Using birefringence measurements in a microfluidic flow-focusing channel combined with a flow stop procedure, we here propose a methodology allowing investigations of length-dependent rotational dynamics of nanoscale polydisperse fiber suspensions, including the effects of initial nonisotropic orientation distributions. Transition from rotational mobility to rigidity at entanglement thresholds is specifically addressed for a number of nanocellulose suspensions, which are used as model nanofiber systems. The results show that the proposed method allows the characterization of the subtle interplay between Brownian diffusion and nanoparticle alignment on network dynamics.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-246216 (URN)10.1021/acs.macromol.8b02714 (DOI)000462950300007 ()2-s2.0-85062860050 (Scopus ID)
Note

QC 20190318. QC 20191031

Available from: 2019-03-17 Created: 2019-03-17 Last updated: 2019-10-31Bibliographically approved
Nechyporchuk, O., Hakansson, K. M. O., Gowda, K. V., Lundell, F., Hagstrom, B. & Kohnke, T. (2019). Continuous Assembly of Cellulose Nanofibrils and Nanocrystals into Strong Macrofibers through Microfluidic Spinning. ADVANCED MATERIALS TECHNOLOGIES, 4(2), Article ID 1800557.
Open this publication in new window or tab >>Continuous Assembly of Cellulose Nanofibrils and Nanocrystals into Strong Macrofibers through Microfluidic Spinning
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2019 (English)In: ADVANCED MATERIALS TECHNOLOGIES, ISSN 2365-709X, Vol. 4, no 2, article id 1800557Article in journal (Refereed) Published
Abstract [en]

Microfluidic fiber spinning is a promising technique for assembling cellulose nanomaterials into macroscopic fibers. However, its implementation requires upscalabe fabrication processes while maintaining high strength of the fibers, which could not be previously achieved. Herein, a continuous wet spinning process based on microfluidic flow focusing is developed to produce strong fibers from cellulose nanofibrils (CNFs) and nanocrystals (CNCs). Fibers with an average breaking tenacity as high as 29.5 cN tex(-1) and Young's modulus of 1146 cN tex(-1) are reported for the first time, produced from nonhighly purified CNF grades. Using the same developed method, wet spinning of fibers from CNCs is achieved for the first time, reaching an average Young's modulus of 1263 cN tex(-1) and a breaking tenacity of 10.6 cN tex(-1), thus exhibiting strength twice as high as that of common CNC films. A rather similar stiffness of CNC and CNF spun fibers may originate from similar degrees of alignment, as confirmed by wide-angle X-ray scattering (WAXS) and birefringence measurements, whereas lower strength may primarily arise from the shorter length of CNCs compared to that of CNFs. The benefit of CNCs is their higher solids content in the dopes. By combining both CNCs and CNFs, the fiber properties can be tuned.

Place, publisher, year, edition, pages
WILEY, 2019
Keywords
cellulose nanocrystals, cellulose nanofibrils, flow focusing, microfluidic fiber spinning, nanocellulose
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-246272 (URN)10.1002/admt.201800557 (DOI)000459632800051 ()2-s2.0-85058288929 (Scopus ID)
Note

QC 20190326

Available from: 2019-03-26 Created: 2019-03-26 Last updated: 2019-04-04Bibliographically approved
Yada, S., Bagheri, S., Hansson, J., Do-Quang, M., Lundell, F., van der Wijngaart, W. & Amberg, G. (2019). Droplet leaping governs microstructured surface wetting. Soft Matter
Open this publication in new window or tab >>Droplet leaping governs microstructured surface wetting
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2019 (English)In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848Article in journal (Refereed) Published
Keywords
droplet
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-263793 (URN)10.1039/C9SM01854A (DOI)
Note

QC 20191126

Available from: 2019-11-14 Created: 2019-11-14 Last updated: 2019-11-26Bibliographically approved
Gowda, K. V., Brouzet, C., Lefranc, T., Söderberg, D. & Lundell, F. (2019). Effective interfacial tension in flow-focusing of colloidal dispersions: 3-D numerical simulations and experiments. Journal of Fluid Mechanics, 876, 1052-1076, Article ID PII S0022112019005664.
Open this publication in new window or tab >>Effective interfacial tension in flow-focusing of colloidal dispersions: 3-D numerical simulations and experiments
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2019 (English)In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 876, p. 1052-1076, article id PII S0022112019005664Article in journal (Refereed) Published
Abstract [en]

An interface between two miscible fluids is transient, existing as a non-equilibrium state before complete molecular mixing is reached. However, during the existence of such an interface, which typically occurs at relatively short time scales, composition gradients at the boundary between the two liquids cause stresses effectively mimicking an interfacial tension. Here, we combine numerical modelling and experiments to study the influence of an effective interfacial tension between a colloidal fibre dispersion and its own solvent on the flow in a microfluidic system. In a flow-focusing channel, the dispersion is injected as core flow that is hydrodynamically focused by its solvent as sheath flows. This leads to the formation of a long fluid thread, which is characterized in three dimensions using optical coherence tomography and simulated using a volume of fluid method. The simulated flow and thread geometries very closely reproduce the experimental results in terms of thread topology and velocity flow fields. By varying the interfacial tension numerically, we show that it controls the thread development, which can be described by an effective capillary number. Furthermore, we demonstrate that the applied methodology provide the means to measure the ultra-low but dynamically highly significant effective interfacial tension.

Place, publisher, year, edition, pages
CAMBRIDGE UNIV PRESS, 2019
Keywords
colloids, capillary flows, multiphase flow
National Category
Fluid Mechanics and Acoustics
Research subject
Physics, Material and Nano Physics
Identifiers
urn:nbn:se:kth:diva-261291 (URN)10.1017/jfm.2019.566 (DOI)000486462700001 ()2-s2.0-85070832669 (Scopus ID)
Note

QC 20191008

Available from: 2019-10-08 Created: 2019-10-08 Last updated: 2019-11-26Bibliographically approved
Vijayakumar, K., Söderberg, D. & Lundell, F. (2019). Orientation and alignment of cellulose nanofibrils in shear and extensional flows. Paper presented at National Meeting of the American-Chemical-Society (ACS), MAR 31-APR 04, 2019, Orlando, FL. Abstracts of Papers of the American Chemical Society, 257
Open this publication in new window or tab >>Orientation and alignment of cellulose nanofibrils in shear and extensional flows
2019 (English)In: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 257Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-257593 (URN)000478860503039 ()
Conference
National Meeting of the American-Chemical-Society (ACS), MAR 31-APR 04, 2019, Orlando, FL
Note

QC 20190919

Available from: 2019-09-19 Created: 2019-09-19 Last updated: 2019-09-19Bibliographically approved
Zade, S., Lundell, F. & Brandt, L. (2019). Turbulence modulation by finite-size spherical particles in Newtonian and viscoelastic fluids. International Journal of Multiphase Flow, 112, 116-129
Open this publication in new window or tab >>Turbulence modulation by finite-size spherical particles in Newtonian and viscoelastic fluids
2019 (English)In: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, Vol. 112, p. 116-129Article in journal (Refereed) Published
Abstract [en]

We experimentally investigate the influence of finite-size spherical particles in turbulent flows of a Newtonian and a drag reducing viscoelastic fluid at varying particle volume fractions and fixed Reynolds number. Experiments are performed in a square duct at a Reynolds number Re2H of nearly 1.1 × 104, Weissenberg number Wi for single phase flow is between 1 and 2 and results in a drag-reduction of 43% compared to a Newtonian flow (at the same Re2H). Particles are almost neutrally-buoyant hydrogel spheres having a density ratio of 1.0035 ± 0.0003 and a duct height 2H to particle diameter dp ratio of around 10. We measure flow statistics for four different volume fractions ϕ namely 5, 10, 15 and 20% by using refractive-index-matched Particle Image Velocimetry (PIV). For both Newtonian Fluid (NF) and Visceolastic Fluid (VEF), the drag monotonically increases with ϕ. For NF, the magnitude of drag increase due to particle addition can be reasonably estimated using a concentration dependent effective viscosity for volume fractions below 10%. The drag increase is, however, underestimated at higher ϕ. For VEF, the absolute value of drag is lower than NF but, its rate of increase with ϕ is higher. Similar to particles in a NF, particles in VEF tend to migrate towards the center of the duct and form a layer of high concentration at the wall. Interestingly, relatively higher migration towards the center and lower migration towards the walls is observed for VEF. The primary Reynolds shear stress reduces with increasing ϕ throughout the duct height for both types of fluid.

Place, publisher, year, edition, pages
Elsevier, 2019
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-243840 (URN)10.1016/j.ijmultiphaseflow.2018.12.015 (DOI)2-s2.0-85058816573 (Scopus ID)
Note

QC 20190215

Available from: 2019-02-07 Created: 2019-02-07 Last updated: 2019-09-03Bibliographically approved
Shahmardi, A., Zade, S., Niazi Ardekani, M., Poole, R. J., Lundell, F., Rosti, M. E. & Brandt, L. (2019). Turbulent duct flow with polymers. Journal of Fluid Mechanics, 859, 1057-1083
Open this publication in new window or tab >>Turbulent duct flow with polymers
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2019 (English)In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 859, p. 1057-1083Article in journal (Refereed) Published
Abstract [en]

We have performed direct numerical simulation of the turbulent flow of a polymer solution in a square duct, with the FENE-P model used to simulate the presence of polymers. First, a simulation at a fixed moderate Reynolds number is performed and its results compared with those of a Newtonian fluid to understand the mechanism of drag reduction and how the secondary motion, typical of the turbulent flow in non-axisymmetric ducts, is affected by polymer additives. Our study shows that the Prandtl's secondary flow is modified by the polymers: the circulation of the streamwise main vortices increases and the location of the maximum vorticity moves towards the centre of the duct. In-plane fluctuations are reduced while the streamwise ones are enhanced in the centre of the duct and dumped in the corners due to a substantial modification of the quasi-streamwise vortices and the associated near-wall low- and high-speed streaks; these grow in size and depart from the walls, their streamwise coherence increasing. Finally, we investigated the effect of the parameters defining the viscoelastic behaviour of the flow and found that the Weissenberg number strongly influences the flow, with the cross-stream vortical structures growing in size and the in-plane velocity fluctuations reducing for increasing flow elasticity.We have performed direct numerical simulation of the turbulent flow of a polymer solution in a square duct, with the FENE-P model used to simulate the presence of polymers. First, a simulation at a fixed moderate Reynolds number is performed and its results compared with those of a Newtonian fluid to understand the mechanism of drag reduction and how the secondary motion, typical of the turbulent flow in non-axisymmetric ducts, is affected by polymer additives. Our study shows that the Prandtl's secondary flow is modified by the polymers: the circulation of the streamwise main vortices increases and the location of the maximum vorticity moves towards the centre of the duct. In-plane fluctuations are reduced while the streamwise ones are enhanced in the centre of the duct and dumped in the corners due to a substantial modification of the quasi-streamwise vortices and the associated near-wall low- and high-speed streaks; these grow in size and depart from the walls, their streamwise coherence increasing. Finally, we investigated the effect of the parameters defining the viscoelastic behaviour of the flow and found that the Weissenberg number strongly influences the flow, with the cross-stream vortical structures growing in size and the in-plane velocity fluctuations reducing for increasing flow elasticity.

Place, publisher, year, edition, pages
Cambridge University Press, 2019
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-240129 (URN)10.1017/jfm.2018.858 (DOI)000451519800001 ()2-s2.0-85057589811 (Scopus ID)
Funder
Swedish Research Council, 2014-5001EU, European Research Council, ERC-2013-CoG-616186Swedish e‐Science Research Center
Note

QC 20181213

Available from: 2018-12-12 Created: 2018-12-12 Last updated: 2018-12-13Bibliographically approved
Zade, S., Costa, P., Fornari, W., Lundell, F. & Brandt, L. (2018). Experimental investigation of turbulent suspensions of spherical particles in a squareduct. Journal of Fluid Mechanics, 857, 748-783
Open this publication in new window or tab >>Experimental investigation of turbulent suspensions of spherical particles in a squareduct
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2018 (English)In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 857, p. 748-783Article in journal (Refereed) Published
Abstract [en]

We report experimental observations of turbulent flow with spherical particles in a square duct. Three particle sizes, namely 2H/d(p) = 40, 16 and 9 (2H being the duct full height and d(p) being the particle diameter), are investigated. The particles are nearly neutrally buoyant with a density ratio of 1.0035 and 1.01 with respect to the suspending fluid. Refractive index matched-particle image velocimetry (RIM-PIV) is used for fluid velocity measurement even at the highest particle volume fraction (20 %) and particle tracking velocimetry (PTV) for the particle velocity statistics for the flows seeded with particles of the two largest sizes, whereas only pressure measurements are reported for the smallest particles. Settling effects are seen at the lowest bulk Reynolds number R-e2H approximate to 10 000, whereas, at the highest R-e2H approximate to 27 000, particles are in almost full suspension. The friction factor of the suspensions is found to be significantly larger than that of single-phase duct flow at the lower R-e2H investigated; however, the difference decreases when increasing the flow rate and the total drag approaches the values of the single-phase flow at the higher Reynolds number considered, R-e2H = 27 000. The pressure drop is found to decrease with the particle diameter for volume fractions lower than (sic) = 10% for nearly all R-e2H investigated. However, at the highest volume fraction (sic) = 20 %, we report a peculiar non-monotonic behaviour: the pressure drop first decreases and then increases with increasing particle size. The decrease of the turbulent drag with particle size at the lowest volume fractions is related to an attenuation of the turbulence. The drag increase for the two largest particle sizes at (sic) = 20 %, however, occurs despite this large reduction of the turbulent stresses, and it is therefore due to significant particle-induced stresses. At the lowest Reynolds number, the particles reside mostly in the bottom half of the duct, where the mean velocity significantly decreases; the flow is similar to that in a moving porous bed near the bottom wall and to turbulent duct flow with low particle concentration near the top wall.

Place, publisher, year, edition, pages
CAMBRIDGE UNIV PRESS, 2018
Keywords
multiphase flow, particle/fluid flow, suspensions
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-239092 (URN)10.1017/jfm.2018.783 (DOI)000448523200001 ()
Funder
EU, European Research Council, ERC-2013-CoG-616186Swedish Research Council
Note

QC 20181121

Available from: 2018-11-21 Created: 2018-11-21 Last updated: 2019-09-03Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-2504-3969

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