Search

Your search keyword '"Lundström T"' showing total 804 results
Start Over Author "Lundström T"
804 results on '"Lundström T"'

2. Velocity distribution measurements in a fishway like open channel by Laser Doppler Anemometry (LDA)

Author

Sayeed-Bin-Asad S.M., Lundström T. S., Andersson A.G., and Hellström J. G. I.

Subjects
Physics, QC1-999
Abstract

Experiments in an open channel flume with placing a vertical half cylinder barrier have been performed in order to investigate how the upstream velocity profiles are affected by a barrier. An experimental technique using Laser Doppler Velocimetry (LDV) was adopted to measure these velocity distributions in the channel for four different discharge rates. Velocity profiles were measured very close to wall and at 25, 50 and 100 mm upstream of the cylinder wall. For comparing these profiles with well-known logarithmic velocity profiles, velocity profiles were also measured in smooth open channel flow for all same four discharge rates. The results indicate that regaining the logarithmic velocity profiles upstream of the half cylindrical barrier occurs at 100 mm upstream of the cylinder wall.

Published
2016
Full Text
View/download PDF

9. Effect of momentum flow ratio on entrainment of a confined coaxial jet in a co-flow.

Author

Östman, N. Martin, Larsson, I. A. Sofia, Lundström, T. Staffan, Marjavaara, Daniel, and Normann, Fredrik

Subjects
REYNOLDS stress, HYDROGEN flames, ROTARY kilns, FOSSIL fuels, MANUFACTURING processes
Abstract

Iron ore pellet production processes produce large amounts of CO2 emissions when burning fossil fuels. One example is the grate-kiln process, where normally a coal flame is used to indurate pellets. To mitigate the emissions, coal used in rotary kilns can be replaced with for example hydrogen. However, the fuel is mixed with secondary process air, and replacing a solid fuel with a gaseous one changes the mixing characteristics. This demands different means of injecting the fuel. A coaxial jet can be used to control the mixing of fuel and secondary air, as well as the flow field. The aim is to control the mixing of hydrogen and secondary air to achieve a hydrogen flame that is similar to the reference coal flame. This study numerically investigates different coaxial jet configurations. Steady-state simulations of a simplified model of the real kiln are performed using a Reynolds Stress turbulence model. Results show that decreasing the momentum flow ratio between the outer and inner jet, Mjet, to a certain value delays the spread of the hydrogen jet and thus gives a longer jet. Further decreasing this ratio gives an even longer jet, but has the side effect of producing recirculation of hydrogen. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

26. Experimental investigation of face mask filtration in the 15–150 μm range for stationary flows.

Author

Öhman, Johan, Gren, Per, Sjödahl, Mikael, and Lundström, T. Staffan

Subjects
MEDICAL masks, AIR flow, AIRBORNE infection, FILTERS & filtration, COVID-19 pandemic, WATER filtration
Abstract

The effectiveness of face masks for preventing airborne transmission has been debated heavily during the COVID-19 pandemic. This paper investigates the filtration efficiency for four different face mask materials, two professional and two homemade, for different airflow conditions using model experiments and artificially generated water droplets. The size range chosen represents particles with the largest volume that can be suspended in air. The particles are detected using double pulsed interferometric particle imaging, from which it is possible to estimate the positions, velocity, and size of individual particles. It is found that all the tested face masks are efficient in preventing particles from transmission through the mask material. In the presence of leakage, particles larger than approximately 100 μ m are completely removed from the air stream. The filtration efficiency decreases with the decreasing particle size to approximately 80 % for 15 μ m particles. The size dependency in the leakage is mainly due to the momentum of the larger particles. The results show that even simple face mask materials with leakage prevent a large portion of the emitted particles in the 15–150 μ m range. [ABSTRACT FROM AUTHOR]

Published
2022
Full Text
View/download PDF

28. A dual-lattice hydrodynamic-thermal MRT-LBM model implemented on GPU for DNS calculations of turbulent thermal flows

Author

Forslund, Tobias O. M., Larsson, I. A. Sofia, Hellström, J. Gunnar I., Lundström, T. Staffan, Forslund, Tobias O. M., Larsson, I. A. Sofia, Hellström, J. Gunnar I., and Lundström, T. Staffan

Abstract

Purpose The purpose of this paper is to present a fast and bare bones implementation of a numerical method for quickly simulating turbulent thermal flows on GPUs. The work also validates earlier research showing that the lattice Boltzmann method (LBM) method is suitable for complex thermal flows. Design/methodology/approach A dual lattice hydrodynamic (D3Q27) thermal (D3Q7) multiple-relaxation time LBM model capable of thermal DNS calculations is implemented in CUDA.FindingsThe model has the same computational performance compared to earlier publications of similar LBM solvers. The solver is validated against three benchmark cases for turbulent thermal flow with available data and is shown to be in excellent agreement. Originality/value The combination of a D3Q27 and D3Q7 stencil for a multiple relaxation time -LBM has, to the authors’ knowledge, not been used for simulations of thermal flows. The code is made available in a public repository under a free license., Validerad;2023;Nivå 2;2023-07-13 (sofila);This article has previously appeared as a manuscript in a thesis

Published
2023
Full Text
View/download PDF

29. Steady-State Transitions in Ordered Porous Media

Author

Forslund, Tobias O.M., Larsson, I. A. Sofia, Hellström, J. Gunnar I., Lundström, T. Staffan, Forslund, Tobias O.M., Larsson, I. A. Sofia, Hellström, J. Gunnar I., and Lundström, T. Staffan

Abstract

Previously performed experiments on flow through an ordered porous media cell with tomographic particle image velocimetry reveal a complex three-dimensional steady-state flow pattern. This flow pattern emerge in the region where inertial structures have been previously reported for a wide range of packings. The onset of these steady-state inertial flow structures is here scrutinized for three different types of packing using a finite difference method. It is concluded that the onset of the flow structure coincides with a symmetry break in the flow field and discontinuities in the pressure drop, volume averaged body forces and heat transfer. A quantity for identifying the transition is proposed, namely the pressure integral across the solid surfaces. It is also shown that the transition can both increase and decrease the heat transfer dependent on the actual geometry of the porous medium., Validerad;2023;Nivå 2;2023-08-15 (hanlid);This article has previously appeared as a manuscript in a thesis.Licens fulltext: CC BY License

Published
2023
Full Text
View/download PDF

30. Modeling Convective Heat Transfer of Air in a Data Center Using OpenFOAM : Evaluation of the Boussinesq Buoyancy Approximation

Author

Barestrand, Henrik A., Ljung, Anna-Lena, Summers, Jon, Lundström, T. Staffan, Barestrand, Henrik A., Ljung, Anna-Lena, Summers, Jon, and Lundström, T. Staffan

Abstract

Achieving energy and cooling efficiency in data center convective air flow and heat transfer can be a challenging task. Among different numerical methods to work with such issues is the Finite Volume Method in Computational Fluid Dynamics. This work evaluates the performance of two such solvers provided by OpenFOAM® in solving this type of convective heat-transfer problem, namely BuoyantBoussinesqPimpleFOAM and BuoyantPimpleFOAM. This is done for two different flow configurations of significantly different Richardson number. To sufficiently resolve the flow, grid sizing effects are elucidated by way of the kernel density estimate. It determines the volume distribution of the temperature in the data center configuration. For the k-epsilon turbulence model used here, it was found that the compressible solver performs faster and requires less grid resolution for both flow configurations. This is attributed to the nature of the boundary conditions which are set such that the mass flow conservation per server rack and cooling unit is achieved. Transient solutions are found to provide better iterative convergence for cases that involves buoyancy, compressibility and flow separation. This is, in comparison to steady-state solutions where artificial numerical pressure drop is found, to depend on the momentum relaxation factors for the convective case with a higher Richardson number., Godkänd;2023;Nivå 0;2023-08-09 (hanlid)

Published
2023
Full Text
View/download PDF

47. Randomized clinical trial of Appendicitis Inflammatory Response score‐based management of patients with suspected appendicitis

Author

Andersson, M., Kolodziej, B., Andersson, R. E., Andersson, R. E., Andersson, M., Eriksson, T., Ramsing, A., Westman, L., Björkman, J., Håkansson, H. O., Lundström, T., Björkman, H., Johansson, P., Hjert, O., Edin, R., Ekström, A., Wenander, C., Wallon, C., Andersson, P., Frisk, J., Arvidsson, B., Lantz, R., Wallin, G., Wickberg, Å., Stenberg, E., Erixon, C., Schmidt, W., Räntfors, J., Göthberg, G., Styrud, J., Elias, K., Boström, Le., Kretschmar, G., Jonsson, M., Brav, C., Nilsson, I., Kamran, F., Hammarqvist, F., Rutqvist, J., Almström, M., Hedberg, M., Lindh, V., Rosemar, A., Wangberg, H., Gustafsson, J., Neovius, G., Juhlin, C., Christofferson, R., Månsson, C., Zittel, T., and Fagerström, N.

Published
2017
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results