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Analysis of the flow of a bimodal suspension at the pipe wall
Chára, Zdeněk ; Matoušek, Václav ; Novotný, Jakub ; Konfršt, Jiří
In the paper, the attention is focused on the flow of bimodal suspensions, where the coarse fraction is combined with the fine fraction with the resulting effect of reducing the total pressure losses. Using the PIV and PTV methods, the flow at the bottom of the pipe is analyzed. Using this approach, the velocities of both the bimodal mixture and the individual particle velocities of the coarse fraction were obtained. The velocities of the coarse particles were higher than the velocities of the fine fraction.
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Numerical simulations of flow over stationary deposit
Chára, Zdeněk ; Vlasák, Pavel ; Kysela, Bohuš ; Konfršt, Jiří
The paper deals with a water flow in a horizontal, circular pipe of inner diameter 40 mm with a stationary deposit. The deposit was formed by spheres of diameter d=6 mm. The thickness of the deposit was about two sphere diameters. The flow was experimentally studied by the PIV method and COMSOL Multiphysics 4.4 was used as tool for numerical simulations as well. Two approaches were used to create the stationary deposit. In the first one was the deposit was replaced by a rough wall with different values of the roughness parameter ks. In the second case the deposit was created from the identical spherical particles. The results of the simulations and the experimental data are compared.
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Numerical modelling of backward-facing step flow
Chára, Zdeněk ; Hoření, Bohumír
The contribution deals with a 3D numerical simulation of backward-facing step flow. The ratio of width to height of the channel before the expansion is 10:1, the height of the step is equal to the upstream channel height (expansion ratio is 2). Both the turbulent and the laminar flow regimes are simulated. The results will be used as a basis for experimental research, which will be focused on a mutual comparison of experimental methods – mainly LDA and PIV.
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