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Prediction of flow over a backward-facing step in the Star CD code using various turbulence models
Štěpaníková, D. ; Příhoda, Jaromír
The comparison of several turbulence models was carried out by the commercial software Star CD for turbulent flow over a backward-facing step with the aim to assess their ability to accurately predict separated flow. Presented simulation was focused on the two aspects, namely the effect of the inlet boundary conditions on the prediction and the relaxation of the shear layer behind the reattachment. Used modifications of two-equation models, especially the non-linear k-eps model and the v2-f model, show some advantages in comparison with the standard k-eps model, but none of used modifications gives positively a better agreement with experimental data than the SST model.
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Proudění v okolí Ahmedova tělesa
Uruba, Václav ; Sedlák, K.
Flow in wake of a car model was studied experimentally in a wind channel. The model was designed on the basis of so called Ahmed body in ratio 3 : 20, width of the model was from wall to wall, no gap, prismatic shape. We concentrated out our attention on upper rear part of the model, separation of the boundary layer from roof and formation of the wake. The upper part of the wake forming a free shear layer was studied in detail. Two variants of the model with slant angles = 25° and 35° was examined respectively. Angle 25° shows more or less attached flow, while angle 35° generates fully detached flow from the ramp.
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Dual-time stepping method applied to a numerical solution of unsteady incompressible flow with a vibrating profile
Honzátko, R. ; Horáček, Jaromír ; Kozel, K.
The paper presents numerical solution of two-dimensional incompressible flow in the interaction with a vibrating profile. The profile has two degrees of freedom. Mathematical model is represented either by the Euler equations in the case of inviscid flow or the Navier-Stokes equations in the case of viscous flow. Finite volume method is used as a discretization method. The dual-time stepping method is applied to unsteady simulations. This method provides a possibility to develop a time-accurate time-marching scheme for unsteady incompressible flows. Computational domain deformation due to the profile motion are treated using the Arbitrary Lagrangian-Eulerian method (ALE). Numerical schemes used for unsteady flow calculations are implemented in a form satisfying the geometric conservation law (GCL).
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Jet Bouncing from Weaving Reed
Tesař, Václav
Subject of this contribution is a little known and seemingly impossible mechanism of the jet “reflecting” or“bouncing back” from an impact on a solid wall. This, of course, cannot occur if the wall were impermeable — the trick is to provide the wall with perforations that allow a part of the jetto pass through. On doing so this part has to change its direction and this has to be compensated by the remaining partchanging its direction too, to the opposite side from the jet axis. This part forms the “reflected” jet. Thephenomenon, which has applications in shuttle-less looms, was investigated by flow visualisation and a detailed flowfield computations.
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