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Numerical simulation of jet flow using LES
Louda, Petr ; Kozel, K. ; Příhoda, Jaromír
The work deals with the numerical method for the large eddy simulation (LES) of incompressible flow. Governing system of filtered Navier-Stokes equations is completed by the Smagorinsky turbulence model and the Poisson equation is used for pressure instead of the continuity equation. The numerical method is based on an explicit scheme with fourth order accurate central approximation for convection and resolved diffusion. Preliminary results for the plane turbulent free jet are shown. Problem of the prescription of boundary conditions is discussed in detail.
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Solving of Schrodinger's equation by finite element method
Höschl, Cyril
Numerical solution of electronic structures can be obtained using finite element method. Starting with a variational principle, the author derives the matrix form of discretized Schrodinger equation. Two examples demonstrate the correctness of the derived formula. Possible difficulties in solving real problems are shortly discussed.
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Influence of the T-stress on Plastic zone shape and size for different form of specimens
Seitl, Stanislav
In framework of two-parameter fracture mechanics the shape and size of the plastic zone at the tip of a crack were studied. Analytical estimate of the size and shape of the plastic zone was made by substituting Mises yield criterion. For three different specimens (namely CCT-center cracked plate tension specimen, CT-compact tension specimen and 3PB-single edge cracked three point bending specimen) the numerical solution is calculated by using ANSYS. Numerical results are presented to show the influences of the T-stress on the plastic zone. Both solutions are compared and the effect of constraint on the plastic zone was discussed
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Numerická simulace a vizualizace vytváření syntetizovaného proudu
Trávníček, Zdeněk ; Vogel, Jiří ; Vít, T.
The paper presents the results of numerical and experimental investigations of a synthetic jet generation. The experiments were performed in air by means of flow visualization and hot-wire anemometry. The subsequent numerical simulation was performed using the commercial code FLUENT. The geometry, boundary conditions, and material properties of the numerical simulation were defined according to the real experimental situation.
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Modelling of flow over a backward-facing step in streams with various turbulence level
Příhoda, Jaromír ; Sedlář, M.
Turbulent flow over a backward-facing step in streams with a various turbulence level was numerically simulated using software ANSYS CFX-5. Numerical solution carried on with the two-equation SST model and/or with a k-omega based Reynolds stress model was compared with experimental data obtained for three different values of free-stream turbulence level. The predicted length of the recirculation region corresponds well with experimental data but the dependence of the ratio xr/h on free-stream turbulence level is smaller.
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Numerické řešení sdílení tepla v proudu dopadajícím na stěnu
Kozel, K. ; Louda, Petr ; Příhoda, Jaromír
The paper deals with the numerical solution of 3D impinging turbulent jet cooling a weakly heated wall. The solution was carried out using the SST model and/or an explicit algebraic Reynolds stress model and completed by a generalized gradient-diffusion hypothesis for modelling of turbulent heat flux. While the EARSM model gives good results for the velocity field, all used models overestimate heat transfer in the impingement region.
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Numerické modelování složitých turbulentních proudění
Kozel, K. ; Louda, Petr ; Příhoda, Jaromír
The work deals with the numerical solution of turbulent impinging jet and round jet in a cross flow. The mathematical model is based on averaged Navier-Stokes equations closed by a turbulence model. Turbulence models used are a low-Reynolds-number eddy-viscosity model and/or an explicit algebraic Reynolds stress model. Numerical results are compared with experimental data. In case of impinging jet flow, the heat transfer is also solved.
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