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Validace CFD výpočtů s experimentálními daty, metody a jejich přesnost
Uruba, Václav
Validation and verification are the processes which could the virtual reality of CFD simulations bring closer to physical reality. The key role in those processes play the method of quantification of similitude of the different situations in the flow-field, thus the metric, which should be properly chosen. In the verification process the proper strategy of the mathematical model modification should be adopted, while in the validation process the proper experimental data should be utilized. The experimental data is used also for the boundary condition definition. The present paper deals with those aspects.
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Physical modelling axisymmetric diffusors by plane models
Uruba, Václav
Diffusers with axisymmetric geometry are used very often in technical applications, they are characterized by circular cross-section along the flow axis. Such geometry is not suitable for application of optical methods, so the plane model with rectangular cross-section is used instead very often. However the flow inside such model could be significantly different as for velocity and pressure fields. The physical similarity of 1D flow in axisymmetric diffusers and plane models will be studied in details. The plane model opening angle is suggested to optimize velocity and pressure distributions in the model.
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Coanda effect in valves
Uruba, Václav ; Procházka, Pavel P. ; Skála, Vladislav
Coanda effect takes place in flow within valves diffuser for certain conditions. The valve plug in\nhalf-closed position forms wall-jet, which could be stable or instable, depending on geometry and other\nconditions. This phenomenon was subject of experimental study using time-resolved PIV technique. For the acquired data analysis the special spatio-temporal methods have been used.
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On stability of 2D flow-field
Uruba, Václav
Stability of a 2D flow-field generated under 2D boundary conditions will be analyzed using various methods. The most practical cases of such flows are found to be highly instable and thus unphysical. The presented paper analyses the situation with help of experiments and mathematical modelling from literature defining an interesting areas for future experimental research, which could extend the published experimental studies and/or verify some recent results of mathematical modelling.
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Force interaction of an airfoil in fluid flow
Uruba, Václav
The physical mechanism of lift and drag forces exerted on an airfoil is studied using results from mathematical modelling. Special attention is paid to lift force origin. The mechanism based on 3D flow-structure as a result of 2D flow-field instability is described.
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(An)Isotropy Analysis of Turbulence
Uruba, Václav
Basic ideas of (an)isotropy analysis and rating of turbulent flows are presented oriented on point velocity data analysis. Two types of anisotropy invariant maps are proposed. Practical example is shown.
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