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On the validation study devoted to stratified atmospheric flow over an isolated hill
Sládek, Ivo ; Kozel, Karel ; Jaňour, Zbyněk
The paper deals with description of the validation model, °ow conditions and mainly it presents some numerical results. Reference and input data for the validation study are based on work of Eidsvik [3]. The mathematical model is based on the system of RANS-equations closed by two-equation k ¡ " turbulence model together with wall functions. The thermal strati¯cation is modeled using transport equation for the potential temperature. The ¯nite volume method and the explicit Runge{Kutta time integration method are utilized for the numerics.
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Colloquium Fluid Dynamics 2010
Jonáš, Pavel ; Uruba, Václav
The purpose of the Colloquium is to bring together experts on theoretical and experimental fluid mechanics from the academic institutes, universities and other research and development establishments and to offer the opportunity to exchange and update information on the solved problems and to serve as a forum for discussion with leading scientists.
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SPATIO-TEMPORAL ANALYSIS OF SWIRLING JET UNSTEADY BREAKDOWN
Uruba, Václav ; Oberleithner, K. ; Sieber, M. ; Hladík, Ondřej
The swirling jet breakdown unsteady process has been examined experimentally using stereo PIV time resolved method. The experimental setup has been designed, build and prepared in HFI. It generates helical swirling jet and allows implementation of the jet breakdown. The Bi-Orthogonal Decomposition (BOD) method has been chosen for the data analysis the Proper Orthogonal Decomposition applied both in space and time. the BOD method offers decomposition into energetic modes in space (toposes) and in time (chronoses).
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Infrared Thermography as a Visualization Tool of Flow Control by Vortex Generators
Součková, Natálie ; Kuklová, J. ; Popelka, Lukáš ; Matějka, M.
This paper focuses on a suppression of the flow separation, which occurs on a deflected flap, by means of vortex generators (VG's). An airfoil NACA 63A421 with a simple flap and vane-type vortex generators were used. The investigation was carried out by using experimental and numerical methods. The data from the numerical simulation of the flapped airfoil without VG's control were used for the vortex generator design. Two sizes, two different shapes and various spacing of the vortex generators were tested. The flow past the airfoil was visualized through two methods, namely oil and infrared thermography visualization. The lift curves for both cases without and with vortex generators were acquired for a lift coefficient improvement determination. . The experiments were performed in closed circuit wind tunnels with open and close test sections. The improvement was achieved for several cases by means all of the applied methods.
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Experimental study concerning stimulated outflow from porous structures
Pražák, Josef ; Biskup, B. ; Šír, Miloslav
It is generally supposed that the water flow in massive spates occurring in small catchments areas have two components. The first one is the direct surface flow of the water from a preceding rain (new water) the second one is caused by the water “pending” in the soil already before the rain (old water) stimulated by the rain to flow out. The stimulated outflow has been studied in a series of experiments. It was found that in laboratory test, a situation where the stimulated outflow exceeds the stimulating inflow can be simulated in an easy way.
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PIV investigations of an excited air jet
Tesař, Václav ; Uruba, Václav ; Něnička, Václav
Authors investigated an axisymmetric jet of air issuing from a 40 mm dia. nozzle using 3D particle image velocimetry system. The jet was excited by a rotating acousticpressure field in the nozzle exit plane to ensure generation of two helical instability modes chasing one another and mutually interacting. The excitation signal was also used for ensuring PIV data acquisition at a precise phase position
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Turbulence spectra evaluation using a similarity model
Tesař, Václav ; Kordík, Jozef
Authors measured instantaneous velocities in points along the axis of a synthetic jet and evaluated there the spectral density of the measured values. Analysis of these spectra necessitates knowledge of quantities - such as the dissipation rated of eddies – difficult to evaluate and usually not know. In the present case they were found from to the earlier performed fit to quasi-similarity solution of the flowfield, based upon the one-equation model of turbulence.
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