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Numerical Simulation of Turbulent Flow Affected by Vortex Generators in Straight Channel
Součková, Natálie ; Šimurda, David ; Uruba, Václav
The presented work is the next step after several experimental examinations of the vortex generator (VG) influence on flow separation occurring on a model of the NACA 63A421 airfoil with a deflected simple flap. The other purpose of this simulation is to obtain beneficial information that can be utilized for the preparation of the experimental investigation of the same configuration using Particle Image Velocimetry method (PIV) in the future. The numerical simulation was performed for one single pair and two pairs of low-profile VGs of the same size, whose heights were smaller than the boundary layer thickness. The rectangular vane type VGs in such configuration, which generates counter-rotating vortices, was examined. The behaviour of vortices produced by VG pair or pairs in several positions downstream the VGs is investigated and will be used as a background of the measurement.
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Visualisation of Boundary Layer Separation and Passive Flow Control on Airfoils and Bodies in Wind-Tunnel and In-Flight Experiments
Popelka, Lukáš ; Kuklová, J. ; Šimurda, David ; Součková, Natálie ; Matějka, Milan ; Uruba, Václav
Infrared camera, Particle Image Velocimetry, smoke-wire, tuft filaments and oil-flow visualization techniques were used for wind-tunnel and in-flight investigation of boundary layer separation, both stall and separation bubbles, related to the low-Reynolds numbers transition mechanism. Airfoils of Wortmann FX66 series and FX66 series wing-fuselage interaction, as well as modern airfoils and their wing-fuselage geometry were subject to study. The presence of previously identified structures in the CFD modelling, such as horse-shoe vortices, was confirmed in the flow.
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Numerické modelování přechodu do turbulence v odtržené mezní vrstvě na profilu
Ďuriš, M. ; Příhoda, Jaromír ; Maršík, František
Práce se zabývá numerickým modelováním přechodu do turbulence v odtržené mezní vrstvě při dvourozměrném proudění stlačitelné tekutiny. Výpočet je založen na řešení středovaných Navier-Stokesových rovnic uzavřených k-omega modelem turbulence a algebraickým modelem zkráceného přechodu. Výpočet je proveden komerčním softwarem ANSYS FLUENT 6.3.26 doplněným funkcemi definovanými uživatelem. Navržený model je porovnán s experimentálními výsledky, získanými pro obtékání leteckých profilů NACA 63A421 a XIS40MOD při různých úhlech náběhu
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Numerical and experimental modelling of transition in a separated boundary layer on the NACA63A421 airfoil
Ďuriš, M. ; Popelka, Lukáš ; Příhoda, Jaromír ; Šimurda, David
The paper is concerned with numerical modelling of transition in a separated boundary layer. A transition model is based on the combination of empirical terms determining position of the transition and averaged Navier–Stokes equations closed by SST turbulence model. The model of transition is applied in computation of 2D flow past NACA63A421 airfoil. Computation is performed using commercial code Fluent 6.3.26, in which the transition model is implemented as a User-Defined-Function. Computed distributions of the pressure coefficient along the airfoil are verified by comparison with experimental data, which were obtained by measurements in a closed circuit wind tunnel at the constant Reynolds number and several angles of attack. The comparison proves the applicability of the implemented transition model.
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An influence of amplitude modulation of the synthetic jet to the flow
Matějka, M. ; Popelka, Lukáš
The paper deals with an experimental research of an active boundary layer control achieved by using periodic excitation of a synthetic jet. An influence of amplitude modulation of the synthetic jet flow control to the flow field of the wake was studied. It summarizes the influence of the basic factors that affect the design of the synthetic jet actuator. The principle of a flow control with and without amplitude modulation was used. Flow visualization of the flow field was done.
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PASSIVE CONTROL OF BOUNDARY LAYER TRANSITION AND SEPARATION
Popelka, Lukáš ; Matějka, M. ; Šimurda, David ; Součková, Natálie
Particle Image Velocimetry, smoke-wire, tuft filaments and oil-flow visualization techniques were used for wind-tunnel and in-flight investigation of boundary layer separation, both stall and separation bubbles, related to the low-Reynolds number transition mechanism. Airfoils of three Czech-designed sailplanes and their wing-fuselage interaction were subject to study. Experimental data were coupled with numerical modeling and synthesis gained. Effect of passive flow control devices - vortex generators - was surveyed, counter-rotating vortex generators and Zig-zag type turbulators were applied. Separation suppression was reached and consequent drag coefficient reduction of test aircrafts measured in flight. Investigation was further extended by PIV Time-Resolved technique.
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Visualization of Flow Separation and Control by Vortex Generators on an Single Flap in Landing Configuration
Součková, Natálie ; Kuklová, J. ; Popelka, Lukáš ; Matějka, Milan
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 three methods, namely tuft filaments technique, oil and thermo camera visualization. The experiments were performed in closed circuit wind tunnels with closed and open test sections. The lift curves for both cases without and with vortex generators were acquired for a lift coefficient improvement determination. The improvement was achieved for several cases by means all of the applied methods.
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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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