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Low Speed Operations
Glinz, Jan ; Daněk, Vladimír (referee) ; Šošovička, Róbert (advisor)
This thesis explains the problems of low speed operations. It aims at stall speed, calculating the stall speed and factors affecting the stall speed. One chapter is about stall warning and safety devices. Another chapter deals with influence of the low speed operations at airplane and the way to piloting it.
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Low Speed Operations
Glinz, Jan ; Daněk, Vladimír (referee) ; Šošovička, Róbert (advisor)
This thesis explains the problems of low speed operations. It aims at stall speed, calculating the stall speed and factors affecting the stall speed. One chapter is about stall warning and safety devices. Another chapter deals with influence of the low speed operations at airplane and the way to piloting it.
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Mechanically modulated nozzles
Tesař, Václav
There are applications in which jet-generating nozzles are requested to have variable properties, responding to a mechanical input action. The paper studies nozzles with a needle - a component with tapered end inserted into the nozzle exit channel. Axial movement of the needle varies the cross-section area available for the flow. Author made laboratory and computational investigations of the simplest shape: a sharp-point cone inserted into a sharpedged, constant-diameter exit channel. Presented examples from accumulated data discuss pressure measurements: overall pressure loss, pressure distribution on the cone surface, and on surfaces of the exit channel.
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Modelling of the boundary-layer transition in the low-pressure turbine blade cascade
Straka, P. ; Příhoda, Jaromír
The paper deals with the application of a algebraic model of the bypass transition in attached and separated flow. The model was applied for flow in a low-pressure turbine blade cascade, where the flow field is strongly influenced by the transition in the separated flow. The aim is to points out some shortcomings of the current transition model and its modifications are proposed. Presented results of modelling are compared with the experimental data.
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Experimental investigation of turbulent flow in a channel with the backward-facing inclined step
Příhoda, Jaromír ; Kotek, M. ; Uruba, Václav ; Kopecký, V. ; Hladík, Ondřej
The work deals with the experimental investigation of turbulent flow in a closed channel with the backward-facing inclined step. Experiments were carried by means of the PIV optical measuring method in the channel of the rectangular cross-section in the inlet part and with inclined steps of the constant height and various inclination angles for a wide range of the Reynolds number. The attention was paid especially to the separation region behind the step and to the relaxation of the shear layer after the reattachment in the outlet part of the channel. The dependence of the length of the separation region on the inclination step angle. Optical measurements were completed by the measurement of static pressure distribution in the inlet and outlet part of the channel to estimate energy losses.
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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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Modelling of subcritical free-surface flow over an inclined backward-facing step in a water channel
Příhoda, Jaromír ; Zubík, P. ; Šulc, J. ; Sedlář, M.
The contribution deals with the experimental and numerical modelling of subcritical turbulent flow in an open channel with an inclined backward-facing step. The step with the inclination angle 20 deg was placed in the water channel of the cross-section 200x200 mm. Experiments were carried out by means of the PIV and LDA measuring techniques. Numerical simulations were executed by means of the commercial software ANSYS CFX 12.0. Numerical results obtained for two-equation models and EARSM turbulence model completed by transport equations for turbulent energy and specific dissipation rate were compared with experimental data. The modelling was concentrated particularly on the development of the flow separation and on the corresponding changes of free surface.
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