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Influence of Carrying Frequency Phase Shift of Synthetic Jet Generator on The Noise
Pick, P. ; Matějka, Milan ; Skála, V.
The main topic of this article is the influence of phase shift of neighbouring synthetic jet generators to the flow field past a hump and noise reduction. Syntheetic jet generators are placed in the hump in front of point of boundary layer separation. The carrying frequency of actuating signal, wich is driving the synthetic jet generator, is shifted for about 180°. The modulated frequency, which corresponds to the shading frequency of the flow, is superposed on the carrying signal. Finally, the benefits of phase shift signal of neighbouring synthetic jet generators are described, as far as the produced noise and the total loss coefficient decrease are concerned.
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Colloquium Fluid Dynamics 2012 : Proceedings
Uruba, Václav ; Jonáš, Pavel
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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Rotary slanted single wire CTA - a useful tool for 3D flows investigations
Jonáš, Pavel
The procedure is described of experimental investigation of a statistically stationary generally nonisothermal 3D flow by means of a constant temperature anemometer (CTA) using single slanted heated wire, rotary round the fixed axis. The principle of this procedure is quite clear. The change of the heated wire temperature modifies ratio of CTA sensitivities to temperature and velocity fluctuations. Turning the heated wire through a proper angle changes the sensitivity to components of the instantaneous velocity vector. Some recommendations are presented based on long time experiences, e.g. on the choice of probe, on the probe calibration, to the measurement organization and to the evaluation of results.
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Parametric study of vortex train generated by plasma actuator in dependency on input voltage waveform
Procházka, Pavel P. ; Uruba, Václav
This article is based on previous work of authors. The vortex train is created by a plasma DBD actuator after application of low-frequency amplitude modulation on high-frequency high-voltage carrier waveform. Data acquisition of flow field around actuators will be performed using time-resolved PIV measurement technique in plane parallel to flow and in cross-section. Phase-averaging will be used due to pseudo-periodical character of this process. The vortex behaviour dependency on modulation frequency, duty cycle, voltage value, electrode gap and other parameters will be shown. The generated flow patterns are to be applied for control of a boundary layer.
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Dynamics of flow behind backward-facing step in a narrow channel
Uruba, Václav
The results and their analysis from experiments obtained by TR-PIV are presented on the model of backward-facing step in a narrow channel. The recirculation zone is studied in details. Mean structures are evaluated from fluctuating velocity fields. Then dynamics of the flow is characterized with help of POD (BOD) technique. Substantial differences in high energy dynamical structures behaviour within the back-flow region and further downstream behind the flow reattachment have been found.
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