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Active control of an annular jet by means of the radial synthetic jet
Broučková, Zuzana ; Kordík, Jozef ; Trávníček, Zdeněk
This experimental study deals with an annular jet, which is actively controlled. Firstly, the following partial tasks were measured: axisymmetric continual jet, axisymmetric synthetic jet, radial synthetic jet, and annular jet without control. Measurement was performed in air by means of the Pitot probe and hot-wire anemometer. The results of partial steady tasks confirm knowledge, available from literature. The expected resonant behavior of the synthetic jet actuators was confirmed too. A possibility of flow control of the mean annular jet was proved. A suitable frequency and amplitude of the control synthetic jet was 600Hz and 23m/s, respectively.
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Experimentální aerodynamický výzkum jako podpora při návrhu turbostrojů
Šafařík, Pavel ; Luxa, Martin ; Šimurda, David
The paper describes a role of experimental aerodynamic research oriented to the support of the design and computauion of turbomachines. The research techniques are briefly introduced. They are namely optical measurements of flow fields and pneumatic measurements by means of traversing. Results of the high-speed aerodynamic modelling of the flow past a blade cascade cascade representing a section in the balding of the last stage of a large output steam turbine are presented.
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EXPERIMENTAL AND NUMERICAL STUDY OF A CONTROLLED PULSATING FLOW
Pírková, L. ; Kopecký, V. ; Trávníček, Zdeněk
A turbulent round air jet discharging into quiescent ambience was studied under circumferential excitation. Four synthetic jet actuators were distributed around the main nozzle exit; they were fed by an electronic control system with a chosen polarity and phase shift. This arrangement allowed to excite the main round jet in several modes, namely the (A) axisymmetric, (B) plane symmetric, (C) bifurcated, and (D) helical modes. The measurement of the excited jet flow fields A–D was performed using the PIV technique. Further, preliminary development of a numerical model of controlled pulsating jet flow is described. Relevant parameters in the numerical model and their effect on model accuracy were investigated. Emphasis is on the mesh density and time step size. This parametric study allowed us to clearly identify a regime of optimal mesh densities and time step sizes for the Reynolds number of interest. The simulations were calculated in Fluent.
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Experimentální mechanika tekutin 2008 - sborník konference
Dančová, Petra ; Vít, Tomáš
The conference will focus on obtaining an overview of projects under investigation, and experimental methods used in the field of fluid mechanics and thermodynamics. Its aim is to organize a network of young research workers who are interested in experimental, and also theoretical, work in the field of fluid mechanics and thermodynamics. The conference should contribute to creating the closer contacts and sharing experience in application of various experimental methods, preparation and implementation of experiments, processing of results and numerical simulations of experiments. Conference proceedings are listed in ISI-Web of Knowledge
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Termoakustický prime mover – demonstrace a prvotní experimenty
Chen, Y.-Ch. ; Vít, Tomáš ; Lédl, V. ; Kordík, Jozef ; Maršík, František ; Wang, A. B. ; Doleček, R. ; Trávníček, Zdeněk
The present paper focuses on an experimental investigation of the thermoacoustic prime mover (sound generator), which was designed with the quarter-wave resonant tube. The working fluid was air under the barometric pressure. This study proves function of the prime mover, and demonstrates variety of experimental methods for experimental investigation of the thermoacoustics: acoustic measurements (the resonant frequency, power spectrum, and sound pressure level), temperature measurement (temperatures along the resonant tube, namely near the thermoacoustic stack), hot-wire measurement (oscillation velocities and displacements), and optical experiments by the holographic interferometry.
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Rezonanční frekvence generátorů syntetizovaných proudů
Kordík, Jozef ; Trávníček, Zdeněk ; Šafařík, P.
This contribution focuses on axisymmetric synthetic jet actuators from the theoretical point of view. In order to evaluate their resonance frequencies, four mathematical models were derived. The results were compared with experimental data, and analyzed. With respect to the theoretical and experimental results, the applicability and limits of the models were discussed. The results illustratively prove correctness of the previous derivation based on transformation of mechanical energy.
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