Annular synthetic jet used for impinging flow mass-transfer

An annular synthetic jet was investigated experimentally, both with and without an opposing impingement wall. The experiments involved smoke visualization and mass transfer measurement on the wall by means of naphthalene sublimation technique. Two qualitatively different flow field patterns were identified, depending upon the driving amplitude level. With small amplitudes, vortical puffs maintain their identity for a relatively long time. If the amplitudes are large, breakdown and coalescence of the vortical train is much faster. Also the resultant mass transfer to the impingement wall is then much higher. Furthermore, a fundamental change of the whole flow field was observed at the high end of the investigated frequency range, associated with radical reduction of the size of the recirculation bubble

Investigation of Vstol Aircraft Engine Surge Due to Ground Vortex Ingestion

An investigation of flow instabilities in the inlet ducts of a two-engine vertical takeoff and landing aircraft DP-1C is described in this paper. The engines stalled during run ups while the aircraft was perated on the ground. These pop stalls occurred at relatively low power levels, sometimes as low as 60% of the engine full speed. The main focus of the paper is on instrumentation of the aircraft intake ducts and on high speed recording the flow instabilities during the engine rotating stall and surge events. The recorded data sets show the history of speeds of both engines and the associated history of pressure changes recorded by six pressure transducers installed in both inlet ducts. Analysis of recorded unsteady pressure data indicated that engine stalls were evoked by a sudden ingestion of a vortex generated between the two streams moving in the opposite directions: hot gas flow close to the ground streaming outbound from the main nozzle and inbound flow above in the engine inlets. The engine stall problem was eventually resolved by modifying the overall flow pattern at the engine intake lips by deploying a suitably shaped double scoop flow deflector

Intelektová deteriorace a vizuomotorická koordinace u žen závislých na alkoholu a jiných návykových látkách

Katedra psychologieFilozofická fakult

CFD Investigation of the test facility for forced blade flutter research

With the increasing share of renewable power resources turbomachines need to be operated under a wider range of operating conditions including highly off-design regimes. Under such regimes an undesirable phenomenon of blade flutter might occur and possibly destroy the machine. To prevent this, intensive research is conducted by research teams worldwide. Blade flutter research program at the Institute of Thermomechanics of the Czech academy of sciences (IT CAS) mainly aims to advance experimental techniques for investigation of sonic and transonic blade flutter. For this purpose, the new sophisticated test facility was designed and manufactured. As part of the design process, the CFD computations were conducted in order to investigate the flow field in the test facility. This paper presents results of these computations with detailed analysis of flow structures occurring during the air flow through the stationary blade cascade