Time resolved flow-field measurements of a turbulent mixing layer over a rectangular cavity

摘要: High Reynolds number, low Mach turbulent shear flow past a rectangular, shallow cavity has been experimentally investigated with the use of dual-camera cinematographic particle image velocimetry (CPIV). The CPIV had 3 kHz sampling rate, which was sufficient to monitor time evolution large-scale vortices as they formed, evolved downstream and impinged on wall. time-averaged properties (velocity vorticity fields, streamwise velocity profiles momentum thickness) were in agreement previous studies under similar operating conditions. time-resolved results show that separated layer quickly rolled-up formed eddies immediately separation point. convect at approximately half free-stream speed. Vorticity strength intermittency structures approach edge suggests an increase three-dimensionality flow. Time-resolved correlations reveal in-plane coherence decays within 2–3 structure diameters, quasi-periodic features are present vortex passage frequency ~1 kHz. power spectra vertical fluctuations revealed peak non-dimensional corresponding predicted using linear, inviscid instability theory.