Experimental study on high frame rate characteristics of dynamic flow field of jet in crossflow

Despite the decisive influence of various vortex structures of a jet in crossflow on the jet trajectory and scalar mixing, there are few studies related to the high-frequency dynamic characteristics of shear-layer vortexes during transportation. This paper focuses on the high-frequency flow field characteristic, the scalar concentration distribution and the formation and collapse process of the turbulent microstructure of the jet in crossflow with different nozzle diameters and velocity ratios using 40 kHz Particle Image Velocimetry (PIV) and 20 kHz Acetone Planar Laser Induced Fluorescence (Acetone PLIF). The experimental measurements of the velocity and scalar field show that: increasing the velocity ratio promotes the expansion of the circulation zone behind the jet; in the near field of the jet trajectory, power law fitted velocity distribution and shear-layer vortex trajectory shows an exponentially decrease of the jet velocity, the shear-layer vortex strength and vortex motion frequency also show a downward trend, with the frequency of the shear-layer vortex on the windward side slightly lower than that on the leeward side; as the jet velocity increases, the frequency of the shear-layer vortex increases gradually, but the Strouhal number decreases.