采用双粒子成像测速系统测量双亚音速喷射的时空相关性
Dual particle image velocimetry (dual PIV) measurements have been performed to investigate the space–timecorrelations in two subsonic isothermal round jets at Mach numbers of 0.6 and 0.9. The correlation scales areanalyzed along the centerline and in the shear-layer center over the first 11 jet diameters from the nozzle exit. Toprovide robust results over a wide range of flow conditions, these correlation scales are given in terms of theirappropriate quantities, namely, the mean or rms velocity in reference to velocity and the momentum thickness or thehalf-velocity diameter in reference to length in the shear layer and on the jet axis, respectively. From these results, adiscussion on the modeling of turbulence in jets is addressed. The self-similarity of some space correlation functionsin the shear layer and on the jet axis is shown. Furthermore, far enough downstream in the shear layer, some of theratios between the space and time scales are relatively close to the values expected in homogeneous and isotropicturbulence. It is also found that the ratio between the integral length and the time scales in the fixed frame is of theorder of the local mean flow velocity. In the convected frame, the appropriate scaling factor is the rms velocity.