Dual particle image velocimetry (dual PIV) measurements have been performed to investigate the spacetime
correlations in two subsonic isothermal round jets at Mach numbers of 0.6 and 0.9. The correlation scales are
analyzed along the centerline and in the shear-layer center over the first 11 jet diameters from the nozzle exit. To
provide robust results over a wide range of flow conditions, these correlation scales are given in terms of their
appropriate quantities, namely, the mean or rms velocity in reference to velocity and the momentum thickness or the
half-velocity diameter in reference to length in the shear layer and on the jet axis, respectively. From these results, a
discussion on the mode领 of turbulence in jets is addressed. The self-similarity of some space correlation functions
in the shear layer and on the jet axis is shown. Furthermore, far enough downstream in the shear layer, some of the
ratios between the space and time scales are relatively close to the values expected in homogeneous and isotropic
turbulence. It is also found that the ratio between the integral length and the time scales in the fixed frame is of the
order of the local mean flow velocity. In the convected frame, the appropriate sca领 factor is the rms velocity. 德国LaVision PIV/PLIF粒子成像测速场仪 Imager SX PIV相机 用于粒子成像测速(PIV)的荧光示踪粒子
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