PIV, which stands for particle image velocimetry, it is a method of transient, multi-point, non-contact hydrodynamic velocimetry developed in the late 1970s. In recent decades, it has been continuously improved and developed. The characteristics of PIV technology is beyond the limitations of single point velocity measurement technology (such as LDA), which can record a large number of velocity distribution information on the same transient point, and provide a wealth of spatial structure and flow characteristics of the flow field.