On the topology and unsteady behavior of ventilated cavitating flow over a bluff body

The cavity topology and unsteady behavior of ventilated cavitating flow over a bluff body are investigated experimentally using high-speed imaging and particle image velocimetry measurements. It is observed that the cavity topology shows a distinct variation at different Reynold numbers (Re) for a given gas flow rate Q. For gas flow rate Q = 4.16 litres per minute (LPM), the cavity topology is substantially the same at different Re, and the separated shear layer forms the basis for the cavity breakup and shedding vortices. However, for Q = 16.67 LPM, the cavity length decreases, and the cavity topology changes from supercavity to large-scale shedding with the increasing of Re. According to the observations, the balance of gas injection and the gas leakage capacity of shedding vortices, which can be estimated by the cavitation vortex size and the vortex shedding frequency, determines the cavity topology. In addition, the proper orthogonal decomposition analysis indicates that the existence of natural cavitation in the ventilated cavitating flow mainly affects the temporal variation of shedding and makes the periodic change of vortex dynamic more complicated.