Experimental investigation on the ventilated cavitating flow characteristics around an axisymmetric body with an unsteady ventilation

Experiments and analyses are conducted for the ventilated cavitating flow around an axisymmetric body with unsteady ventilations, and the parameters of unsteady ventilations (i.e., sinusoidal ventilation) are involved to consider the effect on unsteady cavity flow. At the same incoming flow velocity and ventilation rate, the difference on cavity shape caused by the steady ventilation and unsteady ventilation is mentioned firstly, and the cavity with unsteady ventilation is underdeveloped relatively. Furthermore, pressure sensors are designed to obtain the pressure inside and outside cavity. Results show that there are two recognizable stages according to the ventilation state, such as ventilation increasing stage (VIS stage) and decreasing stage (VDS stage), and the sizes of cavity and foamy shedding in VDS stage are greater than that in VIS stage. Besides, the increased amplitude of ventilation makes the greater cavity unsteadiness and pressure development on the solid surface. On the contrary, the increased frequency of ventilation leads to that the mean size of cavity increases and the cavity flow is approaching to the state under steady ventilation, counterintuitively. Finally, a qualitative analysis is introduced to show that the difference caused different ventilation stages is related to the gas entrainment within the internal boundary layer.