Experimental study of unsteady evolution characteristics of ventilated air mass on the cylinder surface

The ventilated air film covered by the surface of the underwater vehicle has an important influence on its hydrodynamic characteristics. In this paper, the development characteristics of the vehicle shoulder ventilated air mass under different environmental pressures and ventilation pressures are studied through experiments. The results show that in the ventilation process, the ventilated air mass reduces the scouring effect of the incoming flow on the exhaust holes and ensures the continuous discharge of the air flow. With increasing ventilation pressure, more gas in the ventilated air mass is entrainment into the ventilated cavity, which can improve the circumferential coverage of the ventilation cavity to the vehicle and increasing the size of the ventilation cavity by about 26.4%. When the ratio of ventilation pressure to environmental pressure is reduced, the occurrence of a re-entrained jet can be restrained, and the entrainment at the end of the ventilated cavity is weakened, which reduces the maximum size of ventilation cavity by about 61.5%. •The maximum reduction of the pressure ratio can reduce the size of the ventilation cavity by about 61.5%. .•When the ventilation pressure is doubled, the length of the ventilated cavity increases by about 26.4%. .•The increase of cavitation number can restrain the occurrence of re-entrained jet. .