On the cavity flow of a cylinder exiting water obliquely

The water exit of a high-speed cavitation vehicle is a highly complex problem. Especially when the vehicle exits the water at different angles, the cavity shape and motion stability are affected by the air-water interface, resulting in significant changes in the mechanical environment and dynamics of the vehicle during the water exit. To solve this problem, a CFD method based on VOF multiphase flow interface-capturing technique and overset mesh technique is adopted to numerically calculate the interaction of vapor-liquid-air multiphase flow during the oblique water exit of a high-speed cylinder. Based on the verification of the computational model by mesh convergence and water-entry experiment, the cavitation evolution and flow distribution characteristics of the high-speed cylinder during oblique water exit is analyzed. Moreover, the effects of water-exit angles on the surface pressure distribution and drag characteristics of the cylinder are studied. The results show that the fluid at the end of the cavity impacts the shoulder of the cylinder during oblique water exit, resulting in the pressure difference between the upper and lower surfaces of the cylinder, which may finally leads to motion deviation. With the decreasing water-exit angle, the negative peak drag coefficient decreases while the peak lateral force coefficient increases, and there is a critical range of water-exit angel for lateral force and pitch angle variation.