The rotational effects on the cavitation process for a cylinder vehicle

The effects of rotational motion around the central axis of a supercavitating underwater cylindrical vehicle are numerically investigated with the cavitation process at a cavitation number of 0.0198. The relationships among tangential velocity, streamwise vorticity, flow field pressure distribution of the flow field, mass transfer rates of water and water vapor, and cavity shapes are analyzed under varying rotational speeds. Compared to non-rotational motion, the distinct cavitation mechanisms in rotational motion are identified. The results indicated that during the initial cavitation stage, the tangential velocity near the vehicle's surface rises as the rotational speed increases, gradually decreasing the pressure and transforming water into water vapor. Simultaneously, the concave structure at the end of the front cavity near the vehicle's surface progressively disappears. This accelerates the cavitation process, causing the earlier merger of the front and rear cavities. Following this process, a concave structure appears at the center of the cavity tail for the non-rotating vehicle due to the pressure increase. However, this concave structure gradually transforms to a convex structure with increasing rotational speed. This phenomenon is attributed to the tangential velocity generated by the vehicle's rotation, which causes the pressure in the rear cavity to rise very slowly, and the low-pressure region contracts toward the axis line. The mass transfer in the rear cavity of the rotating vehicle is significantly improved with pressure changes, transforming from vapor into water. Therefore, the pressure changes and mass transfer rate induced by rotation lead to converting the rear cavity end from a concave to a convex structure.