Experimental investigation on the multiphase flow characteristics of oblique water entry of the hollow cylinders

Abstract

The oblique water entry of the hollow cylinders with various inner diameters has been investigated experimentally. The multiphase flow characteristics of the cavity, through-hole jet and multiscale bubbles have been revealed and discussed. In the experimental setup, a high-speed photography technique is used to capture the process of water entry based on digital video images. The results show that the fluid flows to the inside and outside of the hollow cylinder along the flow separation position, the through-hole jet and cavity are formed. The deep closure mode of the cavity pinched off by line contact appears, the upper cavity moves upward and the secondary jet is formed, and the lower cavity presents the evolution process of stable transparent surface, fluctuating rippling surface, blurry broken surface and collapse. Three bubble clusters are formed due to the closure and pinching off of the cavity, the breaking up of the through-hole jet, and the blurry broken evolution of the lower cavity, and are shedding upward along the moving paths of the upper cavity, the tail and the head of the hollow cylinder, respectively. Moreover, a parametric study is conducted on the effects of inner diameters on the multiphase flow structure and dynamic characteristics.