Experimental Study on Cavity Characteristics of Low Speed Water Entry of Cylinder Based on High-Speed Imaging Technology

During the launching of the underwater vehicle especially in air-launching, the water entry problem is complicated. Factors such as nose shape, water entry velocity, water entry angle, surface property and specific gravity will have a profound effect on the cavity shape, which will affect the initial trajectory and attitude of underwater vehicle. A launch platform with variable launch velocity and multiple launch angle is designed and constructed independently. Launch platform, water tank, high-speed camera, floodlights and synchronizing device together constitute the experiment platform. Five kinds of nose shapes with different hemispherical angles are used. A series of experiments are carried out to investigate how nose shape, water entry velocity and water entry angle will affect the cavity characteristics. The conclusions are performed and the three different cavities (flow separation cavity, weak flow separation cavity, cavity behind the moving cylinder) formed during water entry process are observed and analyzed originally.