Experiment of cavitation and ballistic characteristics of slender body underwater movement

Experimental studies of the slender body's underwater movement were conducted using high-speed camera. Based on the results from the experiment, we examined the characteristics of the cavitation and ballistic of the slender body moving underwater. The experimental results show that the slender body's underwater movement is accompanied with a supercavity, and the slender body's movement and rotation occur in the supercavity except for the contact between the slender body's head and the supercavity wall and the supercavity wall is transparent and smooth except for its tail. The impact between the tail of the slender body and the supercavity wall results from the slender body's rotation in the supercavity, called the tail slap, which serves to stabilize the slender body's movement in the supercavity as a result form the initial perturbation of the flow field. The cavity evolution, closure and shedding were discussed in detail. Series of different flow mechanisms and the relationship between ballistic characteristics and cavity morphology were also analyzed with different initial velocities. The slender body has different accelerations with different initial velocities and the effect of the drag reduction using super cavitation is influenced by factors such as cavity length, diameter and aspect ratio, etc. The initial perturbation angle affects the variation of the angle between the slender body and the cavity axis.