Water entry of a constraint posture body under different entry angles and ventilation rates

Water entry experiments of a constraint posture projectile were performed under different entry angles and ventilation rates. The near water surface cavity flow characteristics, including splash sheet, surface closure, pull away, deep closure and cavity ripples, were investigated under different entry angles and ventilation rates without the posture perturbation influence of the projectile. The experimental results demonstrate that, the dimensionless cavity surface closure and pull away time increase gradually with the increasing of the water entry angle, and the dimensionless cavity deep closure time and the pinch off depth experience a slight increase and decrease, respectively. The deep closure patterns shift from the point closure to the line closure as the water entry angle increases for the oblique water entry cases. And, the cavity ripples were observed before the pinch off and after the pull away for ours experiment, which are more likely acoustic in origin. In addition, the surface closure contributed by the splash sheet is clearly delayed at similar entry conditions except for the ventilation rate. The dimensionless cavity deep closure times of the ventilation cases are significantly higher than the cases without ventilation. However, with further increase the ventilation, the deep closure time changes slightly.