Abstract: The supercavitating flows caused by projectiles with 3 different length-to-diameter ratios at 6 different depths of water are studied using a high-speed camera and a horizontal supercavity test apparatus. The research results show that, with the increase in water depth, the cavity’s volume or size becomes smaller and its life time becomes shorter, as well as the drag coefficient of projectile increases. When the projectiles are completely covered by supercavity and their velocities are almost same, the cavity’s volume keeps unchanged with the increase in the aspect ratio, but its drag coefficient increases. As the water depth decreases, the supercavity starts to interact with the free surface. This causes the increase in the cavity’s volume (size) and life time, which is believed due to that the air in atmosphere has entered into the supercavity. For the first time, the interaction process between supercavity and free surface is discussed deeply.

Key words: ordnance science and technology, projectile drag coefficient, shape of supercavity, length-to-diameter ratio, water depth, experimental study