Cavity dynamics of water entry for a head-ventilated cylinder

Abstract

This paper describes the flow field and impact load characteristics of a ventilated cylinder upon vertical and angled water entry. A high-speed camera is used to record the evolution of the cavity, and a pressure sensor placed on the head of the cylinder records the impact load. The results show that head ventilation produces an initial cavity before the cylinder enters the water. This changes the evolution of the cavity, reduces the volume of the cavity, and modifies the cavity closure mechanism. As the ventilation rate increases, the impact load decreases rapidly at first and then stabilizes at a certain level. The angle of attack also changes the flow field and impact load characteristics. In the case of angled water entry, an obvious asymmetric cavity is formed, and then cavity separation occurs. An increase in the angle of attack or the ventilation rate strengthens the cavity separation. The impact load decreases with increasing angle of attack at low ventilation rates but is independent of the angle of attack at high ventilation rates.