Experimental study on the influence of the angle of attack on cavity evolution and surface load in the water entry of a cylinder

Abstract

The characteristics of cavity evolution and surface load in water entry by a constrained-posture cylinder at different angles of attack are experimentally investigated. High-speed photography is used to capture flow behaviors, and a measurement system is established to measure the pressure on the surface of the cylinder and its acceleration during the process of water entry. The experimental results show that when the cylinder enters the water at a certain angle of attack, the cavity shows an obvious asymmetry. Comparison of angles of attack shows that the cavity evolution and load characteristics during the water entry process are closely related to the angle of attack of the cylinder. Increasing the angle of attack can short the period if cavity pinch-off but prolong the time of surface seal. Meanwhile, the peak value of impact pressure shows a gradual downward trend with the increased angle of attack, and the relationship between the duration of high load and the angle of attack is approximately linear. Moreover, the characteristics of the flow field play an important role in the surface load of the cylinder, an obvious and short-lived negative relative pressure will appear on the surface of the model inside the cavity at the initial stage of water entry, the part of cylinder that is not affected by the cavity and directly interacts with water has a continuous positive pressure trend. In addition, in can be found that there is a significant pressure fluctuation when the cavity separation line passes over the surface.