An experimental study of the water entry trajectories of truncated cone projectiles: The influence of nose parameters

Abstract

We report on an experimental study of the trajectories of truncated cone projectiles on water entry. The water entry trajectory stability is of great significance to the motion control of projectile. In this paper, the truncated cone nose shape can be described by the area of the leading plane and the cone angle α. Two high-speed cameras are used to capture the trajectories of the projectiles and the initial stage of cavity dynamics. We reveal that the trajectory stability of a projectile is highly dependent on the wetted surface of the nose, which is determined by the location of the separation line between the surfaces of the cavity and body. The increase in the leading plane area is beneficial to the formation of a stable trajectory, in which only the leading plane is wetted. In an unstable trajectory case, the large hydrodynamic moment from the wetted surface on the side of the nose causes a significant rotation of the projectile. However, for the projectile with the cone angle [Formula: see text], though the side of the nose is fully wetted, the trajectory of the projectile turns into stable again. Results show that the attitude deflection of the projectile is determined by the cone angle of the nose. It is also found that the attitude deflection results in an irregular cavity, which further aggravates the rotation of the projectile. We quantify the relationship between the trajectory stability and two nose parameters systematically, and a phase diagram is obtained for a large parameter space. The findings in this work can be used as a reference for future designs to ensure stable trajectories on water entry.

Parallel water entry: Experimental investigations of hydrophobic/hydrophilic spheres

“…Nevertheless, several researchers have also focused on investigating water entry phenomena involving objects with non-spherical geometries. Examples of such objects include conical and wedge-shaped projectiles, [37][38][39][40][41][42][43] flat plates, 1,14,[44][45][46][47][48] vertical cylindrical and slender bodies, 8,32,[49][50][51][52] bodies with asymmetric nose shapes, 53 and thick and thin hollow objects. [54][55][56][57][58] Moreover, studies have explored the water entry behavior of objects with more complex geometries, such as 3D-printed birds and teardrop-shaped objects.…”

Experimental Investigation into the Tail-Slapping Motion of a Projectile with an Oblique Water-Entry Speed

“…Gu et al [32] obtained the weight parameters of the supercavitating projectile and summarized the influence of the weight parameters on the motion characteristics of the tail-slapping. Sui et al [33] studied the influence of geometric parameters of truncated-cone projectiles on the stability of the water-entry process and explored the influence of different wetted areas of the head on the tail-slapping motion. Huang et al [34] investigated the structural deformation, structural vibration and motion stability of the hyper-speed projectile during tail-slapping.…”