Numerical investigation on drag characteristics of the truncated hemispherical-nose projectile in vertical water entry

Abstract

ABSTRACT In this study, the feasibility of the ALE algorithm in analyzing the drag of a rigid truncated hemispherical-nose projectile at the initial stage of vertical water entry is examined. The water entry process is simulated under the conditions of different dilated half-angles of the head plane (DHAHPs) and muzzle velocities (u 0). The drag coefficient is obtained by dimensionless processing of the drag. The maximum (Cd max) drag coefficients of the initial stage are fitted to obtain the generalised impact laws of water entry. The results show that the larger the DHAHP, the smaller is u 0 and the higher is Cd max. The bivariate fitting formula for Cd max of the truncated hemispherical-nose projectile has high prediction accuracy and wide applicability. The average (Cd ave) drag coefficients of the projectile changes significantly after DHAHP of approximately 40°. This change is related to the wet state of the head.