Numerical investigation of vehicle water entry with angle of attack

Abstract

This paper investigates the water entry of a vehicle with angle of attack (AOA) through numerical methods, employing the volume-of-fluid multiphase flow model and overset grid technique. The validity of the numerical model is confirmed through experimental verification. Building upon this, the study analyzes the motion characteristics, cavity evolution, and flow field distribution of the vehicle during water entry, considering the influence of AOA and falling velocity. Numerical findings indicate that the collapse of the right side of the cavity induces a transient lateral force on the vehicle, resulting in vehicle tilting. Moreover, an increase in initial velocity delays vehicle tilt, while an increase in AOA reduces vehicle motion stability, leading to earlier tilting. Initially, the vehicle rotates counterclockwise around the Oz axis of the projectile coordinate system. Subsequent to cavity collapse, the vehicle experiences an opposing moment, leading to a reduction in rotation speed and eventual rotation in the opposite direction. Water impact triggers sudden changes in the vehicle's lift and drag coefficients, while cavity sticking induces a minor abrupt change in the lift coefficient. Following cavity collapse, both lift and drag coefficients exhibit significant oscillations. Unlike typical cavity collapse phenomena, the flow field on the right side of the vehicle undergoes alternating high-pressure and low-pressure regions.