Numerical investigation on the inhibition of porpoising instability for high-speed amphibious vehicles

Abstract

ABSTRACT Porpoising instability may occur in high-speed amphibious vehicles with certain hull shapes and structural properties, resulting in speed limitations and severe safety risks. This study analysed the causes and inhibition of porpoising instability by theoretical and numerical methods. The pitch-heave-coupled model of amphibious vehicles was established based on the linear hydrodynamics assumption. After obtaining the hydrodynamic coefficients of forced pitching and heave, the Routh–Hurwitz criterion and eigenvalue extraction method were then employed to assess the stability of the vehicle’s longitudinal motion. The result of the linear stability analysis was compared with numerical simulation and experiments, showing good agreement. Research manifested that trim angle is a crucial factor affecting porpoising instability. Once the instability is mitigated, the resistance will also be decreased. This indicated the great significance of restraining porpoising instability for the comprehensive behaviour of high-speed amphibious vehicles.