Abstract: The water exit of a Trans-Medium Vehicle (TMV) with lateral velocity presents problems, including multiphase flow and load nonlinearity, which affect the stability of the TMV water exit. To solve this problem, this paper proposes a TMV with a killer whale inspired head shape. The bio-inspired asymmetric head shape refers to the deflection degree of the TMV head tip towards the lateral velocity direction. The three-dimensional parameterized geometry is constructed via the two-parameter cubic polynomial. The unsteady Reynolds-Averaged Navier–Stokes (RANS) equations and the Renormalization Group (RNG) k - ε turbulence model are adopted for flow field simulation. Then the dynamic solution is achieved through the 6 Degrees of Freedom (DOF) equations. The flow field and hydrodynamic characteristics with different head shapes are investigated to reveal the mechanism of load reduction and stability improvement. The results show that the asymmetric head shape reduces fluid dissipation energy, retaining more energy in the form of longitudinal and lateral kinetic energy, thereby effectively hindering the conversion of energy into rotational kinetic energy. Furthermore, the asymmetric head shape reduces the inflow-surface pressure, shifts the low-pressure zone toward the head, and suppresses the formation of the hairpin vortex head in advance. Compared with the symmetrical head, the asymmetric head shape can achieve a 93.74% suppression of the attitude angle deflection and an 84.01% reduction of angular velocity. The study provides positive implications for load reduction and stability improvement during the TMV water exit.

Key words: Asymmetric head shape')">Asymmetric head shape, Trans-medium vehicle, Water exit, Load reduction and stability improvement, Multiphase flow