Cross-Domain Fluid Dynamics of a Propulsion Wing

The air–water interface exerts a profound influence on cross-domain aircraft during water entry and exit. This study investigates the air–water coupling characteristics of propulsion wings during air–water transition using the volume of fluid method with a sliding mesh. The force and torque coefficients were experimentally validated using a six-component force balance. The research reveals that the propulsion wing in ground effect restrains the diffusion of the downward jet flow generated by the crossflow fan, forcing the airflow to deflect laterally and creating a high-pressure region beneath the wing, thereby enhancing lift by 7.32%. Unlike the rigid interface associated with the ground effect, the flexible interface deforms and dissipates kinetic energy during the propulsion wing in the water effect, resulting in lift degradation. In addition, the propulsion wing experiences a 52.4% lift enhancement during the inverted ceiling effect (ICE) when it approaches the water surface ([Formula: see text]). The mechanism of ICE involves inflow restriction, air–water mixing, and the formation of a large pressure difference. Furthermore, a semi-empirical model developed for the transition process predicts the correlations among depth ratio, rotational speed, forces, and power. These findings provide a theoretical foundation for the control of cross-media aircraft.