Hydrodynamic Investigations of a Cross-Domain Vehicle with the Capability of High-Speed Cruising on Water Surface

With the growing demands for marine resource exploitation and marine defense security deployment, unmanned surface vehicles (USVs) and autonomous underwater vehicles (AUVs) are of great value in both civil and military fields. However, both USVs and AUVs can only operate in a single scenario, which is difficult for complex cross-domain missions. Here, we propose a cross-domain vehicle (CDV) with both high-speed mode as USV and diving mode as AUV. To obtain the capability of high-speed cruising on the water surface, two sets of well-tailored hydrofoils are employed for drag reduction by adjusting the attitudes of CDV. Numerical investigations are carried out to evaluate the hydrodynamic characteristics of the CDV at different velocities. Moreover, prototype tests are conducted in open water, demonstrating its technical feasibility and validating the numerical methods. The results demonstrate a maximum drag reduction of 43% and a significant improvement in longitudinal stability with elaborate design of the hydrofoils. The mechanism of the drag reduction is revealed by flow field analysis, which is a joint effect resulting from the inhibition of wave-making as well as the reduction of the wetted surface area. The current work has significant value for future improvement of CDVs.