Structural Design of an Unmanned Aerial Underwater Vehicle with Coaxial Twin Propellers and the Numerical Simulation of the Cross-Domain Characteristics

This paper addresses the structural adaptability and dynamic stability challenges faced by unmanned aerial underwater vehicle (UAUV) during the transition between air and water. To overcome these issues, this paper innovatively proposes a UAUV that uses coaxial twin propellers for propulsion and conducts a detailed overall structural design and subsystem design for it. Accurate prediction of the kinematic characteristics of UAUV during cross-domain motion is of great significance for the design of high-performance UAUVs. Therefore, a numerical simulation method for UAUV cross-domain motion based on the STAR CCM+ (version 202402) software, the volume of fluid (VOF) method, and the dynamic fluid body interaction (DFBI) module was established. The results showed that when the water-entry speed is small, as the water-entry angle increases, the UAUV’s movement trajectory will exhibit continuous undulating motion. Moreover, during the water-exit process, the smaller the water-exit speed and angle, the greater the change in attitude. The analysis of the dynamic characteristics of cavitation during the UAUV’s water-entry process reveals that the premature rupture of the cavities is detrimental to the UAUV’s movement along the initial entry direction. During the process of the UAUV’s exit from the water, the detachment of water adhering to the UAUV surface will cause certain disturbances to its attitude. The findings of this study provide key theoretical insights and technical references for optimizing the structural design of UAUVs.