Design and Improvement of Tandem Twin-Rotor Aerial-Aquatic Vehicle Based on Numerical Analysis

To enhance the air–water adaptability of the aerial-aquatic vehicles (AAVs), an improved tandem twin-rotor AAV design is proposed based on the characteristics and application requirements of air–water cross-domain movement. Computational fluid dynamics (CFD) software was used to simulate the underwater cruising state and dynamic water entry process of the tandem twin-rotor AAV. Results indicate that the underwater cruise resistance of the improved tandem twin-rotor AAV is relatively small. Among them, the two sets of tandem air power systems account for a relatively large proportion of the underwater drag, about 29.8%, while the drag reduction achieved by improving the head shape is around 15.4%. The head shape, water entry angle and speed have a great influence on the water entry trajectory and attitude of the tandem twin-rotor AAV. Following improvement, the tandem twin-rotor AAV demonstrates an enhancement in reducing the deviation of the water entry trajectory, mitigating water surface ricochet and enhancement of water entry depth to a certain extent. The inclination angle should be in the range of 20–30° to alleviate unfavorable outcomes, including prolonged water entry time caused by water surface ricochet at lower entry angles, while concurrently mitigating the heightened impact pressure resulting from steeper entry angles. Higher entry velocities lead to greater impact pressures, necessitating careful consideration of water entry depth and impact pressure to prevent adverse effects on structural integrity.