Study on structural response of a vehicle during high-speed water entry

To investigate the structural response of the vehicle from water entry to tail-slap, a numerical model based on the Structured Arbitrary Lagrange-Euler (S-ALE) algorithm was established, followed by grid-independence and accuracy validation. Using the validated model, cavity evolution during the whole process was first analyzed, then water pressure contours and shell impact force curves were investigated. Subsequently, the influence law of the tail-slap stage on the stress of the stern section was investigated. Finally, structural responses of the vehicle under varying water-entry angles and velocities were analyzed. Results show that the peak impact force at the moment of entry was more than three times that during the tail-slap stage, while the tail-slap effect significantly increased the stress on the rudder plate. For all entry angles, the impact force at the moment of entry was significantly higher than that caused by the tail-slap effect, with the maximum difference reaching 83.1%. However, the tail-slap effect had a significant impact on the stress in the rudder plate, and as the entry angle increased, the peak stress in the rudder plate gradually increased. As the entry velocity increases, the difference between the impact force at the moment of entry and that during the tail-slap stage widens further, reaching a maximum of 87.8%. At the same time, the vehicle's attitude deviates, causing the tail-slap effect on the rudder plate to weaken. The results of this study reveal the mechanical characteristics of the vehicle structure under the influence of the tail-slap effect. They provide important reference value for the impact-resistant design of the vehicle’s rudder plate and offer a basis for reducing the impact of the tail-slap effect by appropriately selecting initial entry conditions.