Numerical investigation of the water-entry impact performance of a bionic unmanned aerial-underwater vehicle

Numerical investigation of the water-entry impact performance of a bionic unmanned aerial–underwater vehicle (UAUV) is performed. According to the modified SST turbulent model method and volume of fluid (VOF) model, a robust solution procedure for a numerical method is described, and a verification study is conducted on water-entry cases of a cone, hemisphere, and gannet. Biological observation of flying fish has led to the proposal of this three-dimensional modelling approach for water entry processes of bionic UAUVs. The influence of the water-entry velocity and angle on the impact characteristics of a bionic UAUV is numerically investigated by this proposed numerical method. The impact pattern for different water-entry states is used to evaluate the correlation between impact acceleration and the water-entry state. The results indicate the feasibility of investigating the water-entry impact performance of bionic UAUVs in detail. The maximum axial impact acceleration is less than 2.58 g when the water-entry angle is θ ≤ 30° and the velocity is V ≤ 10 m/s. A quadratic relationship exists between the maximum impact acceleration and the initial water-entry velocity, and an approximate cubic relationship exists between the maximum impact acceleration and water-entry angle. The UAUV water entry at too large an angle and too high a velocity should be avoided to avoid a significant impact load.The impact rule investigation of numerical simulation can provide a feasible analysis strategy and a bionic efficient design configuration for UAUV.