Research on similarity of water entry load for scaled-down underwater vehicle based on different model test environments

The incompatibility of similarity quotients and the lack of test simulation capability can be effectively addressed by overcoming "similarity constraint" using diverse model test environments (varying parameters such as atmospheric pressure and gravitational acceleration). In order to examine the scaling effects in different model test environments, this paper presents a numerical study of the prediction accuracy of a flat-head scaled-down vehicle for full-scale prototype water entry impacts in the normal compression, reduced compression and hypergravity model test environments using the experimentally validated FLUENT overlapping mesh technique. The study compared and analyzed the pressure load and flow field evolution under different initial conditions. The findings revealed that the over-simulation of the entry cushion effect of the scaled-down model and dynamic pressure in the normal compression environment led to inaccurate prediction of the full-scale prototype. The prediction results improved in the reduced compression environment than in the normal compression environment. However, the cavitation effect was over-simulated and the dynamic pressure was weakened. In contrast, the hypergravity environment enables the simulation of solid and fluid inertia to the same extent, satisfying the scaled-down model for full prediction of the prototype water entry cavity evolution and impact loads.