This paper aims to research the effects of the temperature and compressibility of liquid water on the super-cavitation phenomenon of an ultra-high-speed underwater vehicle and its motion characteristics.

First, based on CFD general software Fluent 19.2, the free motion of transonic and supersonic vehicles is computed using a numerical model that considers both the compressibility and temperature of the water. Qualitative and quantitative comparisons with the experimental results of reference [1] are made, and the effectiveness of the numerical method is verified. The motion characteristics at different initial speeds are then analyzed using the range at the sailing time of 0.008 s as the comparison base. Finally, the influence of the launch depth and environment temperature on the motion characteristics is discussed.

It is found that when the speed is greater than 2 000 m/s, increasing the initial speed does not significantly increase the effective range; the critical speed is found between 1 450 m/s and 1 475 m/s, where the range variation is less than 3% with or without the influence of the temperature; as the launch depth increases, the resistance of the vehicle becomes greater and the sailing range gradually decreases; and the higher the environment temperature, the shorter the effective range.

It is shown that the numerical model proposed herein, which considers both the temperature and compressibility of liquid water, can provide valuable references for the motion analysis of ultra high-speed underwater vehicles and corresponding practical applications.