Study on Impact Load and Head Cap Load Reduction Performance of Vehicle Entering Water at High Speed

Aiming at the problem of high-speed entry of vehicles with a diameter of 200 mm, a numerical model of high-speed entry of vehicles is established based on the arbitrary Lagrange–Euler (ALE) algorithm, and the numerical simulation of high-speed entry of flat-nosed and round-nosed vehicles is carried out. On this basis, the experimental research on the entry of vehicle with buffer caps is carried out. The following conclusions are obtained through simulation. The peak value of the axial load of the vehicle raises with the increase of the inlet velocity and angle, while the stable value only raises with the increase of the inlet velocity. The impact load on the round-nosed vehicle is obviously smaller than that on the flat-nosed vehicle when the water entry angle is greater than 80°. The peak value of axial load can be reduced by 22% when entering water vertically at 100 m/s. The following conclusions are obtained through experiments. The buffer head cap has a significant load reduction effect. It shows compaction, cracks and breakage under the impact of water. These processes can absorb part of the impact energy, reduce the peak value of axial load and increase the pulse width. The load reduction rate grows from 4.7% to 18.5% when the length of the buffer head cap is increased from 200 mm to 300 mm while the water inlet speed is the same. The damage level of the head cap increases sharply, and the load reduction rate raises when the water entry speed is increased while the length of the buffer head cap is the same.