The Research Of Dynamic Characteristics In The Process Of Inclined Water Exit Of Supercavitating Vehicle

When the velocity of the object reaches a certain level, it will cause the phenomenon ofcavitation, cavitation will cause mechanical damage in early time. People are keen to avoid theoccurrence of cavitation. However, when the researchers find that supercavity can decrease thedrag of vehicle, they began a large number of researches on supercavity, especially in themilitary torpedoes and other military applications. But the most studies on underwater vehiclemovement are concentrated in the vertical out of the water or into the water, and there is lessresearch on inclined water exit of a supercavity. In the process of inclined water exit, thedirection between inertial force and the gravity is not in one straight line. The force of inclinedwater exit is more complicated than that of vertical water exit, which causes the supercavitycontour is affected to some degree. Based on the above background, this paper presents someresearch about inclined water exit of a supercavity.By varying aspect ratios, head type of bodies, launched velocity, launched angle, theinclined water exit process of vehicle is recorded by high-speed photography with the visualizingexperimental device. Research about the influence of these factors on the supercavity’s formationand collapse, calculate and analyze the pattern of their hydrodynamic parameters, and verifiedsome conditions through numerical simulation. It is found that the inclined water exit of avehicle will produce a very long cavitation track tail, and will produce asymmetric splash whenpassing through the surface. It is found that the contour of the supercacitation with water-exitangle is not symmetrical, but thick above the vehicle, thin below the vehicle. The closer thevehicle moves to the surface, the more asymmetry of the supercavity. It is found that for sameliquid height, the different head shape of the vehicle will cause different pressure in whichsupercavity can closed completely. When the supercavity does not close in the water, thesupercavity track tail will go on moving and produce the phenomenon of close by breaking withrear supercavitation. Compared the measured contour of supercavity in experiment withLogvinovich empirical formula, we find that the shape in the whole is similar, but in detail thevalue in the lower half of the experiment is a little smaller than that in the theoretical study.Using numerical simulation method to simulate the process of inclined water exit about different head shape of projectile, different launched angles, and having a intuitive understanding aboutthe produce, grow and collapse about a supercavity. The cavity begins to produce in the tail ofthe projectile, then at the shoulder of the projectile, and the cavity keeps on moving and growinguntil it develops into supercavity, we compared the phenomenon in the numerical simulationwith that in the experiment, find the asymmetry of the supercavity, validate parameter setting inthe numerical simulation is correct. In addition, we also analyze the pressure distributionsurrounding the vehicle, explain the reason of asymmetry.