Supercavitation phenomenon research of projectiles passing through density change area

The past research on the supercavity flow mostly focused on the homogeneous fluid medium, ignoring the influence of the sudden change of the medium density. We present results from numerical study of moving projectile passing density change zone, both from low-density zone to high-density zone and from high-density to low-density. Particular attention is given to the cavity variation when projectile voyaging through different liquid density areas. And the influence of the cavitation number on the cavity variation is also studied. Research results show that there is a ‘diameter shrinkage’ phenomenon when the projectile moving pass the density jump area. The location of ‘diameter shrinkage’ is relative to the density change model: moving from high density side to low, it appears at the interface of liquids; while moving from low density side to high side, it occurs at low density side not the interface. And the degree of ‘necking’ have something to do with the density difference of two sides. However the effect of cavitation number is much complex, the ‘necking’ phenomenon at the interface showed disorder maybe due to the sample limit, but the re-development of the cavity after passing through the interface showing obvious regularity with the cavitation number.