Abstract
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.
Highlights
When the projectile passing through density jump surface, from high density to low density, the cavitation number increase induce the decrease of the cavity size, so the profile of the cavity suite inside the contour of the constant density (k=1)
We mainly focus attention to study from low density to high density phenomenon in the paper
This paper proposed a numerical strategy to investigate the effect of density jump during the evolution process of natural supercavitation
Summary
Experimental and numerical methods are wildly used research ways to study supercavitation phenomenon. Most of these studies focused on the shape of cavitation, conditions of generating supercavitation, the velocity and pressure distributions of flow field, control and stability of the supercavitating vehicles. Various types of available facilities have been discussed by Fedorenko et al. to investigate inertial motion of high-speed supercavitating bodies Despite these experimental studies there remains much to be understood and cavitation is still an area of ongoing research. We performed a numerical investigation on supercavities under the cavitation number of 0.02 in a constant density media and compared the numerical results with the theoretical calculations and experimental results to confirm the accuracy of the numerical method. The supercavitation mechanism and the change of cavitation shape in different density ratio regions under different cavitation numbers for supercavitation projectiles are discussed respectively
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