RE-ENTRY JET AND SHOCK INDUCED CAVITY SHEDDING IN CLOUD CAVITATING FLOW AROUND AN AXISYMMETRIC PROJECTILE

摘要

Shedding is one of the most important expressions of the instability of cavitatingflow. Most previous research works were focused on the shedding mechanism induced by the re-entry jet. Shock induced shedding on a wedge is identified recently by using time resolved X-ray densitometry which attracted lots of attention. In the present paper, cavitation dynamics around an axisymmetric body are investigated. Both shock propagation and re-entry jet as inducing factors of shedding are observed in different cycles in a single experiment. Relevant numerical simulations are carried out based on a fully compressible approach under the framework of the open-source code OpenFOAM. Numerical and experimental results agree well with each other. Results indicate shedding is induced by the reentry jet in the first cycle. Re-entry jet occurs and cut the cavity off on the should which induces the shedding of cloud cavity in the first cycle. However in the second and subsequent cycles, shocks are generated by the collapse of shedding cavities and propagate to the cavity closure and induces stronger re-entry jet. Its effect on cavity instability is indirect which still needs a strong re-entry jet as the medium media.