Effect of mounting strut and cavitator shape on the ventilation demand for ventilated supercavitation

Abstract

The present work reports behaviors regarding the formation and collapse of a ventilated supercavity while varying the cavitator shapes, including triangle, disk, and cone and varying mounting struts. Three cavitators with the same frontal area are fabricated with 3D printing and mounted on a forward facing model (FFM). The ventilation requirements to generate (C_Qf) and sustain (C_Qc) a supercavity are tested over a wide range of Froude number (Fr) for each cavitator and compared with backward facing model(BFM). Compared to the triangle and disk cavitators, the cone-shaped cavitator requires the least amount of air to generate a supercavity in nearly all of the tested flow regime except very high Fr. The C_Qc of disk FFM is lower than that of its BFM counterpart at small Fr and exceeds the BFM C_Qc with further increase of Fr. The cone cavitator has the smallest C_Qc among all the cavitators across the range of Fr in our experiments. Simultaneous internal pressure and cavity dimension measurements are conducted to elucidate the cavity sustenance behaviors. The cone-generated cavity yields a significantly smaller maximum diameter and a shorter half-length. Cavity geometric information and cavity pressure measurements with high-speed imaging of re-entrant jet are employed to estimate the re-entrant jet momentum under different Fr for disk and cone cavitators. The estimated re-entrant jet momentum shows reasonable match with the ventilation air momentum under C_Qc in lower Fr for both cavitator cases, with the disk cavitator case yielding significantly stronger re-entrant jet, providing support to the re-entrant jet mechanism governing on the cavity collapse. Our study sheds some light on the cavitator design and ventilation strategy for a supercavitating vehicle in practice.