  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.
