On the synergistic interrelation between supercavity formation through vaporous and ventilated routes

A supercavity can be attained via two distinct routes: vaporous and ventilated supercavitation. A vaporous supercavity is one that is obtained by the coalescence of individual vapor bubbles formed by cavitation. On the other hand, a ventilated supercavity results from the coalescence of bubbles of non-condensable gas formed through gas injection at the rear part of the cavitator. A typical strategy of operation of a supercavitating underwater vehicle entails an interplay between these two modes viz. accelerating it to a high speed using ventilation, when a natural supercavity can be sustained. This fact necessitates a systematic study of the synergistic relationship between the process of supercavity formation under these two modes. Thus, in the current work, we have systematically carried out water tunnel experiments to study the effect of vaporous and ventilated modes of supercavitation on each other during supercavity formation. The results show a systematic dependence between the relevant parameters which include the formation natural cavitation number and the formation gas entrainment coefficient. Further, the effects of change in Froude number and blockage are also reported and discussed.