A Limited Role of Separation Bubble in Desinent Cavitation

Abstract

In order to clarify whether a separation bubble always plays an important role, the desinence of streamer-cavitation, a kind of attached-cavitation, was carefully investigated in typical internal flows through venturies with and without a 40 μm thin backward facing step under a prescribed cavitation nuclei as well as various hydrodynamic conditions. The following facts have been found: (i) the separation bubble can play an important role in the desinence only when the separation bubble thickness H is larger than the diameter of nucleus dnp that may grow up to a critical one [18], (ii) a marked change takes place in the desinent cavitation number σd due to the step, i.e., σd ≅ |Cps | for H > dnp but σd < |Cps | for H ≦ dnp , (iii) for the cavitation there are two geneses, i.e., the nuclei floating within the separation bubble and the bubble-cloud occurring in the reattachment-region.