Characteristics of bubbles-collapse pressures on a Karman-vortex cavity.

Abstract

The flow patterns and the bubbles-collapse pressures on the Karman-vortex cavity behind a circular cylinder are investigated for Reynolds numbers ranging from 4.5×105 to 6.0×105 and cavitation numbers, 0.9 to 1.6. The time history and the intensity distribution of the pressures are messured with a pressure transducer and pressure-sensitive films, respectively, fixed on the side walls of a cavitation tunnel test section. The cavitation aspect is observed by high-speed cinematography. The bubble collapses are frequently induced at the instant of the separation of the Karman-vortex cavity from the cylinder or the cavity itself. The high impulsive pressures with spike pulses over 60MPa occur in the separation or first formation region of it, and as the cavitation number decreases, their regions are combined into one. For an increase in Reynolds number, the distributions of the impulsive pressures show qualitatively the same tendency because they have the same Strouhal number, but the pulse frequency and maximum local impulsive pressure quantitatively increase.