Viscous effects in tip vortex cavitation and nucleation

Abstract

This paper is concerned with the physics of cavitation in trailing vortices. The research was aimed at investigating the interrelated effects of the vortex structure and bubble dynamics. The experimental phase utilizes a series of hydrofoils and includes lift and drag measurements, oil flow visualization of the boundary layer flow, and observation of both cavitation inception and disinence in strong and weak water. The complex bubble dynamics inherent in the inception process have been studied using an improved photographic technique. The bubble growth process is strongly dependent on the size and number of nuclei in the free stream and on the strength of the vortex. Numerical simulations indicate that the minimum pressure in the vortex is very close to the tip of the lifting surface, in agreement with the observation that the inception process also occurs very close to the tip under most conditions.