Observations of the Various Types of Limited Cavitation on Axisymmetric Bodies

Abstract

Observations are presented of various types of limited cavitation on 5.1 cm diameter Schiebe, hemispherical, and DTNSRDC noses. These three noses were selected to give various flow states over the range of test speeds 6.1–21.3 m/s ranging from laminar separation for all speeds (hemispherical nose) to nonseparated flow for all speeds (Schiebe nose) with the DTNSRDC nose experiencing both separated and nonseparated flow over the speed range. The types of cavitation observed fall into two broad classes, namely transient and attached. Transient cavitation was observed in three forms, namely travelling-bubble, travelling-patch and bubble-ring. Three types of attached cavitation were observed, namely band, fixed-patch and developed. Bubble-ring and band cavitation are observed only on a body with laminar separation as noted previously by Arakeri and Acosta. Bubble-ring cavitation has been observed only on hemispherical and eighth caliber ogive noses. The desinent cavitation numbers for band and bubble-ring cavitation on the hemispherical nose are related to measured mean and fluctuating pressure data. Travelling cavitation was the most prevalent type of cavitation and the cavitation number decreased with speed and increased with air content. An analysis of travelling cavitation data from several investigations is presented. The cavitation number for fixed-patch cavitation increases with speed which suggests that surface roughness effects are involved.