Inception of Cavitation on Hydrofoil Systems Bath Iron Works, Aug 1952 (0138)
This report is concerned with the inception of cavitation in flows about bodies pertinent to hydrofoil systems for the purpose of determining the influence of various parameters and to form the background for investigations within the cavitation range. The basic phenomenon of cavitation is first discussed with respect to the influence of air content, time of exposure to low pressures, and separated flows. Minimum pressures on airfoils are related to the thickness and lift coefficient; empirical relations involving these parameters are determined which are applicable to a large class of hydrofoil shapes. The use of critical Mach numbers in determining inception values of the cavitation index, particularly for interference flows, is discussed. Cavitation data for several forms of blunt bodies are given. Considering surface roughness elements as blunt bodies an approximate method of predicting the inception of cavitation on roughness elements in a boundary-Payer flow is presented. An empirical formula is derived for the critical speed of hydrofoils and broad conclusions deduced from this study are stated.