Tip Vortex Cavitation Characteristics and Delay of Inception on a Three-Dimensional Hydrofoil

摘要

A research program was conducted to investigate both the fundamental aspects of, and techniques for delaying, tip vortex cavitation on a three-dimensional hydrofoil. The specific concepts considered for delaying tip vortex cavitation included: a bulbous tip, an artificially roughened tip, and a mass injected tip. The experiments were conducted in the David W. Taylor Naval Ship Research and Development Center 24-inch cavitation tunnel, where the effects of the various concepts on both foil tip vortex cavitation inception and performance were established. These measurements were made at a Reynolds number R subscript c, based on root chord length, of approximately 5,000,000. Some of the more fundamental aspects of the tip vortex rollup process have been documented through the use of flow visualization techniques. The results for the tip vortex cavitation delay concepts indicate substantial increases in the tip vortex cavitation inception speed relative to the unaltered tip; i.e., a 94 percent increase for the roughened tip, 38 percent for the bulbous tip, and 54 percent and 33 percent for the active and passive mass injected respectively. These results were obtained over a wide range of foil angle of attack and with little or no measurable loss in foil performance; i.e., no measurable lift decrease or drag increase. (Author)