Preliminary propeller erosion tests have been conducted at the Naval Surface Warfare Center Carderock Division 24 inch variable pressure water tunnel (VPWT), shown in Figure 1, to establish testing procedures for evaluating various coatings to minimize cavitation erosion damage to marine propellers. A severe wake field was produced using a two dimensional, thick foil ahead of a downstream driven propeller model. This approach was derived from similar tests conducted by Miller [11]. Conventional cavitation viewing was performed with cameras viewing through the tunnel side window. Images were acquired using high speed (up to 6000 fps) and high resolution (2K x 2K) cameras. In addition, a waterproof camera was mounted inside the foil looking directly downstream at the suction face of the blade. Two propellers were tested, a 16 inch (0.406 m) diameter propeller 5388 and a 12 inch (0.305 m) diameter propeller 4119 [8]. The foil wake field was measured with LDV surveys. Accelerometers were mounted in the water tunnel test section to measure acoustic emissions of cavitation activity. Cavitation erosion was observed at the tip of the 16 inch diameter propeller due to excessive tip vortex, and complicated vortex collapse. Moderate erosion was also observed at the inner radii, where leading edge sheet cavitation collapsed. Scanning techniques for quantifying propeller erosion damage were evaluated. These studies will transition to the 36-inch VPWT where a number of geosym propellers of different materials and coating will be assessed in a similar wake field.http://deepblue.lib.umich.edu/bitstream/2027.42/84210/1/CAV2009-final156.pd
