AN INVESTIGATION OF METHODS TO REDUCE OR ELIMINATE CAVITATION EROSION OF SHIP PROPELLERS

Erosive impact intensity of cavitation generated by a model propeller in water tunnel flows is related to specific off-design conditions that a propeller experiences in a ship's wake. Uniform velocity flows were used so that effects of off-design conditions could be separated from effects of cavitation dynamics introduced by periodic rotation through the wake. Erosive impact intensity was measured by the size and rate of formation of pits formed on the polished blades by impact of loads created by collapse of cavitation bubbles. Information is also presented on the evaluation as erosion resistant coverings for propellers, of five polyurethane formulations developed by Bell Aerospace Textron and thirteen commercial materials applied by seven suppliers. This laboratory evaluation included cavitation erosion resistance of the coverings and lap shear strengths of their bonds to ABS Type 4 bronze before and after 6 months immersion in salt water.