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Development and testing of an aerodynamic marine propeller test facility : an investigation into making boats fly Davis, Karl Richard

Abstract

Current techniques for performance testing marine propellers involve the use of extremely expensive facilities such as towing tanks or cavitation tunnels. These methods are also limited as to the maximum propeller size they can test. If it were possible to perform such testing in a more commonly available wind tunnel, marine propeller testing and research could be carried out more widely and upon larger propellers. A device for testing marine propeller performance in a wind tunnel has been designed, built and commissioned. The device features a marine propeller that is 24 inches in diameter that can be spun at up to 3000rpm. Instrumentation for measuring the propeller's thrust, torque, rotational speed and the wind tunnel free stream velocity are integral features of the device. Dimensional analysis was applied to ensure the applicability and validity of the results determined in air to the hydrodynamic case. A series of tests were performed with the equipment to investigate the repeatability of the results, the effect of varying Reynolds number, and to evaluate the device as a comparative tool. The repeatability was found to vary with test conditions. For the preferred test speed of 1500rpm, a repeatability of 1.3% was achieved at peak efficiency. The Reynolds number investigation showed that as the Reynolds number increased, the Reynolds number dependence of the results was reduced. The goal, however, of finding a test speed which exhibited Reynolds number independence was not achieved. The comparative performance test involved testing two identically specified propellers. Subtle differences in the performance characteristics of the two propellers were observed.

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