COMPARISONS OF EXPERIMENTALLY DETERMINED AND THEORETICALLY PREDICTED PRESSURES IN THE VICINITY OF A MARINE PROPELLER.
Research and development rept.,
NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER WASHINGTON D C HYDROMECHANICS LAB
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Pressures were measured on a flat plate placed near a model marine propeller in a 24-inch water tunnel. The blade-rate portions of the values measured in uniform flow are compared with field-point pressure predictions of theories for two propeller tip clearances and three advance conditions. Also shown are comparisons between theory and experiment of the separate contributions of propeller thickness and loading. Additional experimental results show the effect of blade number, blade area ratio, and blade skew on propeller-induced pressures. Flat-plate pressure measurements were also obtained near a propeller operating in nonuniform flow and at a cavitating condition in uniform flow. The two theories investigated, field-point pressure calculation methods by Kerwin and by Breslin, both gave good predictions of the magnitudes of the induced blade-rate pressures due to blade thickness. From the experiments it was found that a considerable reduction in induced blade-rate pressure results from increased blade area and extreme blade skew. Propeller blade cavitation increased the induced field pressures. Pressures induced by the propeller while it operated in nonuniform flow tended to be considerably larger than those induced during a corresponding advance in uniform flow and particularly so at off-design advance conditions. Author
- Marine Engineering