Experimental Unsteady and Mean Loads on a CP Propeller Blade on a Model of the FF-1088 for Simulated Modes of Operation.
DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BETHESDA MD
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Experiments are described in which the mean and unsteady loads were measured on a single blade of a model of the controllable-pitch propeller on the FF-1088. The experiments were conducted behind a model of the FF-1088 hull under steady ahead operation, hull pitching motions, simulated crash ahead maneuvers, and simulated crash astern maneuvers. The experimental techniques are outlined and the dynamometer and data analysis system described. The results show that the circumferential variation of all measured components of blade loading is primarily a once-per-revolution variation, with maximum and minimum values occurring near the angular positions in which the spindle axis is horizontal. For sinusoidal pitching of the model hull with amplitude of 2 deg and frequency of 0.8 Hz, the peak-to-peak circumferential variation of measured forces and moments increased by a minimum of 50 percent over the values without hull pitching. For simulated operation during a crash ahead or crash astern maneuver, the circumferential variation of measured forces and moments varied approximately as the product of ship speed and propeller rotational speed, and was a function of propeller pitch. At no time during the simulated crash ahead or crash astern maneuvers were the circumferential variations of loads as large as during steady ahead operation. For steady ahead operation, circumferential variation of loading determined from the model experiments agreed fairly well with full-scale data, but was substantially larger than the theoretically calculated values. Author
- Marine Engineering