DTIC ADA086482: Vibrations of a Marine Propeller pdf

DTIC ADA086482: Vibrations of a Marine Propeller

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The effect of blade vibration on the unsteady forces developed by an elastic marine propeller is investigated for a controlled laboratory situation. The study involves the development of a theory for a flexible propeller operating in a spatially nonuniform inflow velocity field and a series of experimental tests. Measurements of unsteady propeller forces in a 24-inch water tunnel are presented for two model propellers whose fundamental resonance frequencies are excited by a nonuniform inflow field. Measured unsteady thrust and torque, presented as a function of excitation frequency, show distinctly different elastic effects–one propeller demonstrates a large force amplification near its resonance frequency while the other did not. The simple theoretical model explains the difference as being due to the differing amounts of induced hydrodynamic damping; there is a large hydrodynamic damping in one case and a small amount in the other case. Another result of the study is that blade vibration can significantly reduce the unsteady forces transmitted to the propeller shaft over a certain range of excitation frequencies.

Calculated forces are in general agreement with the experimental measurements. (Author

• Creator/s: Defense Technical Information Center
• Date: 4/1/1980
• Year: 1980
• Book Topics/Themes: DTIC Archive, Brooks, James Emmert, DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BETHESDA MD, *VIBRATION, *MARINE PROPELLERS, *NONUNIFORM FLOW, *PROPELLER BLADES, MATHEMATICAL MODELS, DAMPING, HYDRODYNAMICS, WATER TUNNELS, LIFTING SURFACES

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