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An experimental investigation of the autorotation of a flat plate Cheng, Shi

Abstract

Autorotation measurements were made for a 4 inch chord thin plate under approximately two-dimensional flow conditions in a low speed wind tunnel. To determine the instantaneous angular velocity and angular acceleration of the plate, a new technique based on the principle of an angular displacement transducer was developed. The closely linear variation of tip speeds with wind speed and the non-linear characteristics of the build-up time and angular acceleration were investigated in the wind speed range from 10.9 fps to 37. 3 fps. To examine the instantaneous aerodynamic loading on the autorotating plate as a function of angular position of the plate, surface fluctuating pressure measurements were made, with the aid of a pressure transducer and a dynamic pressure seal, and correlated with displacement transducer readings at the wind speed of 26. 3 fps. Instantaneous aerodynamic torque during one autorotation cycle was estimated from the integration of the fluid moments resulting from the instantaneous surface pressure fluctuations. Some discussion of the aerodynamic phenomena is given.

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