Wind tunnel investigation of autorotation of plate: The effects of geometry, Reynolds number and rotation direction

This paper presents a wind tunnel investigation of the autorotation of plates. The effects of geometry, the Reynolds number, and rotation direction on the aerodynamics of the plate, including the rotation rate, lift and drag coefficient, are analyzed. The autorotation rate of plate with smaller aspect ratio is more sensitive to the thickness ratio, whereas when the aspect ratio is larger than 1.5, its effect on the sensitivity of the autorotation rate to the thickness ratio can be ignored. The lift coefficient of plate with larger aspect ratio and smaller thickness ratio is larger when aspect ratio is smaller than 2. Otherwise, the lift coefficient increases first and then decreases with an increase in the thickness ratio. Meanwhile, the lift coefficient of plate decreases as Reynolds number increases, and the relationship between the lift coefficient and the Reynolds number is close to a straight line in logarithmic coordinate. Moreover, the clockwise rotation direction leading to upward lift was found to have a higher absolute value of the lift coefficient than the counterclockwise direction leading to downward lift, especially at low rotation rates. However, the drag coefficient, which fluctuates around a constant of 1.3, is independent of such factors.