Autorotation of rectangular plates

A series of tests have been conducted on the autorotation of plates of rectangular section and thickness to chord ratios of from 0.1 to 1.0. The major difference from previous work was that the plates spanned the full width of the wind tunnel, i.e. the flow was essentially two-dimensional. The results show major differences from predictions of infinite aspect ratio plates inferred from finite aspect ratio tests as given by Iversen (1979). Moreover, they give excellent correlation with the two-dimensional numerical solution of Lugt (1980) for a 10% thick plate. In contrast to previous results which indicate no autorotation for square cylinders (t/c = 1.0), it is found that autorotation is easily achieved. A new result is that tipspeed ratios are found to be independent of thickness ratio, at approximately the Lugt value over the full range of thickness ratios. Drag coefficients are found to be independent of thickness ratio. There appears to be a critical thickness ratio above and below which the lift coefficients are constant, but are of different magnitude.