Abstract
A slender cylinder in free fall exhibits an autorotation, with is known as flat spin. In order to investigate the flat spin motion, a short cylinder with its length to diameter ratio of 2 is selected and tested in a low-speed wind tunnel. Three different models are prepared, which differ in the positions of the center of gravity. These models are attached to the test device which allows the model to rotate in three axes. The Reynolds numbers of the tests are in a range of 6.7×10^4〜1.3×10^5, which are lower than the critical ones for a 2 dimensional cylinder. All the models exhibit flat spin motions, and the rotational numbers of them match to the frequencies of the pitch and yaw oscillations.
