Aerodynamic characteristics around the stalling angle of the discus using a PIV

This paper describes the hysteresis in the aerodynamic properties of a discus near to its stalling angle. Wind tunnel tests were carried out with a full-size woman’s discus. The experimental aerodynamic data D, L and M were obtained from wind tunnel tests as functions of the angle of attack. It was found that the drag, lift and pitching moment coefficients, CD CL and CM, increase with increasing the angle of attack up to a stalling angle of 29-30°. Beyond the stalling angle, CL and CM decrease suddenly and abruptly with increasing angle of attack. On the other hand, recovery from the stall does not occur at the same stalling angle of 29-30° when the angle of attack decreases from the stall state; recovery actually occurs at 25°. The dependence of CL and CM on the angle of attack is almost the same when the angle of attack is less than 24°. Therefore, hysteresis occurs near the stalling angle. A laminar bubble region is observed in the upstream side of the discus at 28° during the process of increasing the angle of attack, and re-attachment occurs around the convex point of the discus. However, re-attachment does not occur at 26° during the process of decreasing the angle of attack.