The Development of the Lift of an Impulsively Started Elliptic Cylinder at Incidence

The time-dependent lift of an impulsively started 2:1 elliptic cylinder at angles of attack 20° and 45° was measured by means of strain gauges. At the initial stage after starting a marked peak in lift occurs and then vanishes. After this, the second peak begins to develop. Flow visualization experiments show that the first isolated vortex makes its appearance in the rear of the elliptic cylinder at the instant when the second peak in lift begins to develop, and that the second peak in lift occurs when the second isolated vortex is about to be released from the back of the elliptic cylinder.