DYNAMIC PITCH-UP OF A DELTA-WING

The transient flowfield over a delta wing during pitch-up motions to very large angles of attack was investigated. Emphasis was directed at the growth and the eventual breakdown of the leading-edge vortices. Delta wing models were tested in a wind tunnel at Reynolds numbers of order 10(5). The flowfield along the trailing edge was mapped out via a seven-hole probe designed, constructed, and calibrated to generate time-resolved information. Instantaneous surface pressure measurements were also obtained. Earlier qualitative evidence of hysteresis in the development of the flow was confirmed. Moreover, the present data indicate significant differences of vorticity content between the steady and the unsteady motions, for reduced frequencies as low as 0.01.