The principal objective of the work has been to examine the reasons for the variation of vortex breakdown position in results from various investigators on delta wings of equivalent sweep. Flow visualization has been used to determine the position of the vortex breakdown over a series of delta wings, carefully; constructed to be geometrically identical to those of previous investigators. The results obtained were virtually identical to those found in the original investigations, Support interference, tunnel effects, and Reynolds number were found to have little effect. The detail geometry of the wings, particularly the apex, is found to be the most important factor in determining the position of vortex breakdown, This conclusion has implications for tile design of future experiments on vortex breakdown, and also on theoretical or computational models of the problem, A systematic series of tests a ere conducted to examine this effect on vortex breakdown position in order to control the aerodynamic forces, A small apex flap was found to provide about 1 chord movement in vortex breakdown position for a 1-deg change in flap angle.
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