AN EXPERIMENTAL INVESTIGATION OF DYNAMIC GROUND EFFECT

A wind-tunnel investigation has been made at low speed to determine the dynamic ground effect for low-aspect-ratio wings with sharp leading edges at constant angles of attack. The three main purposes of this investigation were (1) to develop a wind tunnel simulation method that could provide dynamic ground effect data, (2) to demonstrate that the dynamic ground effect wind-tunnel testing could produce data comparable to flight test data, and (3) to provide information on the physical mechanisms involved in dynamic ground effect for highly swept delta wings.; The dynamic ground effect data obtained from the wind-tunnel simulation provided a closer approximation to the actual flight test data than do static test data. For highly swept (60(DEGREES) to 75(DEGREES)), low-aspect-ratio wings static ground effect data greatly overpredicted the increase in C(,L), C(,D), and C(,M) as height over the span decreased below .4. For low-swept ((LAMDA)(,LE) < 30(DEGREES)), low-aspect-ratio wings the discrepancy was much less. The visual observations of the flow field confirmed that vortex lag existed for highly swept, low-aspect-ratio wings in dynamic ground effect.