Experimental Investigation of the Effect of Trailing-Edge Flaps on Delta Wings

A low-speed wind-tunnel investigation is presented, characterizing the effect of plain trailing-edge flaps on 65 and 70 deg sweep delta wings. Four flap angles and three hinge locations were evaluated. The leading-edge suction analogy was extended to allow estimation of the effect of flaps on both the attached flow and vortex lift components. Additionally, expressions to estimate the drag and pitching moment coefficient were also developed. Comparisons of theory and experiment showed close accord. Flap deflection was observed to cause a notable reduction in the drag coefficient for a given lift coefficient. Wing stall, however, was observed at lower angles of attack than without the flap, caused by an earlier onset of vortex breakdown.