Effects of Leading-Edge Vortex Flow on the Roll Damping of Slender Wings

The leading-edge suction analogy of Polhamus, which has proven useful for lift and drag predictions, has been extended in an effort to understand the vortex-flow effects on the roll damping of slender wings at subsonic speeds. Comparisons with experiment indicate that the method can be useful in the prediction of the large increase in roll damping with angle of attack associated with leading-edge vortex flow of highly swept, low-aspect-ratio wings. In addition, the newly developed forced-oscillation roll mechanism, suitable for testing at subsonic and transonic Mach numbers, has been used to obtain subsonic roll damping data on a series of 74° leading-edge sweep wing planforms. These data illustrate the effects of vortex flow on the damping-in-roll parameter of delta, arrow, and diamond planforms.