Further analysis of self-induced roll oscillations of a non-slender delta wing

In low-speed wind turmel tests at alpha = 25 and 30 degrees of a 45 degrees delta wing with semicircular leading edges limit cycle oscillations occurred around the 50 degrees roll trim angle. In some cases the oscillations were highly regular. in other cases, highly irregular. Air analysis of the observed roll-oscillation dynamics has shown that several viscous flow phenomena are involved, which depend strongly on the leading-edge geometry, and whose relative importance can vary dramatically, with the existing Reynolds number in critical flow regions. The possible role of surface roughness in modifying the viscous flow-motion coupling to cause these dramatically different test results is examined.