Yaw-Roll Coupled Oscillations of a Slender Delta Wing

Abstract

Reported are the results of experiments conducted on a slender delta wing designed to undergo ro ll and yaw oscillations simultaneously. Wind tunnel results indicate that the yaw oscillations always preceded roll oscillations. Time histories show coupli ng between roll and yaw motions. A significant drop in lift coefficie nt was observed during these m otions . There exists a bifurcation angle of attack at which coupled yaw and roll oscillations force the moment coefficients to switch sign. Pertinent results of the ongoing research work are presented . 1-3 . Furthermore, the vortex asymmetry also manifests itself in the form of wing rock. Since this phenomenon is due to the imbalance of lift on the wing, roll divergence sets in with subsequent nose slicing and uncontrolled spin. It is evident that in actual free flights there exists a strong coupling between the roll oscillations and yawing motion. A large body of previous work on delta wing s has focused on roll oscillations and control with the wing constrained in yaw 4-5 . Only limited studies have modeled yaw effects , but only as static sideslips 6-7 and the dynamics of yaw -roll coupling is still missing because of the complexity of the wind tunnel model and the measurements involved. Additional problems arise due to model mounting . As the angle of attack of the model changes, the location of the center of pressure relative to the central pivot point change s which in turn significantly alters the response of the model once the motion set s in. The objective of the present work therefore w as to experimentally investigate the effects of yaw and roll coupled motions on the aerodynamics of a delta wing pivoted at its center of gravity.