Abstract: Aiming at the problem of un-commanded motion at high angles of attack, we study the roll oscillation of wing-body configurations with strake wings through wind tunnel experiments such as free-to-roll tests, force and pressure measurement, and Particle Image Velocimetry (PIV). The pitch angle zones of roll oscillations are obtained, the dominant flow inducing wing rock revealed, and the triggering, deviation and sustaining mechanisms of roll oscillations discussed. The results show that the wing rock is onset over the wing-body configuration with strake wings at high angles of attack. The roll oscillation can be divided into three areas:fixed-point motion zone one (pitch angle 5°-35°), limit-cycle oscillation zone (pitch angle 37.5°-50°) and fixed-point motion zone two (pitch angle 55°-70°). The limit-cycle oscillation zone can be further divided into the fore-body vortex no-dominant zone (pitch angle 37.5°-45°) and partially-dominant zone (pitch angle 47.5°-50°). The analysis of the wing rock at pitch angles 40° and 50° reveals that the evolution of the wake of the strake wing vortex or merged strake wing vortex at zero roll angle and nonzero roll angle forms the triggering and deviation mechanisms, respectively. The hysteresis of the wake undergoing roll oscillations forms the sustaining mechanism.

Key words: wing rock, strake wings, wing-body configurations, wind tunnel tests, flow mechanism