Effect of yaw angle on vortex formation over a slender delta wing

In this study, effects of yaw angle, β on the vortical flow over a delta wing which has a 70° sweep angle, Λ were investigated qualitatively and quantitatively by means of different experimental techniques. Experiments were performed as a function of angles of attack, in the range of 25°≤α≤35° and yaw angles in the range of 0°≤β≤20°. Leading edge vortex breakdown locations, trajectories of these vortices and their interactions were observed using dye visualizations. Time-averaged velocity vectors, pattern of streamlines, velocity components, contour of vorticity distributions, turbulence statistics such as Reynolds stress correlations, distribution of fluctuating velocities and turbulent kinetic energy were determined using instantaneous velocities measured by Stereo Particle Image Velocimetry (Stereo PIV). Separation and reattachment lines on the surface of the delta wing were also observed using surface oil visualization. Distribution of pressure coefficients Cp over the surface of the delta wing were calculated using pressure measurements. Results revealed that in the absence of the yaw angle, β symmetrical flow structure forms over the delta wing but when delta wing is yawed symmetrical flow structure is altered considerably. Windward side vortex breakdown location moves upstream, close to the apex of delta wing. Trajectories of the vortices moved towards the central axis of the delta wing. Disordered vortices are observed to spread over the surface of the delta wing. Leeward side vortex breakdown location moves downstream of the delta wing and its trajectory slips towards the leading edge. Furthermore, variation of yaw angles, β are observed to have significant effects on the distribution of velocity components, turbulence statistics and distribution of pressure coefficients, Cp over the surface of the delta wing.