Manipulation of Leading-Edge Separation Zone through Spanwise Segmentation

Abstract

Experimental studies have been made on a three-dimensional separation zone at the segmented leading of a long blunt plate with right-angled corners. The leading edge is periodically segmented into a isosceles triangle with the apex angle e being changed from 180° to 60° with an interval of 30°. Surface flow patterns are presented and interpreted by nodes and saddles of the skin-friction vector field and by reattachment and separation lines. Distributions of time-mean and root-mean-square pressures on the surface are also discussed in terms of these singularities and the characteristic lines. The longitudinal extent of the separation zone defined as the distance between an apex and the most downstream reattachment saddle is less than that of the two-dimensional separation zone (θ=180°). The separation zone is dominated by spanwise large-scale vortices when e is more than a critical value θ_c(≒100°) and by longitudinal vortices when θ<θ_c Finally, the frequency at which the large-scale vortices are shed from the separation zone is found to increase with decreasing apex angle.