Experimental investigation of leading-edge vortex structure on delta wing models with different sweep angles

Single and double delta wings with different sweep angles (Λ) are employed in aircraft design to generate additional lift. In this study, the aerodynamic characteristics of a non-slender/slender bat-type double delta wing (DDW) with sweep angles of 50°/64° and a non-slender diamond-type delta wing (DW) with a sweep angle of 51° were investigated. Therefore, their flow structures were experimentally investigated using dye visualization and Particle Image Velocimetry (PIV) method. The flow structures of both models immersed in the free stream (U∞) were investigated at two end-view planes corresponding to x/c = 0.6 and 0.8 stations, as well as in the top-view plane, under Re = 10000 conditions. The angle of attack (α) of the wings were varied between 5° and 35°. Using the dye visualization technique, the collapse location of the leading-edge vortex (LEV) was identified as a function of α, and these provided preliminary insight into the vortical flow structures. The main part of the work focused on the analysis of velocity fluctuations obtained from instantaneous velocity fields measured by the PIV method in order to characterize turbulent flow structures. In addition, time-averaged velocity fields were evaluated. The results indicated that the breakdown of the LEVs on the bat-type DDW occurred farther downstream from the wing tip compared to the diamond-type DW. Consequently, it was concluded that the bat-type DDW has the potential to generate higher lift forces (FL), leading to improved maneuverability and enhanced flight performance.