Experimental investigations of the generation of vortical flows over bat-type double delta wing

Single or double delta wings with various sweep angles (Λ) are used in aircraft to provide further lift. The aerodynamic structure of bat-type non-slender and slender double-delta wing (DDW) with sweep angles (Λ), for example, 50°/64°, has not been adequately investigated in the literature. Due to this reason, the flow structure was experimentally investigated employing dye observations and particle imaging velocimetry (PIV). The flow structures of a bat-type DDW, immersed in free stream (U∞), were investigated at two specified end-view planes located at x/c = 0.6 and 0.8 with Re = 1 × 104. The angle of attack (α) of the wing relative to the free stream was varied between 10° and 35°. Using the dye visualization technique, the leading edge vortex collapse location was determined based on changes in α, and with the help of this qualitative observation, preliminary information about the vortical flow structures was obtained. The main part of this work involves capturing instantaneous velocity distributions within the flow field obtained by the PIV technique. This analysis provides information about the aerodynamics of the present wings. Spectral analysis was applied to the instantaneous velocity distribution to examine the velocity fluctuation to understand turbulent flow structures. The time-averaged streamline patterns, velocity vector distributions, time-averaged transverse and vertical velocity components, instantaneous and time-averaged vorticity patterns, Reynolds stress and kinetic energy distributions, and finally Strouhal numbers (St) were also determined to reveal the effects of wing geometry on the flow physics of a bat-type DDW.