Leading Edge Vortex Circulation Development on Finite Aspect Ratio Pitch-Up Wings

摘要

We study the leading edge vortex (LEV) development and LEV circulation of pitch-up wings at a low Reynolds number of 500. Wings of different aspect ratios are linearly pitched up from 0 to 90 deg at two reduced pitch rates of 0.1 and 0.2. The flowfield is described by solving the unsteady three-dimensional incompressible Navier-Stokes equations on composite overlapping grids. The Q-criterion is used to isolate the LEV structure from shear layer. The simulation shows that forces increase with the aspect ratio and the pitch rate. The stall angle increases with the pitch rate but decreases with the aspect ratio. also It is shown that the LEV circulation depends on the wing aspect ratio: increasing wing aspect ratio increases the rate of LEV circulation generation during the pitch-up motion. It also shows that the reduced pitch rate could delay the LEV circulation development. Furthermore, the study shows that the LEV circulation distribution better matches the spanwise force distribution for higher aspect ratio wings.