Date on Master's Thesis/Doctoral Dissertation
Leading edges (Aerodynamics); Aerofoils
The perching maneuver of natural fliers is a complex motion involving fast change of angle of attack, complicated wing kinematics, large wing deformation and agile body motion control, but the prominent aerodynamic features can be revealed using a simple pitch-up wing motion coupled with a stream wise deceleration. In this dissertation the aerodynamic forces, the leading edge vorterx (LEV) development, and LEV circulation of pitch-up and perching wings are extensively studied at low Reynolds number conditions. 2D and 3D wings of different aspect ratios were linearly pitched up from 0 to 90 at three reduced pitch rates. The numerical investigation was conducted at a Reynolds number of 500 and the flow field was described using the unsteady three-dimensional incompressible Navier-Stokes equations on a set of composite overlapping grids. The Q-criterion was used to identify and isolate the LEV structure from shear layer vorticity. Results have shown that the LEV circulation depends primarily on the wing aspect ratio: increasing wing aspect ratio increased the rate of LEV circulation generation during the pitch-up motion. The reduced pitch rate for the pitch-up motion was found to delay the LEV circulation development when the aspect ratio was greater than two. For perching, pitch rate only altered the LEV propagation away from the wing, and not the magnitude of the circulation.
Hord, Kyle, "Numerical study of leading edge vortex circulation development on finite aspect ratio perching wings." (2014). Electronic Theses and Dissertations. Paper 633.