Browsing by Author "Snyder, Richard D."
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- Deterministic Global Optimization of Flapping Wing Motion for Micro Air VehiclesGhommem, Mehdi; Hajj, Muhammad R.; Watson, Layne T.; Mook, Dean T.; Snyder, Richard D.; Beran, Philip S. (Department of Computer Science, Virginia Polytechnic Institute & State University, 2010-12-01)The kinematics of a flapping plate is optimized by combining the unsteady vortex lattice method with a deterministic global optimization algorithm. The design parameters are the amplitudes, the mean values, the frequencies, and the phase angles of the flapping motion. The results suggest that imposing a delay between the different oscillatory motions and controlling the way through which the wing rotates at the end of each half stroke would enhance the lift generation. The use of a general unsteady numerical aerodynamic model (UVLM) and the implementation of a deterministic global optimization algorithm provide guidance and a baseline for future efforts to identify optimal stroke trajectories for micro air vehicles with higher fidelity models.
- Shape and Structural Optimization of Flapping WingsStewart, Eric C. (Virginia Tech, 2014-01-11)This dissertation presents shape and structural optimization studies on flapping wings for micro air vehicles. The design space of the optimization includes the wing planform and the structural properties that are relevant to the wing model being analyzed. The planform design is parameterized using a novel technique called modified Zimmerman, which extends the concept of Zimmerman planforms to include four ellipses rather than two. Three wing types are considered: rigid, plate-like deformable, and membrane. The rigid wing requires no structural design variables. The structural design variables for the plate-like wing are the thickness distribution polynomial coefficients. The structural variables for the membrane wing control the in-plane distributed forces which modulate the structural deformation of the wing. The rigid wing optimization is performed using the modified Zimmerman method to describe the wing. A quasi-steady aerodynamics model is used to calculate the thrust and input power required during the flapping cycle. An assumed inflow model is derived based on lifting-line theory and is used to better approximate the effects of the induced drag on the wing. A multi-objective optimization approach is used since more than one aspect is considered in flapping wing design. The the epsilon-constraint approach is used to calculate the Pareto optimal solutions that maximize the cycle-average thrust while minimizing the peak input power and the wing mass. An aeroelastic model is derived to calculate the aerodynamic performance and the structural response of the deformable wings. A linearized unsteady vortex lattice method is tightly coupled to a linear finite element model. The model is cost effective and the steady-state solution is solved by inverting a matrix. The aeroelastic model is used to maximize the thrust produced over one flapping cycle while minimizing the input power.