Numerical Simulation Of Flapping-wing Flow Field Using The DFD Method

Flapping-wing flow at low Reynolds numbers has been investigated by the local domain-freediscretization (DFD) method. In the DFD method, the discrete form of governing equations caninvolve the points inside and outside the solution domain. The functional values at the exteriordependent points can be obtained by interpolation or solving the local simplified equations, and at thesame time the solid boundary conditions are imposed. Moving-boundary flows can be simulated on afixed grid, and there is no need to update the grid to follow the motion or deformation of a body.Spatial discretization is complished by the finite volume Galerkin approximation, and the dual-timestpepping scheme is used in temporal disccretization.The numerical experiments and applications consist of four parts:(1) Flow induced by a sphererotating at constant angular velocity in an unbounded incompressible fluid at rest. This test verifiesthe reliability of the local DFD method.(2) Flapping-wing flow past wing-wing model. Comparisonsbetween the computed results and the referenced data further confirm the reliability of local DFD forcomplex moving-boundary problems. High-lift mechanisms reflected in the periodic variation of liftand drag and the influence of flapping modes on aerodynamic forces are investigated.(3)Flapping-wing flow past wing-body model. Vortex structures and flight mechanisms are analyzed.(4)Flow past a micro-air-vehicle with flexible flapping-wings. The influences of flow parameters on theaerodynamic forces and the flow structures under various advance ratios are studied.Applications to flapping-wing flow simulations have demonstrated the natural advantage of thelocal DFD method in dealing with complex moving-boundary problems. Results of this paper havecertain significances in insect aerodynamics study and FMAV design.