Numerical simulation of 3d flapping wing based on chimera method

The aerodynamic characteristics of flapping wing are investigated by solving the 3D Euler/Navier-Stokes equations based on the chimera method. The spatial discretization is characterized by a second-order cell-center method for finite volumes. A five-stage Runge- Kutta scheme is employed to achieve convergence of the solution by integration with respect to time. For unsteady flows an implicit dual time-stepping scheme is used. Implicit residual smoothing is employed to accelerate convergence. The Baldwin-Lomax algebraic turbulent model is applied for calculating the turbulence flows. The grid system is based on the chimera method which includes the motion wing grid and stationary background grid. Chimera grid is chosen for it's easy to deal with complex configuration and moving bodies. Besides, an efficient method, namely distancedecreasing searching method, is developed to apply on the hole-cutting and the interpolation cells searching of chimera grid preprocessing. Based on these numerical methods, comparison between the results of Euler and Reynolds Average Navier-Stokes (RANS) equations is given. Then, the effect of reduced frequency, angle of attack, flapping angle, twisting angle, and airfoil of cross section are researched. The result shows that the lift and thrust coefficients get by RANS is lower than the Euler equations because of viscosity. And the result accord with the actual situation logically. The increasing of angle of attack can increase the lift coefficient, but decrease the thrust coefficient. The increasing of reduce frequency can increase the thrust coefficient, but affect average lift coefficient slightly, just increase the peak value range of lift coefficient. The increasing of flapping angle affects the lift and thrust coefficient similarly as the increasing reduced frequency. The increasing of twisting angle can decrease the peak value range of lift coefficient and decrease the thrust coefficient at the condition of Φ=90°. The airfoil thickness has little effect on lift coefficient, but has obvious effect on thrust coefficients. The relationship between airfoil thickness and thrust coefficient is not monotony. Too thin or too thick airfoils both can not get big thrust coefficient. The authors confirm that they, and/or their company or institution, hold copyright on all of the original material included in their paper. They also confirm they have obtained permission, from the copyright holder of any third party material included in their paper, to publish it as part of their paper. The authors grant full permission for the publication and distribution of their paper as part of the ICAS2008 proceedings or as individual off-prints from the proceedings.