Numerical study of flapping wing air vehicle based on chimera grid

A method is developed to investigate the aerodynamic characteristics of flapping wing air vehicle by solving the 3D Navier-Stokes equations based on the chimera grid. 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 grids which are composed of the motion wing grid and stationary background grid. The background grid includes fuselage, vertical and horizontal stabilizers. An efficient method, namely distance-decreasing searching method, is developed to apply on the hole-cutting and the interpolation cells searching of chimera grid preprocessing. Based on these numerical methods, the aerodynamic characteristics of flapping wing air vehicle can be researched. The numerical result shows that the flapping wing generates the main part of lift force and all the thrust force. The existence of fuselage can increase the drag force or decrease the thrust force. This solver can be used to investigate the layout of parts so it is practical in researching and designing of flapping wing air vehicle.