Overlap grid is usually used in numerical simulation of flow with complex geometry by high order finite difference scheme. It is difficult to generate overlap grid and the connectivity information between adjacent blocks, especially when interpolation is required for different type grids. The author proposed an interface flux reconstruction (IFR) method for numerical simulation using high order finite difference scheme with multi-block structured grids. Only one point was required to be overlapped between two connected blocks at the interfaces for this method. Although it was validated to be effective and accurate for inviscid and viscous problems with complex geometry, its error was two or three times larger than the coincident-point overlay method. In this study, a methodology similar with that taken by Huynh3 is utilized to improve the accuracy of the interface flux reconstruction method. Not only the flux at the point on the interface is corrected, the fluxes at the adjacent points of the interface are also reconstructed with a selected correction function. This improves the accuracy of the IFR method although the bias finite difference scheme is used to compute the spatial derivatives in the interior boundary region. Four problems are numerically solved with the developed code to validate the improved interface flux reconstruction method in this study. Four explicit schemes are used for spatial discretization, which are the 5-point and 9-point standard finite difference schemes, the 7-point and 11-point DRP schemes, respectively. Two dimensional pulse propagation in mean flow is computed with Cartesian mesh to validate the accuracy of the improved IFR method. It is found that the scheme coupled with the improved IFR method is the same precision or more accurate than it with point-coincident overlap method. Two dimensional pulse propagation in mean flow is also computed with wavy mesh, non-equal size mesh and skew mesh respectively to demonstrate the ability of the proposed method for non-uniform grid. The results also show that the improved IFR method is accurate. To demonstrate the ability of the proposed method for complex geometry, sound scattering by three cylinders is simulated and the numerical results compared with the analytical data. It is shown the numerical results agree well with the analytical data. The improved IFR method is applied to simulate viscous flow pass a cylinder at Reynolds number 150. The pressure coefficient on the cylinder surface, the lift and drag coefficients agree well with the data by other researcher. Finally the improved IFR method is utilized to simulate viscous flow over tandem airfoils at Reynolds number 10000 to show its capability for realistic viscous problem with complex geometry. The validations imply that the proposed improved IFR method is accurate and effective for inviscid and viscous problems with complex geometry.
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