Effect of RBF interpolation parameters on the mesh motion and its application to high deflection flexible flaps

Multivariate interpolation by using radial basis functions (RBF) provides persuasive meshfree method for scattered data approximation. It offers a unified solution for mesh motion and fluid-structure interpolation problems. The method is computationally expensive in its pure form, therefore, it has been combined with a data reduction “double-edged greedy” algorithm to make it efficient for large degrees of freedom problems. This interpolation technique is equally efficient for all mesh types and has no dependency on the nature of the flow solver. In the present work RBF volume interpolation technique has been developed within a hybrid-unstructured mesh based Computational Fluid Dynamics (CFD) flow solver and has been applied to study the aerodynamic characteristics of high deflection flexible flaps. The choice of the interpolation parameters (the basis function and support radius) is important for accurate data interpolation. Different compactly supported basis functions have been tested for mesh deformation of DU-96-W-180 profiled wing flexible trailing edge. Based on the performance and computational efficiency, C2 function with compact support appears as the best choice. Additionally, study was conducted to evaluate the effects of varying the support radius. Large value of the support radius improves the interpolation accuracy but increase the computational time. The aerodynamic performance has been assessed by varying the flap deflection angle. The computed aerodynamic coefficients and the lift curve slope, for different flap angles, compares well with the available experimental data. RBF interpolation technique is robust and efficient in providing high quality deformed meshes. It updates the grid automatically and eliminates the need of new volume mesh generation for geometrical change.