A NONLINEAR AEROELASTICITY ANALYSIS OF A FAN BLADE USING UNSTRUCTUREDDYNAMIC MESHES

The main objective of this paper is to present a methodology for the t hree-dimensional aeroelasticity analysis of turbomachinery blades usin g an unstructured compressible Navier-Stokes solver for the fluid and a modal model for the structure. The basic fluid solver is constructed in the form of a central difference scheme with explicitly added arti ficial dissipation which is based upon the fourth- and second-order di fferences of the solution. The temporal discretization uses an implici t time integration scheme based on a Jacobi relaxation procedure. The structural modes of vibration are determined via a finite element mode l and the mode shapes are interpolated on to the fluid mesh in a manne r that is consistent with general unstructured tetrahedral grids. A sp ring analogy algorithm that can move the mesh according to the instant aneous shape of a deforming blade has been developed for the accurate hacking of the solid boundaries without creating excessive grid distor tions. The performance of the resulting system was examined by conside ring the aeroelastic behaviour of NASA Rotor 67 fan blade and predicti ons were compared to experimental results wherever possible. Using a t hree-dimensional cyclic symmetry model, the tip leading edge time hist ories were predicted under peak-efficiency and near-stall conditions, and the corresponding aeroelastic natural frequencies and aerodynamic damping values were determined. The blade was found to be stable in al l cases considered.