NUMERICAL INVESTIGATION OF THE TRANSONIC BLADE-VORTEX INTERACTION

The transonic blade-vortex interaction is investigated numerically using a time accurate, high resolution Euler code based on a second-order Godunov-type method. Local mesh refinement is achieved by use of a hierarchical grid of structured embedded meshes. A two dimensional test case is presented which shows reasonably good agreement with the experimental results of Lee & Bershader for the head-on collision of a vortex and a NACA0012 aerofoil. Three limiting cases of the interaction are considered (i) 2D parallel interaction (ii) 3D perpendicular interaction between a streamwise vortex and a spanwise blade and (iii) 3D vortex cutting by a blade. For the parallel interaction noise generation is shown to involve a combination of vortex-blade vortex-shock interactions, which results in a complex system of pressure waves. The most distinctive aspects of this system are (i) propagation of a strong acoustic wave upstream of the leading edge and (ii) shock distortion and generation of waves on vortex-shock interaction. The near field flows of the three dimensional interactions are also examined. For both cases the sensitivity of transonic flows to velocity perturbations induced by the vortex is illustrated. Noise generating mechanisms of the vortex-cutting interaction are identified. Nomenclature