A three-dimensional Navier-Stokes solver based upon a high resolution shock-capturing scheme has been developed in order to analyze complex flow phenomena inside transonic fan/compressor rotors, especially tip clearance flow. The aim of this research is to find out a key element concerned with aerodynamic instability of transonic fan/compressor rotors such as rotating stall and surge by using this newly developed numerical tool. The numerical analysis of this research is twofold. First it investigates the flowfield of a transonic compressor rotor along the design speed operating line. It obtains definite flow structures around the tip region and clear description of the transition of the flow pattern inside the clearance gap between operating points, which shows that shock-tip leakage vortex interaction plays an important role on both loss generation and the failure of steady flow, or surge. A model will be proposed on the onset of tip stall in transonic compressor rotors according to the calculated results.
Secondly, the above model will be examined through a series of numerical experiments by altering tip clearance height white keeping the design speed. From qualitative point of view, the model works fairly well and seems geometry-independent for typical transonic fan/compressor rotors. A clue to the optimum clearance is also obtained.