Stall flutter computation of turbomachinery blade based on a CFD/CSD coupling method

A computational fluid dynamics/computational structural dynamics (CFD/CSD) model coupling in the time domain is developed for the stall flutter computation of turbomachinery blade. CFD and CSD slovers are coupled via successive iterations within each physical time step. In CFD analysis, a robust scheme named AUSM+-UP is adopted and delayed-detached-eddy simulation (DDES) is applied to simulating separated flow. In the structure analysis, the structural dynamic equation of rotating blade is constructed based on a modal approach and a hybrid multi-step scheme is used to solve the equation. The CFD codes calculate flow field characteristics of Rotor37 under different working conditions. The computed results show good agreement with the experimental results, both in overall performance and flow field details. The presented method is then applied to flutter computation and analysis of a test compressor rotor. The computed time response of generalized coordinates successfully predicts stall flutter at near stall condition and shows it to be a phenomenon of single bending-modal divergence and modal uncoupling. The results also indicate that the flow unstability and unsteadiness are key factors affecting the flutter characteristics. Besides, it is found that for the stable blade, the decrease of reduced frequency may cause stall flutter. ©, 2015, AAAS Press of Chinese Society of Aeronautics and Astronautics. All right reserved.