Flutter analysis of turbomachinery cascades based on coupled CFD/CSD method

The paper presents a coupled method that combines a computational fluid dynamics (CFD) solver with a simplified structural motion equation in the time domain, and makes use of a hybrid multi-step scheme to investigate multi-passage cascade coupled flutter for turbomachinery. The method obtains the aeroelastic stability characteristics of the cascade by analyzing the dynamic responses of the blades. The aeroelastic characteristics of STCF-4 (Standard Test Configuration 4) are calculated with this method. The result for forecasting the instability district agrees well with that of the traditional uncoupled method, thus validating the coupled method. The method is applied to compute the free responses of cascades of different passages, and it is found that the turbomachinery flutter is different from wing flutter. Turbomachinery flutter is in many cases multimodal instability, and because the frequencies and damping coefficients of the instability mode are very close to each other, the time domain responses of the blades will typically show divergence in a gourd style.