Modal analysis of Francis turbine blade based on fluid-structure interaction theorem

The paper deals with the modal analysis of Francis turbine blade with fluid-structure interaction (FSI). The dynamic equation of Francis turbine blade in air and operating flow path is studied, and two different governing equations are solved together. Then the mathematic model for vibration and stress analysis was built to calculate the natural frequency in air by using finite element analysis (FEA). In addition, the blade's coupled modelling in operating flow path lies on a classical finite element discretisation of the coupled fluid-structure equation. According to the analysis of results, the influential coefficients by the FEA adopted in the present study are in fairly good agreement with the experienced data listed in some documents. The modal analysis of the blade highlights that the natural frequencies decrease dramatically and the mode shapes in operating flow path are close to those in air. So the method presented herein can be used efficiently as a reliable tool for the fatigue reliability design and performance analysis of Francis turbine blade.