Abstract: Combined CFD flow analysis, stiffness and stre- ngth software, the flow is analyzed under different operation condition of Francis turbine. Through the program parameters are transferred to the structure analysis software, then for the deformed blade the grid is partitioned and the flow field is co- mputed, and the stress and strain of blade of Francis turbine are obtained, finally the Fluid field distribution under deformed turbine blade is analyzed in detail, which reaches the actual Fluid-solid coupling. The research result shows that the maxi- mal stress occurs at the joint of outlet of blade and crown, where stress concentrates seriously, and the tired destroy is prone to occur. The most deformation occurs at the joint of outlet of blade and band, the deformation increases gradually from crown to band, which is the sensitivity area of vibration. The influence of deformed blade on inter flow field represents that the press increases at the head of inlet of blade, the flow velocity increases and press decreases at the outlet of blade near band, then the cavitation performance is fallen. The defor- med blade causes the vortex in the draft tube, turbulence seve- rity, which explains that the influence of deformed blade on inter flow field is the real reason of causing crack and vibration of turbine.

Key words: Blade deformation, Draft tube vortex, Fluid-solid coupling, Francis turbine runner, Part load