ADVANCED INSTRUMENTATION FOR MEASURING FLUID-STRUCTURE COUPLING PHENOMENA IN THE GUIDE VANES CASCADE OF A PUMP-TURBINE SCALE MODEL

In the present study, the fluid-structure coupling is investigated in the guide vanes cascade of a pump-turbine scale model placed in the EPFL PF3 test rig. The paper focuses on the advanced instrumentation used to get reliable and complete fluid-structure coupling results. Semi-conductor strain gages are installed on three guide vanes which are especially weakened to account for stronger fluid-structure coupling phenomena. These are statically calibrated in terms of torsion torque and bending force. A laser vibrometer is used to measure the vibrating guide vane velocity Piezo-resistive pressure sensors are placed around the weakened guide vanes to monitor the influence of the structural vibrations on the surrounding flow. An underwater non-intrusive system is used to get an impulse excitation. The instrument set enables a reliable fluid-structure coupling investigation in hydraulic pump-turbine scale model. Finally, the results show a strong coupling between the vibrating guide vanes and the surrounding unsteady flow.