Modal Analysis of Strongly Coupled Fluid-Structure Interaction Problems

With recent trends in many energy markets, the use of hydroelectric turbines is shifting from base power delivery to grid regulators. The emergence of intermittent renewable energy sources is increasing the need for the use of turbines in off-peak conditions and frequent starts and stops. These cause transient phenomena that can be damageable to the fatigue life of the main turbine components. To tackle this issue, knowledge of the turbines vibration modes frequency and damping coefficient is essential. In this context, we developed a new modal analysis method for strongly coupled fluid-structure interaction (FSI) problems. The proposed technique couples linear elastic equations and linearized Navier-Stokes equations in a finite element formulation. This allows for the evaluation of the frequency and damping coefficient of the coupled modes of complex structures subject to important flows without the need for computationally heavy fully coupled non-linear time-integration FSI simulations. For now, a proof of concept has been elaborated using the 2D flag flutter problem and it was validated using 3D hydrofoil experiments.