Fluid-Structure-Interaction in butterfly valves for hydropower: A numerical and experimental study

• The mean absolute error between CFD and experimental data is approximately 10%. • The experimentally compared CFD simulations allow for further optimization and reducing experimental investigations. • PIV is an appropriate fluid measurement technique to investigate butterfly valves. Light refraction must be compensated. • The 3D material VeroClear with Connex 350 printer (Stratasys, USA) can be used for flow investigation in a liquid environment. Butterfly valves are crucial in hydropower plants by controlling water flow in penstocks, requiring both streamlined geometries for minimal energy loss and high structural stiffness for emergency closure scenarios. Traditional design approaches often use static pressure loads, leading to conservative estimations and potential efficiency losses of up to 3%. This study presents a numerical investigation and experimental validation of the Fluid-Structure Interaction (FSI) of a butterfly valve, combining Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA). The focus of this work is experimental validation and numerical simulations for both the fluid flow and structural deformation within butterfly valves used in hydropower plants. The presented approach captures deformation due to FSI of a slender structure under hydraulic load with non-invasive methods, both DIC and PIV. Both one- and two-way coupled simulations were investigated. The numerical results are validated through 2D/2C Particle Image Velocimetry (PIV) measurements of the flow field and Digital Image Correlation (DIC) for non-invasive deformation analysis. A mean absolute error of approximately 10% between CFD and experimental data confirms the model’s reliability under operating conditions, while larger deviations at extreme angles highlight the limitations of 2D measurement techniques. The validated multi-physics simulation framework provides new insights into the deformation and stresses of bodies under flow conditions and vortex propagation effects in butterfly valves, but also the limitations that come with it.