FSI: Water Turbine

FSI Method for Water Turbine CFD Simulation in ANSYS Fluent

Introduction

This study investigates the water flow around a vertical water turbine using an unsteady, transient CFD simulation in ANSYS Fluent. The turbine blades are assumed to be affected by the passing fluid flow, such that the fluid impedes forces on the turbine body, causing deformation and resizing of the blade structure. Since the problem involves the simultaneous solution of both fluid and solid domains, a Fluid-Structure Interaction (FSI) approach is employed, coupling the fluid flow solution with a Transient Structural analysis through system coupling. The simulation is solved using a pressure-based, transient solver, with gravitational effects neglected.

Geometry and Mesh

The three-dimensional model was designed in Design Modeler, consisting of a large cubic fluid domain with the water turbine positioned inside as the solid domain. The domain was discretized using an unstructured mesh generated in ANSYS Meshing, resulting in a total element count of 523,202.

Methodology

Turbulent flow behavior was resolved using the standard k-epsilon viscous model with standard wall functions applied for near-wall treatment. The dynamic mesh approach, incorporating smoothing and remeshing methods, was coupled with a system coupling dynamic mesh zone to capture the two-way interaction between the fluid flow and the deforming turbine structure. At the inlet, a velocity-inlet boundary condition was applied with a velocity magnitude of 1.5 m/s, while a pressure-outlet condition with 0 Pa gauge pressure was set at the outlet. The turbine blades and fixed surfaces were defined as stationary walls. The SIMPLE algorithm was used for pressure-velocity coupling, with second-order upwind discretization applied to pressure and momentum, and first-order upwind discretization applied to turbulent kinetic energy and turbulent dissipation rate. The simulation was initialized using the standard initialization method with an x-velocity of 1.5 m/s.

Results and Conclusion

The coupled FSI solution captures the dynamic interaction between the water flow and the turbine blade structure, allowing the deformation behavior of the blades under fluid loading to be evaluated alongside the surrounding flow field characteristics, providing insight into the structural response of the turbine under realistic unsteady hydrodynamic conditions.