Numerical Simulation of a Low-head Axial Flow Microturbine Considering Cavitation and Sediment Flow

This article presents a numerical investigation of cavitation and sediment-induced erosion phenomena in an ultra-low-head axial hydraulic turbine designed to operate at a head of ۴ m for small-scale applications. Computational Fluid Dynamics (CFD) simulations were used to assess the turbine’s hydraulic performance and to map regions of cavitation and erosive wear on its components. The simulations were performed using ANSYS CFX. The operating conditions and performance data used in the model were based on experimental results, which enabled validation of the numerical model. The turbine geometry was reconstructed from aerodynamic profiles and assembled in cylindrical coordinates. A three-dimensional mesh was generated for the different domains, with appropriate refinement in regions of high gradients to ensure mesh independence. In the simulations, the SST k-ω turbulence model was employed, with cavitation modeled using the Rayleigh–Plesset equation and Lagrangian tracking of solid particles to estimate erosion via the Finnie model. The particle dynamics analysis revealed a Stokes number much smaller than unity, indicating a high degree of hydrodynamic coupling where particles closely follow the fluid streamlines. The numerical results showed good agreement with the turbine’s experimental characteristic curves, validating the proposed model. The results indicated that vapor cavities formed preferentially on the suction side of the rotor blades, whereas particle-induced erosion was concentrated on the pressure side of the blades and on the casing walls. The analysis demonstrated that the simultaneous action of cavitation and sediment particles intensifies the damage mechanisms, accelerating surface wear and reducing the turbine’s service life.

کلیدواژه ها:

Sediment erosion ، Cavitating flow ، Rayleigh&ndash ، Plesset equation ، Discrete phase model ، Finnie erosion model