Three-Bladed Horizontal Axis Water Turbine Simulations with Free Surface Effects

Abstract

The water level above a hydrokinetic turbine is likely to vary throughout the season and even along the day. In this work, the influence of the free surface on the performance of a three bladed horizontal-axis turbine is explored by means of a three-dimensional, transient, two-phase flow computational model implemented in the commercial CFD software ANSYS Fluent 19.0. The k – ω SST Transition turbulence model coupled with the Volume of Fluid (VOF) method is used to track the air-water interface. The rotor diameter is D = 0 8m. Two operating conditions are analyzed: deep tip immersion (0.55D) and shallow tip immersion (0.19D). Three tip speed ratios are evaluated for each immersion. Simulation results show a good agreement with experimental data reported in the literature, although the computed torque and thrust coefficients are slightly underestimated. Details of the free surface dynamics, the flow past the turbine and the wake near the rotor are also discussed.

Systematic Review of Computational Fluid Dynamics Modelling and Simulation Techniques Employed in Vertical Axis Hydrokinetic Turbines

“…Furthermore, Rodríguez et al, showed that ANSYS-Fluent software, which is a commercially available CFD tool, use VOF model to accurately monitor the interface between air and water. Additionally, the unstable Reynolds-averaged Navier-Stokes (URANS) SST k-ω and Transition SST turbulence models are utilised to calculate the unsteady flow field [40]. Rubio-Clemente et al, also provided that the numerical simulation accuracy was improved by utilizing ANSYS Fluent software, which incorporated a 6-DoF user-defined function and URANS equations.…”

Numerical Investigation of the Performance, Hydrodynamics, and Free-Surface Effects in Unsteady Flow of a Horizontal Axis Hydrokinetic Turbine

“…Rodriguez et al [23] performed two-phase flow simulations of the HAHT rotor described in Bahaj et al [17], for two blade tip immersions and three TSRs. The computational approach incorporated a transition four-equation turbulence model, the Volume of Fluid (VOF) method for interface tracking, and the sliding-mesh technique to account for blade rotation.…”