Hybrid viscous/inviscid modelling of a hydrokinetic turbine performance

A computational study of hydrokinetic turbine hydrodynamics by using a hybrid viscous/inviscid-flow model is presented. The methodology integrates Detached Eddy Simulation for the numerical solution of the Navier-Stokes equations with a Boundary Integral Equation Model for potential flows. The formulation generalizes standard actuator disc models and provides a computationally efficient model to analyse the hydrodynamic performance and flowfield of single turbines and arrays in a viscous turbulent onset flow. An application of the hybrid DES/BIEM model to the analysis of the wake field downstream a horizontalaxis turine in uniform flow is presented. Numerical results for a five-bladed bi-directional turbine with elliptical blade sections are compared with experimental results including performance curves and a detailed characterization of the flowfield downstream the rotor using Particle Image Velocimetry. Results demonstrate the capability of the proposed methodology to correctly describe main flow features characterizing the turbine wake.