Simulating variable pitch crossflow water turbines: A coupled unsteady ONERA-EDLIN model and streamtube model

• DOI: 10.1016/j.renene.2012.10.018
• Publication Date: 2012-11-23T02:33:32Z
• Authors: B. Paillard; F. Hauville; J.A. Astolfi
• Keywords: Stall (fluid mechanics); NACA airfoil

Abstract This article describes a new method for simulating unsteady hydrodynamics forces and moments on the blades of a crossflow ‘Darrieus’ turbine with active pitch variation. This method is based on the ONERA-EDLIN dynamic stall model, coupled with a momentum streamtube model to take into account the turbine interference on the flow. Both models are presented, and compared separately with experimental results for a pitching airfoil for the ONERA-EDLIN model; and for Darrieus turbine for the momentum theory. The model coupling is then detailed and compared with experimental data taken from the open literature [1] The turbine has 2 straight blades with a NACA 0012 section operating in water at a mean chord Reynolds number of 4 × 10 4 for tip speed ratio λ = 2.5, 5 and 7.5. Good agreement was found for average λ = 5, and qualitative agreement could be obtained at low and high λ , where dynamic stall effects and interference effects respectively are predominant. This is positive because λ = 5 is the closest value from the optimal power production point. Variable pitch is finally introduced in the model and several functions are tested in order to increase efficiency. A maximum increase of 53% on the power coefficient was found to occur with a sinusoidal law.