Predictions of the Hydrodynamic Performance of Horizontal Axis Marine Current Turbines

What is it about?

The marine current turbine is the mechanical device that captures the kinetic energy of marine current to generate electrical power. This paper presents the application of an academic panel code based on potential flow theory for the analysis of marine current turbines. The aim of this work is also to analyze the effect of the addition of a duct on the hydrodynamic performance of the turbine. The numerical results show that the addition of duct improves significantly the efficiency of the turbine.

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Why is it important?

An academic panel code based on potential flow theory has been used to assess the hydrodynamic performance of a marine current turbine with and without a duct. The numerical results for the bare turbine have been compared with the experimental results reported in reference [6]. Although the trend is the same, the numerical results present significantly lower values for the power coefficient. Baltazar and Falcao de Campos [8] obtained the same results with a very similar method and they propose to correct the section drag to account for flow separation. From the spanwise distribution of sections angles, it appears that flow separation must occur even for configurations with high power coefficient values. Flow separation and cavitation being closely linked, serious investigation has to be carried out to decide whether it is advisable to design a water turbine presenting flow separation even in normal operational mode. Simulations with a Navier-Stokes solver are needed as long as the turbulence model is capable of predicting the correct hydrodynamic forces in presence of flow separation which is known to be a challenging problem. Experimental results with flow separation monitoring are also needed. In the course of our study, we questioned the upper limit given by the GGS model [2] which is half the Betz limit. We found that the GGS model is based on a wrong assumption and serious contradiction are embedded in the proof. Surprisingly the paper has been cited more than a hundred times and only one author suspected something was wrong and no one investigated any further. Marine Current Turbines, Panel Method, Boundary Element Method, Turbine Design, Performances Predictions, Ducted turbine.

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