Tag Archives: Wave-Current Interaction

The effect of surface waves on the performance characteristics of a model tidal turbine


L. Luznik, K.A. Flack, E.E. Lust, and K. Taylor – Renewable Energy, November, 2013

Abstract

Scale model tests were conducted on a three bladed horizontal axis tidal turbine in a large tow tank facility at the United States Naval Academy. Performance characteristics are presented for a turbine towed at a constant carriage speed for cases with and without surface waves. Intermediate waves were modeled that are representative of swells typically found on the continental shelf of the United States eastern seaboard. The oscillatory wave velocity present in the water column results in significant variations in measured turbine torque and rotational speed as a function of wave phase. This in turn produces cyclic variations in tip speed ratio and power coefficient. The power coefficient over the entire wave phase did not show a difference from the experiments without waves for a range of tip speed ratios, as reported in previous studies. The waves limited the lower range of tip speed ratios at which the turbine could operate. These results highlight the impact of surface waves on turbine design and performance, and the importance of understanding the site-specific wave conditions.

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Flume tank characterization of marine current turbine blade behaviour under current and wave loading


B. Gaurier, P. Davies, A. Deuff, G. Germain – Renewable Energy, November, 2013

Abstract

The long term reliability of tidal turbines is critical if these structures are to be cost-effective. Optimized design requires a combination of material durability models and structural analyses which must be based on realistic loading conditions.

This paper presents results from a series of flume tank measurements on strain gauged scaled turbine blades, aimed at studying these conditions. A detailed series of tests on a 3-blade horizontal axis turbine with 400 mm long blades is presented. The influence of both current and wave-current interactions on measured strains is studied. These tests show that wave-current interactions can cause large additional loading amplitudes compared to currents alone, which must be considered in the fatigue analysis of these systems.

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Filed under Component Development, Experiments