On the spectral behaviour of the turbulence-driven power fluctuations of horizontal-axis turbines. (10th December 2020)

• Record Type: Journal Article
• Authors: Deskos, Georgios; Payne, Grégory S.; Gaurier, Benoît; Graham, Michael
• Is Part Of: Journal of fluid mechanics. Volume 904(2020)
• Publication Date: 2020-12-10
• Subjects: flow–structure interactions; Fluid mechanics -- Periodicals; 532.005
• DOI: 10.1017/jfm.2020.681
• Languages: English
• ISSNs: 0022-1120

Abstract

Abstract: Abstract : In this article we consider the spectral behaviour of turbulence-driven power fluctuations for a single horizontal-axis turbine. To this end, a small-scale instrumented axial-flow hydrokinetic turbine model ( $\textrm {diameter}=0.724\ \textrm {m}$ ) is deployed in the long water flume situated in the laboratory facilities of IFREMER in Boulogne-sur-Mer, France, and synchronous measurements of the upstream velocity and the rotor are collected for different tip-speed ratios. The study confirms previous findings suggesting that the power spectra follow the velocity spectra behaviour in the large scales region and a steeper power law slope behaviour ( $-11/3$ ) over the inertial frequency sub-range. However, we show that both the amplitude of the power spectra and low-pass filtering effect over the inertial sub-range also depend on the rotor aero/hydrodynamics (e.g. $\mathrm {d}C_L/\mathrm {d}\alpha$ ) and the approaching flow deceleration and not solely on the rotational effects. In addition, we present a novel semi-analytical model to predict the dominant blade-passing frequency harmonics in the high-frequency regime using the rotationally sampled spectra technique. For all calculations, the distortion of incoming turbulence is taken into account.