On the scaling of turbulence in a high Reynolds number tidal flow

Milne, Ian; Graham, J. M. R.; Coles, Daniel

doi:10.1017/jfm.2021.169

Cited by 4 publications

(1 citation statement)

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“…The vertical and streamwise model spectra were constructed using Equations ( 1) to (3), using measured values of mean velocity magnitude U and length scales L i where i = u, v, w. The measured vertical spectrum was computed directly from the measured vertical beam velocities. Given that the area under the spectrum represents the variance, we apply the variance method [39,40] to calculate the streamwise spectrum from the spectra measured by individual beams:…”

Section: Turbulence Spectrummentioning

confidence: 99%

How Applicable Are Turbulence Assumptions Used in the Tidal Energy Industry?

et al. 2023

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As tidal current and marine hydro-kinetic energy converters start to be deployed in pre-commercial arrays, it is critical that the design conditions are properly characterised. Turbulence is known to influence fatigue loads and power production, so developers use turbulence models to generate unsteady flows in order to simulate device performance. Most such models construct a synthetic flow field using a combination of measured parameters and theoretical assumptions. The majority in use today are based on atmospheric flow conditions and may have limited applicability in tidal environments. In the present work, we compare key turbulence model assumptions (which are recommended by the tidal turbine standards and are used in design software) to turbulence measurements from two tidal test sites in Scotland and Canada. Here, we show that the two sites have different levels of conformity to theoretical models, with significant variability within nearby locations at the same site. The agreement with spectral models is shown to be depth-dependent. The vertical component spectrum is better represented by the Kaimal model, while the streamwise spectrum is better represented by the von Kármán model. With the exception of one site, the shear profiles follow a power law, although with a different exponent to that commonly assumed. Both sites show significant deviations from the theoretical length scales and isotropy ratios. Such deviations are likely to misrepresent the loads experienced by a device. These results highlight the turbulence characteristics at real deployment sites, which are not well represented by current models, and, hence, which must be determined using field measurements.

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Section: Turbulence Spectrummentioning

confidence: 99%