Characterisation of current and turbulence in the FloWave Ocean Energy Research Facility

Sutherland, Duncan; Noble, Donald R.; Steynor, Jeffrey; Davey, Thomas; Bruce, Tom

doi:10.1016/j.oceaneng.2017.02.028

Cited by 31 publications

(32 citation statements)

References 13 publications

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“…These enable the creation of a predominantly straight flow in any direction across the central test area [20], where waves can also be added to the current field at any relative angle. A detailed drawing of the wave and current generation systems can be found in Sutherland et al [13]. The nature of creating straight flow in a circular basin means that there is some inherent spatial variability [20].…”

Section: The Flowave Ocean Energy Research Facilitymentioning

confidence: 99%

“…It is worth mentioning that there is no control over turbulence metrics or vertical profiles at the facility, and as such, only mean bulk flow is emulated. Turbulence Intensities (TI) at FloWave are typically between 5 and 10% [13]. For the three velocities used, 0.25, 0.38 and 0.51 m/s, the depth averaged TI values are 8.3%, 7.1% and 7.0%, respectively.…”

Section: Test Planmentioning

confidence: 99%

“…For the three velocities used, 0.25, 0.38 and 0.51 m/s, the depth averaged TI values are 8.3%, 7.1% and 7.0%, respectively. Further specifics of the ADV analysis procedure, along with baseline (no waves) velocity and turbulence measurements, are given in detail in Sutherland et al [13].…”

Section: Test Planmentioning

confidence: 99%

“…To ensure the correct current velocity, previous depth averaged calibrations have been used to set tank flow-generation motor RPM (as presented in [13]). These were verified with the ADV in situ to ensure that they were still valid at the measurement location.…”

Section: Corrected Irregular Sea Statesmentioning

confidence: 99%

“…This paper therefore explores the re-creation of combined wave-current conditions at scale for tank testing physical models of TSTs, with the focus on isolating and predicting the effect of wave reflections on the flow field. Baseline flow and turbulence are not focussed on, as this is well described in Sutherland et al [13]. Namely, this paper details:…”

Section: Introductionmentioning

confidence: 99%

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Re-Creating Waves in Large Currents for Tidal Energy Applications

et al. 2017

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Unsteady wave loading on tidal turbines impacts significantly the design, and expected life-time, of turbine blades and other key components. Model-scale testing of tidal turbines in the wave-current environment can provide vital understanding by emulating real-world load cases; however, to reduce uncertainty, it is important to isolate laboratory-specific artefacts from real-world behaviour. In this paper, a variety of realistic combined current-wave scenarios is re-created at the FloWave basin, where the main objective is to understand the characteristics of testing in a combined wave-current environment and assess whether wave effects on the flow field can be predicted. Here, we show that a combination of linear wave-current theory and frequency-domain reflection analysis can be used to effectively predict wave-induced particle velocities and identify velocity components that are experimental artefacts. Load-specific mechanisms present in real-world conditions can therefore be isolated, and equivalent full-scale load cases can be estimated with greater confidence. At higher flow speeds, a divergence from the theory presented is observed due to turbulence-induced non-stationarity. The methodology and results presented increase learning about the wave-current testing environment and provide analysis tools able to improve test outputs and conclusions from scale model testing.

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Section: The Flowave Ocean Energy Research Facilitymentioning

confidence: 99%

Section: Test Planmentioning

confidence: 99%

Section: Test Planmentioning

confidence: 99%

Section: Corrected Irregular Sea Statesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Re-Creating Waves in Large Currents for Tidal Energy Applications

et al. 2017

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Experimental assessment of tidal turbine loading from irregular waves over a tidal cycle

Draycott

Steynor

Nambiar

et al. 2019

J. Ocean Eng. Mar. Energy

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Waves interact with currents in tidal channels with the resulting wave-current environment largely determining the loads experienced by tidal stream turbines. Over a tidal cycle, the magnitude and direction of the current velocity changes and hence so does the combined wave-current conditions the turbines must operate within. Here we demonstrate this effect experimentally, generating a realistic irregular wave case in both following (in the same direction as the waves) and opposing currents prior to assessing the resulting loads on a fully instrumented 1:15 scale tidal turbine model aligned with the current direction. Large changes in the environmental conditions, along with the turbine performance and loads, are demonstrated through the presentation of temporal, spectral and statistical outputs. The experimental results demonstrate that the full-scale equivalent significant wave height changes from 2.25 m in zero current to 6.11 m in 3.2 m/s opposing current and 1.56 m in 3.2m/s following current. The corresponding standard deviations of measured turbine parameters for the opposing condition range between 215 and 260% of the following case, and between 340 and 565% of the current-only measurements. Hence, when waves are present, significantly greater fatigue damage will be accumulated during one-half of the tidal cycle. The mean values, however, appear to be unaffected by the presence of waves suggesting that the overall turbine performance is unaltered. These results demonstrate the requirement to understand the combined wave-current environment and to test and de-risk tidal stream turbines for operation in both following and opposing wave-current conditions. Significant additional insight is gained into the nature of loads experienced by tidal turbines in irregular wave conditions, a scarcely documented phenomenon.

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