Re-Creating Waves in Large Currents for Tidal Energy Applications

Draycott, Samuel; Sutherland, Duncan; Steynor, Jeffrey; Sellar, Brian; Venugopal, Vengatesan

doi:10.3390/en10111838

Cited by 10 publications

(11 citation statements)

References 16 publications

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“…Refs. [4], [5], [6], for recent work assessing combined wave-current conditions). The location and types of instruments are detailed in Draycott et al.…”

Section: Experimental Design Materials and Methodsmentioning

confidence: 99%

Environmental & load data: 1:15 Scale tidal turbine subject to a variety of regular wave conditions

et al. 2019

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Experimental data was obtained in order to investigate the effect of waves on the loads and performance of tidal turbines. An instrumented 1:15 scale tidal turbine was installed in the FloWave Ocean Energy Research Facility, and a wide range of regular wave conditions were generated; systematically varying both wave frequency and height. Waves were generated both following and opposing a fixed mean current velocity of 0.81 m/s. Data are made available of the measured turbine loads and environmental conditions obtained for five repeats of 24 wave conditions via https://doi.org/10.7488/ds/2472 . A description of the data collection process, data processing, file structure and naming conventions are provided in this article. The analysis and presentation of the described dataset can be found in Ref. [1].

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“…Refs. [4], [5], [6], for recent work assessing combined wave-current conditions). The location and types of instruments are detailed in Draycott et al.…”

Section: Experimental Design Materials and Methodsmentioning

confidence: 99%

Environmental & load data: 1:15 Scale tidal turbine subject to a variety of regular wave conditions

et al. 2019

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“…Significant under-production of the energy content and large error in phase, highlighted by the mismatch in crest time, are observed. These effects are 13 due to wave-current interaction and in following-current conditions, this causes reduced amplitude and increased wave group velocity across all frequencies. The initial focusing ability is hampered by the frequency-dependent modification of wave phase.…”

Section: S(f )mentioning

confidence: 99%

“…A NewWave packet consists of a focused short-duration wave group generated from the design wave spectrum, thus giving a polychromatic test environment whilst avoiding the long test durations normally associated with extreme wave testing under irregular sea conditions [11]. The short time-frames provide a further advantage in the wave tank by ensuring wave reflections are not present [12], which may cause significant deviation from the desired and specified wave-induced velocity fields [13,14].…”

Section: Modelling Extreme Wave Loadsmentioning

confidence: 99%

Assessing extreme loads on a tidal turbine using focused wave groups in energetic currents

et al. 2019

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Tidal stream turbines are subject to large hydrodynamic loads, including those induced by extreme waves. Scale model testing in the laboratory plays an important role in ensuring that full scale tidal turbines are designed and operated in a manner that is appropriate for harsh ocean environments where waves and tidal currents coexist. For the first time, a fully-instrumented scaled tidal turbine is tested in short-duration focused wave groups representative of extreme environmental load cases expected at energetic tidal sites. In this paper, the subsequent variations in rotor-based loads, power and blade root bending moments are reported. These measurements are found to strongly follow the spectral and temporal form of the focused wave conditions, and peak loads and power output are found to exceed current-only values by 85% and 200% respectively. These rotor-averaged values display a high level of repeatability, demonstrating the suitability of focused waves for testing seabed-mounted tidal turbines. Extreme blade loads, which are dependent on angular position relative to wave phase, are captured through rapidly obtained repeat tests. New insight is subsequently gained into loading and response of tidal turbines in extreme sea conditions.

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“…This set-up is comparable to the taped underwater markers offered by Qualisys, but much lighter, water resistant and buoyant. A preliminary feasibility study showed that such a marker ball can be tracked by the Qualisys system whilst afloat on the surface and subject to wave motions in the University of Edinburgh's Curved Wave Tank [57] and in the FloWave basin, which has a diameter of 25 m and is also located at the University of Edinburgh [58][59][60][61][62][63]. For the experiments, 12 marker balls are added to the water in the circular tank ( Figure 1).…”

Section: Floating Infra-red Reflective Markersmentioning

confidence: 99%

“…Wave gauges are a very reliable and accurate measurement system to detect and record the motion of water free surfaces. They are standard measurement instruments in tank testing [64] and can also be used under very complex conditions [38,50,59,60,65] as well as near submerged structures [21,22,66,67]. This measurement system correlates the resistance between two parallel rods with the submerged water depth.…”

Section: Copper Tape Resistive Wave Gaugesmentioning

confidence: 99%

Capturing the Motion of the Free Surface of a Fluid Stored within a Floating Structure

Gabl

Steynor

Forehand

et al. 2018

Water

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Large floating structures, such as liquefied natural gas (LNG) ships, are subject to both internal and external fluid forces. The internal fluid forces may also be detrimental to a vessel’s stability and cause excessive loading regimes when sloshing occurs. Whilst it is relatively easy to measure the motion of external free surface with conventional measurement techniques, the sloshing of the internal free surface is more difficult to capture. The location of the internal free surface is normally extrapolated from measuring the pressure acting on the internal walls of the vessel. In order to understand better the loading mechanisms of sloshing internal fluids, a method of capturing the transient inner free surface motion with negligible affect on the response of the fluid or structure is required. In this paper two methods will be demonstrated for this purpose. The first approach uses resistive wave gauges made of copper tape to quantify the water run-up height on the walls of the structure. The second approach extends the conventional use of optical motion tracking to report the position of randomly distributed free floating markers on the internal water surface. The methods simultaneously report the position of the internal free surface with good agreement under static conditions, with absolute variation in the measured water level of around 4 mm. This new combined approach provides a map of the free surface elevation under transient conditions. The experimental error is shown to be acceptable (low mm-range), proving that these experimental techniques are robust free surface tracking methods in a range of situations.

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Re-Creating Waves in Large Currents for Tidal Energy Applications

Cited by 10 publications

References 16 publications

Environmental & load data: 1:15 Scale tidal turbine subject to a variety of regular wave conditions

Environmental & load data: 1:15 Scale tidal turbine subject to a variety of regular wave conditions

Assessing extreme loads on a tidal turbine using focused wave groups in energetic currents

Capturing the Motion of the Free Surface of a Fluid Stored within a Floating Structure

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