Influence of turbulence on the drag of solid discs and turbine simulators in a water current

Blackmore, Tom; Batten, W.M.J.; Müller, Gerald; Bahaj, A.S.

doi:10.1007/s00348-013-1637-9

Cited by 21 publications

(25 citation statements)

References 14 publications

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“…Figure 2(b) shows the turbulence intensities behind both the small and large grids fit to a similar decay rate when the downstream distance is normalised by the grid bar width. The decay of turbulence intensity is consistent with previous studies [10]. The turbulence intensities are higher for the large grid as the normalised downstream distance is less than for the small grid.…”

Section: Turbulence Intensitysupporting

confidence: 91%

“…This is common practice in wind tunnel experiments [19] but not so in circulating water flumes. The experimental method used for this work is based on the previous work at a smaller scale in a gravity fed flume 2m wide and 0.6m deep [10]. Velocity shear is generated behind the grid bars producing vortices, which in turn break down to produce turbulence.…”

Section: Turbulence Generation Methodsmentioning

confidence: 99%

“…For example, it is possible to have 2 different flows with turbulence intensities of 10%, but one has large scale, low frequency turbulent structures, and the other with small scale, high frequency structures. Previous investigations have found the integral length scale to be an important parameter resulting in significant variations in thrust and wake recovery [10], [11].…”

Section: Turbulence Intensitymentioning

confidence: 99%

“…Tidal flows are highly turbulent with a broad range of length scales, and intensities [8], [9]. Previous investigations have shown how the thrust coefficient, or mean (time averaged) thrust force, of a porous disc rotor simulator can vary by over 20% in turbulent flows with different turbulence characteristics [10]. Further, numerical simulations have shown how turbulence affects the wake recovery behind an actuator disc turbine representation [11].…”

Section: Introductionmentioning

confidence: 99%

“…By changing the grid size the turbulence length scales can be changed, and by altering the distance downstream of the grid the turbulence intensity can be controlled as the turbulence is freely decaying [17]. This approach was first used by the authors in a series of small scale experiments in a gravity fed water flume using porous disc rotor simulators [10]. The same approach is used here using a large circulating water channel and a scale turbine in which we aim to consider the impacts of turbulence intensity and turbulence length scale on turbine performance and blade loads.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Effects of turbulence on tidal turbines: Implications to performance, blade loads, and condition monitoring

Blackmore

Myers

Bahaj

2016

International Journal of Marine Energy

Self Cite

126

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Laboratory scale testing of tidal turbines has generated valuable datasets to support optimised turbine design and numerical model validation. However, tidal sites are highly turbulent with a broad range of length scales and turbulence intensities that are site specific. In this work we describe an experimental campaign using static grids to generate turbulence and investigate its impact on a model tidal turbine in a circulating water flume. Length scales, energy spectra and turbulence dissipation rates are first considered for centre point measurements before full flow characterisation of the ambient conditions across the turbine rotor area. Six different cases were chosen to observe the performance of a 1/20 th scale 0.8m diameter turbine subjected to these flows. The rotor thrust and torque, and flapwise and edgewise blade root bending moments were measured. It was found that the thrust and power coefficients were sensitive to the estimate of ambient velocity. In the most extreme case the Betz limit could be 'exceeded' depending on which estimate of ambient velocity was used. Overall variations in the peak power coefficient of over 10% were observed, demonstrating the significance turbulence has on turbine performance. It was also found that there is a strong correlation between fluctuations in blade root bending moments and the rotor loads. As a result we proposed that fatigue loads acting on the blades may be estimated from the fluctuations in power output of the turbine. Therefore maintenance operations maybe optimised from real-time fatigue monitoring of blade loads without the need to install additional instrumentation on the turbine blades. Under this proposed regime the cost of energy will be reduced due to reductions in turbine costs and following optimisation of the maintenance requirements and operational costs. This could also improve turbine reliability which would have significant implications for large multi turbine arrays.

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Section: Turbulence Intensitysupporting

confidence: 91%

Section: Turbulence Generation Methodsmentioning

confidence: 99%

Section: Turbulence Intensitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Effects of turbulence on tidal turbines: Implications to performance, blade loads, and condition monitoring

Blackmore

Myers

Bahaj

2016

International Journal of Marine Energy

Self Cite

126

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Physical Modelling

Hann

Pérez-Collazo

2018

Wave and Tidal Energy

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Characterizing porous disk wakes in different turbulent inflow conditions with higher-order statistics

et al. 2023

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The wakes of a uniform and a non-uniform porous disk exposed to two different turbulent flows are investigated experimentally. The disks are representative of static wind turbine models found in literature. Six wake profiles were collected through hot-wire anemometry between three and 30 diameters downstream of the disks. Both one-point and two-point statistics are studied. The results show that higher freestream turbulence affects the wake of the uniform disk more than that of the non-uniform disk, also changing the wake’s shape and recovery rate. Furthermore, we confirm earlier findings that the turbulence at the centerline in the developed part of the wake is independent of both the design of the wake-generating object and the inflow. Similar to findings in the wake of a wind turbine, a ring of high intermittency is found at the very edge of the wakes of both disks and in both inflow conditions. We identify the existence of this ring over a range of scales. The results show that, even for higher-order two-point statistics, the developed wake of different porous disks qualitatively agrees well with the wake of wind turbine models. Graphical abstract

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Influence of turbulence on the drag of solid discs and turbine simulators in a water current

Cited by 21 publications

References 14 publications

Effects of turbulence on tidal turbines: Implications to performance, blade loads, and condition monitoring

Effects of turbulence on tidal turbines: Implications to performance, blade loads, and condition monitoring

Physical Modelling

Characterizing porous disk wakes in different turbulent inflow conditions with higher-order statistics

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