Evaluation of the swirl characteristics of a tidal stream turbine wake

Morris, Ceri; O'Doherty, Daphne Maria; Mason-Jones, Allan; O'Doherty, Timothy

doi:10.1016/j.ijome.2015.08.001

Cited by 26 publications

(21 citation statements)

References 10 publications

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“…Thus, measurements were performed for λ close to the freewheeling region. Morris et al [46] reported that swirl in the wake reaches its maximum value at λ P and decreases both for lower and higher values of λ. Higher swirl is expected to enhance displacement, shear layer growth, flow entrainment, etc., of the wake [47]; thus, the wake at λ = 6.15 is expected to be less complex than that at λ P .…”

Section: Experimental Datamentioning

confidence: 99%

Validation of Tidal Stream Turbine Wake Predictions and Analysis of Wake Recovery Mechanism

Salunkhe

Fajri

O'Doherty

et al. 2019

JMSE

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This paper documents the predictive capability of rotating blade-resolved unsteady Reynolds averaged Navier-Stokes (URANS) and Improved Delayed Detached Eddy Simulation (IDDES) computations for tidal stream turbine performance and intermediate wake characteristics. Ansys/Fluent and OpenFOAM simulations are performed using mixed-cell, unstructured grids consisting of up to 11 million cells. The thrust, power and intermediate wake predictions compare reasonably well within 10% of the experimental data. For the wake predictions, OpenFOAM performs better than Ansys/Fluent, and IDDES better than URANS when the resolved turbulence is triggered. The primary limitation of the simulations is under prediction of the wake diffusion towards the turbine axis, which in return is related to the prediction of turbulence in the tip-vortex shear layer. The shear-layer involves anisotropic turbulent structures; thus, hybrid RANS/LES models, such as IDDES, are preferred over URANS. Unfortunately, IDDES fails to accurately predict the resolved turbulence in the near-wake region due to the modeled stress depletion issue.

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Section: Experimental Datamentioning

confidence: 99%

Validation of Tidal Stream Turbine Wake Predictions and Analysis of Wake Recovery Mechanism

Salunkhe

Fajri

O'Doherty

et al. 2019

JMSE

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“…The instrument was set to a sampling frequency of 50Hz [24] and a sampling volume of 1.7×10 -7 m 3 . The time traces obtained from the experiments were filtered using the phase space thresholding (PST) technique described in Goring and Nikora [44] to eliminate spikes and ensure quality data are computed as follows (6) with N being the total number of samples, T the corresponding total sampling period and R(dt) the autocovariance defined as…”

Section: Turbulence Generationmentioning

confidence: 99%

“…Depending on the application, TSTs can be placed either as individual deployments for niche markets [4] or in large arrays (farm configurations) to maximize the electricity produced at a given site [3,5]. There have been several advanced deployments towards installing full-scale arrays or farms of TSTs in the European Union, a review of these arrays can be found elsewhere [6,7]. In the United States, Verdant Power Inc. is installing an array of tidal turbines as a part of the Roosevelt Island Tidal Energy (RITE) project; a total of ten tri-frames with a three-bladed turbine positioned in a triangular arrangement [8] will be deployed in the East River in New York City in 2020 as a part of a Phase 3 U.S. Department of Energy demonstration project [9].…”

Section: Introductionmentioning

confidence: 99%

Performance and near-wake characterization of a tidal current turbine in elevated levels of free stream turbulence

Vinod

Banerjee

2019

Applied Energy

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Tidal turbines are deployed in sites which have elevated levels of free stream turbulence (FST).Accounting for elevated FST on their operation become vital from a design standpoint. Detailed experimental measurements of the dynamic near-wake of a tidal turbine model in elevated FST environments is presented; an active grid turbulence generator developed by our group was used to seed in the elevated FST and evaluate the influence of turbulence intensity (Ti) and inflow integral length scale (L) on the near-wake of the turbine. Three inflow conditions are tested: a quasi-laminar flow with Ti ~ 2.2% and two elevated Ti (~12-14%) cases, one with L ~ 0.4D (D is the turbine diameter) and the other where L~ D. Elevated Ti cases was found to increase the standard deviation of rotor torque by 4.5 times the value in quasi-laminar flow. Energy recovery was also found to be accelerated; at X/D=4, the percentage of inflow energy recovered was 37% and was twice the corresponding value in quasi-laminar flow. Elevated FST was observed to disrupt the rotational character of the wake; the drop in swirl number ranged between 12% at X/D=0.5 to 71% at X/D=4. Elevated Ti also resulted in L that were considerably larger (> 2 times) than the quasi-laminar flow case. An increase in inflow integral length scale (from 0.4D to D) was observed to result in enhanced wake Ti, wake structures and anisotropy; however, no noticeable influence was found on the rate of wake recovery.

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“…Clarke et al represented the wake reduction and inter blade-spacing optimization for the contra-rotating turbine using CFD [8]. Morris et al displayed the swirl characteristics for the various number of blades and estimation by swirl number [9]. Jo et al checked the wake characteristics by the influence of the blade tip shape using the experimental and numerical method [10].…”

Section: Introductionmentioning

confidence: 99%

A Numerical Prediction of Tip Vortices from Tandem Propellers in the Counter-Rotating Type Tidal Stream Power Unit

Jung¹,

Kanemoto²,

Pin³

2017

JPEE

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Ocean energy has a potential of providing a large amount of renewable energy around the world. One of the forms of ocean energy, tidal stream power is widely recognized as the continuous, predictable and eco-friendly ocean energy source. Unique tandem propellers that can counter-rotate have been designed to generate electric power effectively from a tidal stream. This type of power unit has several advantages compare to the conventional unit with a single propeller. At the design of the tidal stream power unit, it is important to investigate the structure of the tip vortex tubes shedding to predict the load of the propeller. In this research, we investigated the tip vortex shedding using the CFD method for the conventional single propeller and counter-rotating type tandem propellers and estimated the performance efficiency using RANS (Reynolds Averaged Navier-Stokes) model and we confirmed the limitation of RANS model on the calculation of the tip vortex stretching.

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Evaluation of the swirl characteristics of a tidal stream turbine wake

Cited by 26 publications

References 10 publications

Validation of Tidal Stream Turbine Wake Predictions and Analysis of Wake Recovery Mechanism

Validation of Tidal Stream Turbine Wake Predictions and Analysis of Wake Recovery Mechanism

Performance and near-wake characterization of a tidal current turbine in elevated levels of free stream turbulence

A Numerical Prediction of Tip Vortices from Tandem Propellers in the Counter-Rotating Type Tidal Stream Power Unit

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