Effects of energetic coherent motions on the power and wake of an axial-flow turbine

Chamorro, Leonardo P.; Hill, Craig; Neary, Vincent S.; Gunawan, Budi; Arndt, Roger E. A.; Sotiropoulos, Fotis

doi:10.1063/1.4921264

Cited by 40 publications

(29 citation statements)

References 23 publications

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“…Many published works studied the nature of the turbulent wake downstream of a hydrokinetic turbine [1,2,3,4,5,6,7,8,9,10], as well as arrays of wind turbines and effects of intra-turbine spacing within arrays [11,12,13,14, 15] using theoretical, experimental and/or computational tools. However, there have been relatively fewer studies on arrays of hydrokinetic turbines.…”

Section: Introductionmentioning

confidence: 99%

Wake characteristics of a TriFrame of axial-flow hydrokinetic turbines

et al. 2017

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An effective way to develop arrays of hydrokinetic turbines in river and tidal channels is to arrange them in TriFrame T M 1 configurations where three turbines are mounted together at the apexes of a triangular frame. This TriFrame can serve as the building block for rapidly deploying multi-turbine arrays. The wake structure of a TriFrame of three model turbines is investigated using both numerical simulations and experiments. In the numerical part, we employ large-eddy simulation (LES) with the curvilinear immersed boundary method (CURVIB) for fully resolving the turbine geometry details to simulate intra-turbine wake interactions in the TriFrame configuration. First, the computed results are compared with experiments in terms of mean flow and turbulence characteristics with overall good agreement. The flow-fields are then analyzed to elucidate the mechanisms of turbine interactions and wake evolution in the TriFrame configuration. We found that the wake of the upstream TriFrame turbine exhibits unique characteristics indicating presence of the Venturi effect as the wake encounters the two downstream turbines. We finally compare the wakes of the TriFrame turbines with that of an isolated single turbine wake to further illustrate how the TriFrame configuration affects the wake characteristics and power production in an array of TriFrames.

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Section: Introductionmentioning

confidence: 99%

Wake characteristics of a TriFrame of axial-flow hydrokinetic turbines

et al. 2017

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“…Furthermore, Singh et al [16] argued that the wind turbines reduce the asymmetry and intermittency in the wake flow, resulting in more homogenized velocity fluctuations as compared to the base flow. From a series of recently conducted experiments, Chamorro et al [17] analyzed the evolution of the large-scale turbulence in the wake of a hydrokinetic turbine, and proposed a new approach to quantifying the wake recovery based on the development of the integral scales, showing that strong coherent motions are more effective than turbulence levels for triggering the break-up of the spiral structure of the tip-vortices [18]. This reveals the influence of energetic motions in the wake characteristics and the power output, which are essential to better assess environmental aspects and establish robust engineering models.…”

Section: Introductionmentioning

confidence: 99%

Effects of Freestream Turbulence in a Model Wind Turbine Wake

et al. 2016

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Abstract:The flow structure in the wake of a model wind turbine is explored under negligible and high turbulence in the freestream region of a wind tunnel at Re ∼ 7 × 10 4 . Attention is placed on the evolution of the integral scale and the contribution of the large-scale motions from the background flow. Hotwire anemometry was used to obtain the streamwise velocity at various streamwise and spanwise locations. The pre-multiplied spectral difference of the velocity fluctuations between the two cases shows a significant energy contribution from the background turbulence on scales larger than the rotor diameter. The integral scale along the rotor axis is found to grow linearly with distance, independent of the incoming turbulence levels. This scale appears to reach that of the incoming flow in the high turbulence case at x/d ∼ 35-40. The energy contribution from the turbine to the large-scale flow structures in the low turbulence case increases monotonically with distance. Its growth rate is reduced past x/d ∼ 6-7. There, motions larger than the rotor contribute ∼50% of the total energy, suggesting that the population of large-scale motions is more intense in the intermediate field. In contrast, the wake in the high incoming turbulence is quickly populated with large-scale motions and plateau at x/d ∼ 3.

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“…However, the similarity in upstream and downstream reduction in bed form

σ_{z_{b}}

values is strikingly similar between the straight and meandering channel experiments. Note that an extended region of reduced bed form variability in height and wavelength is potentially a favorable feature within larger multiturbine deployments because bed form induced turbulence is known to have a strong effect on turbine performance, especially in terms of fluctuating power production and enhanced loads [ Hill et al ., ; Chamorro et al ., ].…”

Section: Discussionmentioning

confidence: 99%

“…Recent work by Chamorro et al . [] examined the effects such coherent eddies have on turbine performance and wake characteristics using vertically oriented cylinders to introduce eddies of various sizes.…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamics and sediment transport in a meandering channel with a model axial‐flow hydrokinetic turbine

Hill

Kozarek

Sotiropoulos

et al. 2016

Water Resources Research

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An investigation into the interactions between a model axial-flow hydrokinetic turbine (rotor diameter, d T 5 0.15 m) and the complex hydrodynamics and sediment transport processes within a meandering channel was carried out in the Outdoor StreamLab research facility at the University of Minnesota St. Anthony Falls Laboratory. This field-scale meandering stream with bulk flow and sediment discharge control provided a location for high spatiotemporally resolved measurements of bed and water surface elevations around the model turbine. The device was installed within an asymmetric, erodible channel cross section under migrating bed form and fixed outer bank conditions. A comparative analysis between velocity and topographic measurements, with and without the turbine installed, highlights the local and nonlocal features of the turbine-induced scour and deposition patterns. In particular, it shows how the cross-section geometry changes, how the bed form characteristics are altered, and how the mean flow field is distorted both upstream and downstream of the turbine. We further compare and discuss how current energy conversion deployments in meander regions would result in different interactions between the turbine operation and the local and nonlocal bathymetry compared to straight channels.

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Effects of energetic coherent motions on the power and wake of an axial-flow turbine

Cited by 40 publications

References 23 publications

Wake characteristics of a TriFrame of axial-flow hydrokinetic turbines

Wake characteristics of a TriFrame of axial-flow hydrokinetic turbines

Effects of Freestream Turbulence in a Model Wind Turbine Wake

Hydrodynamics and sediment transport in a meandering channel with a model axial‐flow hydrokinetic turbine

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