Hairpin Structures in a Turbulent Boundary Layer under Stalled-Airfoil-Type Flow Conditions

Maciel, Yvan; Mayam, Mohammad Hossein Shafiei

doi:10.1007/978-3-642-02225-8_48

Cited by 4 publications

(3 citation statements)

References 3 publications

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“…They also compute the maximum azimuthal velocity given by the Gaussian model by obtaining the circulation from the surface integral of the out-of-plane component of vorticity inside the vortex section. Maciel and Shafiei Mayam (2010) do not rely on any theoretical vortex model to study the properties of spanwise and hairpin-like vortices in spanwise-wall normal planes of an adverse-pressuregradient boundary layer. They use directly the vortex detection function k ci , with thresholds applied, to compute the vortex characteristics.…”

Section: Introductionmentioning

confidence: 99%

A method for characterizing cross-sections of vortices in turbulent flows

Maciel¹,

Robitaille²,

Rahgozar³

2012

International Journal of Heat and Fluid Flow

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Section: Introductionmentioning

confidence: 99%

A method for characterizing cross-sections of vortices in turbulent flows

Maciel¹,

Robitaille²,

Rahgozar³

2012

International Journal of Heat and Fluid Flow

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“…The and proposed by many investigators for the identification of vortices [43][44][45][46][47][48][49][50][51]. In this study, the ci λ method [47] is used to extract the vortices.…”

Section: Turbulence Structuresmentioning

confidence: 99%

Large Eddy Simulation of flow around a single and two in-line horizontal-axis wind turbines

Allah

Mayam²

2017

Energy

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A Large Eddy Simulation (LES) has been employed in order to study the flow field in a single-wind turbine and in two in-line wind turbines. The present study focuses on the flow around a horizontal axis wind turbine in a virtual wind tunnel. The anisotropic residual stress tensor is driven by the Smagorinsky model. The results are consistent with experimental data presented in literature. Streamwise velocity is increased and cross stream velocity is decreased as wake moves in downstream direction. A faster rate of wake recovery is seen for the two in-line setup. The results reveal that turbulence intensity is increased by increasing the downstream distance and two in-line turbines show greater intensity. Wind turbine performance can be affected by the turbulent structures. If this phenomenon occurs, information about turbulent structures would be useful in order to investigate the effect of turbulent structures on wind turbine performance. As a result, we aim to reveal the effect of turbulent structures, by using the ci  technique in this study, and to investigate the performance of wind turbines in different conditions. Furthermore, the effects of blade rotation direction are studied in this paper. It is concluded that wind turbine efficiency is increased by 4%.

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“…Hence, a precise vortex extraction method is required to reveal the vortical structures. Various tools and algorithms have been proposed and used by many investigators to identify vortices[43][44][45][46][47][48][49][50][51]. The ci  method[51] is used to extract vortices in the present study.…”

mentioning

confidence: 99%

Effects of blade rotation direction in the wake region of two in-line turbines using Large Eddy Simulation

Veisi

Mayam²

2017

Applied Energy

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In the present work, flow around a horizontal axis wind turbine is investigated in co-rotating and counter-rotating configurations. Large Eddy Simulation (LES) has been employed in order to study the effect of rotation direction of the downstream turbine in a two in-line setup. The results are in good agreement with presenting experimental data in literatures. The power efficiency of the downstream turbine has increased about 4% in the counterrotating configuration rather than co-rotating configuration with the same separation distance (3D). The power efficiency of the downstream turbine increased about 7% by decreasing the separation distance to 1D. The improved efficiency in the counter-rotating configuration is due to the flow rotation direction of the upstream turbine. The results revealed in both configurations that streamwise velocity is almost identical, while lateral velocities are changed greatly. Lateral velocities are decreased by moving in a downstream direction. Hence, the benefit of this configuration is obtained by lower separation distance. The authors suggested counter-rotating configuration for the terrain with a high density of installed wind turbines and believed that operating the wind turbines in counter-rotating configuration will not only improve the total efficiency of two in-line turbines, but will also considerably reduce the space they require. Since the oscillations of power coefficient are so high, the exact location of encountering the vortices on downstream blades should be determined to improve the power coefficient of two in line turbines. So, further studies are suggested to extract and track the vortices for future work to increase the efficiency of wind farms.

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Hairpin Structures in a Turbulent Boundary Layer under Stalled-Airfoil-Type Flow Conditions

Cited by 4 publications

References 3 publications

A method for characterizing cross-sections of vortices in turbulent flows

A method for characterizing cross-sections of vortices in turbulent flows

Large Eddy Simulation of flow around a single and two in-line horizontal-axis wind turbines

Effects of blade rotation direction in the wake region of two in-line turbines using Large Eddy Simulation

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