Large-eddy simulations of wind-farm wake characteristics associated with a low-level jet

Ji Sung Na, Eunmo Koo, Emilia Kyung Jin, Rodman Linn, Seung Chul Ko, Domingo Muñoz-Esparza, Joon Sang Lee

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

In this study, we performed a suite of flow simulations for a 12-wind-turbine array with varying inflow conditions and lateral spacings, and compared the impacts of the flow on velocity deficit and wake recovery. We imposed both laminar inflow and turbulent inflows, which contain turbulence for the Ekman layer and a low-level jet (LLJ) in the stable boundary layer. To solve the flow through the wind turbines and their wakes, we used a large-eddy simulation technique with an actuator-line method. We compared the time series for the velocity deficit at the first and rear columns to observe the temporal change in velocity deficit for the entire wind farm. The velocity deficit at the first column for LLJ inflow was similar to that for laminar inflow. However, the magnitude of velocity deficit at the rear columns for the case with LLJ inflow was 11.9% greater because of strong wake recovery, which was enhanced by the vertical flux of kinetic energy associated with the LLJ. To observe the spatial transition and characteristics of wake recovery, we performed statistical analyses of the velocity at different locations for both the laminar and LLJ inflows. These studies indicated that strong wake recovery was present, and a kurtosis analysis showed that the probability density function for the streamwise velocity followed a Gaussian distribution. In a quadrant analysis of the Reynolds stress, we found that the ejection and sweep motions for the LLJ inflow case were greater than those for the laminar inflow case.

Original languageEnglish
Pages (from-to)163-173
Number of pages11
JournalWind Energy
Volume21
Issue number3
DOIs
Publication statusPublished - 2018 Mar

Fingerprint

Large eddy simulation
Farms
Recovery
Wind turbines
Flow simulation
Gaussian distribution
Kinetic energy
Probability density function
Time series
Boundary layers
Turbulence
Actuators
Fluxes

All Science Journal Classification (ASJC) codes

  • Renewable Energy, Sustainability and the Environment

Cite this

Na, J. S., Koo, E., Jin, E. K., Linn, R., Ko, S. C., Muñoz-Esparza, D., & Lee, J. S. (2018). Large-eddy simulations of wind-farm wake characteristics associated with a low-level jet. Wind Energy, 21(3), 163-173. https://doi.org/10.1002/we.2152
Na, Ji Sung ; Koo, Eunmo ; Jin, Emilia Kyung ; Linn, Rodman ; Ko, Seung Chul ; Muñoz-Esparza, Domingo ; Lee, Joon Sang. / Large-eddy simulations of wind-farm wake characteristics associated with a low-level jet. In: Wind Energy. 2018 ; Vol. 21, No. 3. pp. 163-173.
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Na, JS, Koo, E, Jin, EK, Linn, R, Ko, SC, Muñoz-Esparza, D & Lee, JS 2018, 'Large-eddy simulations of wind-farm wake characteristics associated with a low-level jet', Wind Energy, vol. 21, no. 3, pp. 163-173. https://doi.org/10.1002/we.2152

Large-eddy simulations of wind-farm wake characteristics associated with a low-level jet. / Na, Ji Sung; Koo, Eunmo; Jin, Emilia Kyung; Linn, Rodman; Ko, Seung Chul; Muñoz-Esparza, Domingo; Lee, Joon Sang.

In: Wind Energy, Vol. 21, No. 3, 03.2018, p. 163-173.

Research output: Contribution to journalArticle

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T1 - Large-eddy simulations of wind-farm wake characteristics associated with a low-level jet

AU - Na, Ji Sung

AU - Koo, Eunmo

AU - Jin, Emilia Kyung

AU - Linn, Rodman

AU - Ko, Seung Chul

AU - Muñoz-Esparza, Domingo

AU - Lee, Joon Sang

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AB - In this study, we performed a suite of flow simulations for a 12-wind-turbine array with varying inflow conditions and lateral spacings, and compared the impacts of the flow on velocity deficit and wake recovery. We imposed both laminar inflow and turbulent inflows, which contain turbulence for the Ekman layer and a low-level jet (LLJ) in the stable boundary layer. To solve the flow through the wind turbines and their wakes, we used a large-eddy simulation technique with an actuator-line method. We compared the time series for the velocity deficit at the first and rear columns to observe the temporal change in velocity deficit for the entire wind farm. The velocity deficit at the first column for LLJ inflow was similar to that for laminar inflow. However, the magnitude of velocity deficit at the rear columns for the case with LLJ inflow was 11.9% greater because of strong wake recovery, which was enhanced by the vertical flux of kinetic energy associated with the LLJ. To observe the spatial transition and characteristics of wake recovery, we performed statistical analyses of the velocity at different locations for both the laminar and LLJ inflows. These studies indicated that strong wake recovery was present, and a kurtosis analysis showed that the probability density function for the streamwise velocity followed a Gaussian distribution. In a quadrant analysis of the Reynolds stress, we found that the ejection and sweep motions for the LLJ inflow case were greater than those for the laminar inflow case.

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Na JS, Koo E, Jin EK, Linn R, Ko SC, Muñoz-Esparza D et al. Large-eddy simulations of wind-farm wake characteristics associated with a low-level jet. Wind Energy. 2018 Mar;21(3):163-173. https://doi.org/10.1002/we.2152