Wall modeled immersed boundary method for high Reynolds number flow over complex terrain

Liu, Luoqin; Stevens, Richard J. A. M.

doi:10.1016/j.compfluid.2020.104604

Cited by 15 publications

(6 citation statements)

References 43 publications

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“…We note that the AMD model has been extensively validated and has been shown to give similar predictions to the well‐known Lagrangian‐averaged scale‐dependent SGS model (Bou‐Zeid et al ., 2005; Gadde et al ., 2020). To confirm that the main findings do not depend on the employed SGS model, we compared the results for the lowest and highest

μ_{N}

with results obtained using the standard Smagorinsky model (Smagorinsky, 1963; Mason and Thomson, 1992; Liu and Stevens, 2020).…”

Section: Large‐eddy Simulation Frameworkmentioning

confidence: 86%

Geostrophic drag law for conventionally neutral atmospheric boundary layers revisited

Liu

Gadde

Stevens

2020

Quart J Royal Meteoro Soc

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The geostrophic drag law (GDL), which predicts the geostrophic drag coefficient and the cross‐isobaric angle, is relevant for meteorological applications such as wind energy. For conventionally neutral atmospheric boundary layers (CNBLs) capped by an inversion, the GDL coefficients A and B are affected by the inversion strength and latitude, expressible via the ratio of the Brunt–Väisälä frequency (N) to the Coriolis parameter (f). We present large‐eddy simulations (LES) covering a wider range of N/|f| than considered previously, and show that A and B obtained from carefully performed LES collapse to a single curve when plotted against N/|f|. This verifies the GDL for CNBLs over an extended range of N/|f| within LES. Additionally, in agreement with atmospheric observations, we show that using A = 1.9 and B = 4.4 accurately predicts the geostrophic drag coefficient in the limit of weak inversion strength or high latitude (N/|f|≲300). However, due to the strong dependence of B on N/|f|, corresponding predictions for the cross‐isobaric angle are less accurate. As we find significant deviations between the LES results and the original parameterization of the GDL for CNBLs, we update the corresponding model coefficients.

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μ_{N}

with results obtained using the standard Smagorinsky model (Smagorinsky, 1963; Mason and Thomson, 1992; Liu and Stevens, 2020).…”

Section: Large‐eddy Simulation Frameworkmentioning

confidence: 86%

Geostrophic drag law for conventionally neutral atmospheric boundary layers revisited

Liu

Gadde

Stevens

2020

Quart J Royal Meteoro Soc

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“…For a detailed description and validation of our code we refer the reader to Refs. [31][32][33] The wind turbines are modeled using an actuator disk approach in which the free-stream velocity U ∞ is used to calculate the turbine force F wt…”

Section: A Numerical Methodsmentioning

confidence: 99%

“…Following Abkar and Porté-Agel [41], we first perform time-averaging of the filtered momentum equation [31][32][33],…”

Section: Kinetic Energy Budget Analysismentioning

confidence: 99%

Enhanced wind-farm performance using windbreaks

Liu,

Stevens

2021

Preprint

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The flow speed-up generated by windbreaks can be used to increase the power production of wind turbines. However, due to the increased drag imposed by the windbreaks, their use in large wind turbine arrays has been questioned. We use large eddy simulations to show that windbreaks can increase the power production of large wind farms. A crucial finding is that windbreaks in a wind farm should be much lower than for a single turbine case. In fact, the optimal windbreak for an isolated turbine can reduce wind farm performance. The optimal windbreak height in a wind farm namely depends on the right balance between flow speed-up over the windbreak and the drag imposed by all windbreaks in the farm. The increased performance is a result of the favorable total pressure flux created by the windbreaks.

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“…At the University of Twente, we develop a pseudo-spectral LES code 36,37 that is related to the LESGO code, which originates from the work by Albertson, 38 and later contributions by Bou-Zeid et al, 39 Meyers and Meneveau, 40 Calaf et al, 41 Stevens et al, 42 and Martínez-Tossas et al 9,33 The computational grids are uniformly distributed in the horizontal directions and are staggered in the vertical direction. The first vertical velocity grid plane is located at the ground, while the first horizontal velocity grid planes are located at half grid distance above the ground.…”

Section: Pseudo-spectral Les Solvermentioning

confidence: 99%

Evaluating the accuracy of the actuator line model against blade element momentum theory in uniform inflow

et al. 2022

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We evaluate the accuracy of the actuator line model (ALM) approach by performing simulations for the NREL 5‐MW wind turbine in uniform inflow using three large eddy simulation codes. The power and thrust coefficients obtained using the three codes agree within 1% when the grid spacing normalΔgrid≤5.25 m and are cross‐validated against blade element momentum (BEM) theory. We find that the results of ALM converge towards BEM theory without the need for tip correction when the numerical resolution is increased. For normalΔgrid=0.98 m, the difference between the power and thrust coefficient obtained using ALM and BEM is 4.5% and 2.1%, respectively, although we note that no absolute convergence between ALM and BEM can be obtained as both models use different assumptions, such as the use of a force projection method in the ALM. The difference in the local axial and tangential forces along the blades obtained from ALM simulations using normalΔgrid=1.97 m and normalΔgrid=0.98 m can be as large as 10%. The effect of the number of actuator points on the obtained turbine power and thrust coefficients is limited as the results converge when the spacing between the actuator points is about three times the grid spacing. This insight on the required number of blade points can be used to improve the efficiency of actuator line simulations.

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Wall modeled immersed boundary method for high Reynolds number flow over complex terrain

Cited by 15 publications

References 43 publications

Geostrophic drag law for conventionally neutral atmospheric boundary layers revisited

Geostrophic drag law for conventionally neutral atmospheric boundary layers revisited

Enhanced wind-farm performance using windbreaks

Evaluating the accuracy of the actuator line model against blade element momentum theory in uniform inflow

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