Volume 3, issue 2 | Copyright
Wind Energ. Sci., 3, 589-613, 2018
https://doi.org/10.5194/wes-3-589-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research articles 04 Sep 2018

Research articles | 04 Sep 2018

Large-eddy simulation sensitivities to variations of configuration and forcing parameters in canonical boundary-layer flows for wind energy applications

Jeffrey D. Mirocha1, Matthew J. Churchfield2, Domingo Muñoz-Esparza4,a, Raj K. Rai3, Yan Feng5, Branko Kosović9, Sue Ellen Haupt9, Barbara Brown9, Brandon L. Ennis6, Caroline Draxl2, Javier Sanz Rodrigo7, William J. Shaw3, Larry K. Berg3, Patrick J. Moriarty2, Rodman R. Linn4, Veerabhadra R. Kotamarthi5, Ramesh Balakrishnan5, Joel W. Cline8, Michael C. Robinson2,8, and Shreyas Ananthan8,b Jeffrey D. Mirocha et al.
  • 1Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
  • 2National Renewable Energy Laboratory, Golden, CO 80401, USA
  • 3Pacific Northwest National Laboratory, Richland, WA 99354, USA
  • 4Los Alamos National Laboratory, Los Alamos, NM 87545, USA
  • 5Argonne National Laboratory, Lemont, IL 60439, USA
  • 6Sandia National Laboratories, Albuquerque, NM 87185, USA
  • 7Centro Nacional de Energías Renovables, Sarriguren, Navarra, 31621E, Spain
  • 8US Department of Energy, Wind Energy Technology Office, Washington DC 20585, USA
  • 9National Center for Atmospheric Research, Boulder, CO 80305, USA
  • acurrent address: National Center for Atmospheric Research, Boulder, CO 80305, USA
  • bcurrent address: National Renewable Energy Laboratory, Golden, CO 80401, USA

Abstract. The sensitivities of idealized large-eddy simulations (LESs) to variations of model configuration and forcing parameters on quantities of interest to wind power applications are examined. Simulated wind speed, turbulent fluxes, spectra and cospectra are assessed in relation to variations in two physical factors, geostrophic wind speed and surface roughness length, and several model configuration choices, including mesh size and grid aspect ratio, turbulence model, and numerical discretization schemes, in three different code bases. Two case studies representing nearly steady neutral and convective atmospheric boundary layer (ABL) flow conditions over nearly flat and homogeneous terrain were used to force and assess idealized LESs, using periodic lateral boundary conditions. Comparison with fast-response velocity measurements at 10 heights within the lowest 100m indicates that most model configurations performed similarly overall, with differences between observed and predicted wind speed generally smaller than measurement variability. Simulations of convective conditions produced turbulence quantities and spectra that matched the observations well, while those of neutral simulations produced good predictions of stress, but smaller than observed magnitudes of turbulence kinetic energy, likely due to tower wakes influencing the measurements. While sensitivities to model configuration choices and variability in forcing can be considerable, idealized LESs are shown to reliably reproduce quantities of interest to wind energy applications within the lower ABL during quasi-ideal, nearly steady neutral and convective conditions over nearly flat and homogeneous terrain.

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This paper validates the use of idealized large-eddy simulations with periodic lateral boundary conditions to provide boundary-layer flow quantities of interest for wind energy applications. Sensitivities to model formulation, forcing parameter values, and grid configurations were also examined, both to ascertain the robustness of the technique and to characterize inherent uncertainties, as required for the evaluation of more general wind plant flow simulation approaches under development.
This paper validates the use of idealized large-eddy simulations with periodic lateral boundary...
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