Large-Eddy Simulations of Atmospheric Flows Over Complex Terrain Using the Immersed-Boundary Method in the Weather Research and Forecasting Model
Atmospheric flow over complex terrain, particularly recirculation flows, greatly influences wind-turbine siting, forest-fire behaviour, and trace-gas and pollutant dispersion. However, there is a large uncertainty in the simulation of flow over complex topography, which is attributable to the type of turbulence model, the subgrid-scale (SGS) turbulence parametrization, terrain-following coordinates, and numerical errors in finite-difference methods. Here, we upgrade the large-eddy simulation module within the Weather Research and Forecasting model by incorporating the immersed-boundary method into the module to improve simulations of the flow and recirculation over complex terrain. Simulations over the Bolund Hill indicate improved mean absolute speed-up errors with respect to previous studies, as well an improved simulation of the recirculation zone behind the escarpment of the hill. With regard to the SGS parametrization, the Lagrangian-averaged scale-dependent Smagorinsky model performs better than the classic Smagorinsky model in reproducing both velocity and turbulent kinetic energy. A finer grid resolution also improves the strength of the recirculation in flow simulations, with a higher horizontal grid resolution improving simulations just behind the escarpment, and a higher vertical grid resolution improving results on the lee side of the hill. Our modelling approach has broad applications for the simulation of atmospheric flows over complex topography.
KeywordsBolund Hill experiment Complex terrain Immersed-boundary method Large-eddy simulation Weather Research and Forecasting model
We thank Brian Lamb, Eric Russell, Justine Missik, Zhongming Gao, and Raleigh Grysko for their comments, which greatly improved this work. We are grateful to three anonymous reviewers for their constructive suggestions, which also greatly improved the manuscript. We acknowledge support by National Science Foundation AGS under Grants #1419614. We acknowledge high-performance computing support from Yellowstone (ark:/85065/d7wd3xhc) provided by NCAR’s Computational and Information Systems Laboratory, sponsored by the National Science Foundation.
- Grinstein FF, Margolin LG, Rider WJ (eds) (2007) Implicit large eddy simulation: computing turbulent fluid dynamics. Cambridge University Press, CambridgeGoogle Scholar
- Mohd-Yusof J (1997) Combined immersed-boundary/B-spline methods for simulations of flow in complex geometries. Annual Research Briefs, Center for Turbulence Research, NASA Ames/Stanford Univ 317–327Google Scholar
- Sadique J, Yang XIA, Meneveau C, Mittal R (2017) Aerodynamic properties of rough surfaces with high aspect-ratio roughness elements: effect of aspect ratio and arrangements. Boundary-Layer Meteorol 163:203–224Google Scholar
- Senocak I, Ackerman AS, Stevens DE, Mansour NN (2004) Topography modeling in atmospheric flows using the immersed boundary method. Annual Research Briefs, Center for Turbulence Research, NASA Ames/Stanford Univ 331–341Google Scholar
- Skamarock W, Klemp J, Dudhia J, Gill D, Barker D, Duda M, Huang X, Wang W, Powers J (2008) A description of the advanced research WRF version 3. NCAR, BoulderGoogle Scholar
- Yang XIA, Sadique J, Mittal R, Meneveau C (2015b) Integral wall model for large eddy simulations of wall-bounded turbulent flows. Phys Fluids 27:025112–33Google Scholar
- Yeow TS, Cuerva-Tejero A, Perez-Alvarez J (2015) Reproducing the Bolund experiment in wind tunnel. Wind Energy 18:153–169Google Scholar