For predictions of flow in urban or complex terrain, large-eddy simulations (LES) which explicitly resolve buildings or terrain features are required for capturing the complexities of turbulence. However, changing weather conditions can also affect flow, which requires that a mesoscale model provide boundary conditions to the large-eddy simulations. Nesting a large-eddy simulation within a mesoscale model requires nuanced representations of turbulence.

Our group has improved the Weather and Research Forecating model's (WRF) large-eddy simulation capability by implementing the Nonlinear Backscatter model with Anisotropy (NBA) SFS model following Kosoviæ (1997) and an explicit filtering and reconstruction technique to compute the Resolvable Subfilter-Scale (RSFS) stresses (following Chow et al, 2005). We demonstrate approaches to nesting LES within a mesoscale simulation for urban (based on the Joint URBAN 2003 dataset) and complex terrain (farms of wind turbines in hilly regions) applications.

This work is performed under the auspices of the U.S. Department of Energy by

Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.