Building resolving large-eddy simulations and comparison with wind tunnel experiments

  • Authors:

  • Piotr K. Smolarkiewicz;Robert Sharman;Jeffrey Weil;Steven G. Perry;David Heist;George Bowker

  • Affiliations:

  • National Center for Atmospheric Research, Boulder, CO 80307, USA;National Center for Atmospheric Research, Boulder, CO 80307, USA;University of Colorado, Cooperative Institute for Research in Environmental Science, Boulder, CO 80309, USA;Atmospheric Sciences Modeling Division, National Oceanic and Atmospheric Administration, Research Triangle Park, NC 27711, USA;Atmospheric Sciences Modeling Division, National Oceanic and Atmospheric Administration, Research Triangle Park, NC 27711, USA;Atmospheric Modeling Division, US Environmental Protection Agency, Research Triangle Park, NC 27711, USA

  • Venue:
  • Journal of Computational Physics
  • Year:
  • 2007

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Abstract

We perform large-eddy simulations (LES) of the flow past a scale model of a complex building. Calculations are accomplished using two different methods to represent the edifice. The first method employs the standard Gal-Chen and Somerville terrain-following coordinate transformation, common in mesoscale atmospheric simulations. The second method uses an immersed boundary approach, in which fictitious body forces in the equations of motion are used to represent the building by attenuating the flow to stagnation within a time comparable to the time step of the model. Both methods are implemented in the same hydrodynamical code (EULAG) using the same nonoscillatory forward-in-time (NFT) incompressible flow solver based on the multidimensional positive definite advection transport algorithms (MPDATA). The two solution methods are compared to wind tunnel data collected for neutral stratification. Profiles of the first- and second-order moments at various locations around the model building show good agreement with the wind tunnel data. Although both methods appear to be viable tools for LES of urban flows, the immersed boundary approach is computationally more efficient. The results of these simulations demonstrate that, contrary to popular opinion, continuous mappings such as the Gal-Chen and Somerville transformation are not inherently limited to gentle slopes. Calculations for a strongly stratified case are also presented to point out the substantial differences from the neutral boundary layer flows.