Simulating Urban Effects within a Diagnostic Wind Field Model
The atmospheric dispersion of hazardous materials within the urban environment is a topic of great current interest. Urban structures have been shown/are known to cause overall slowing of the winds, channeling through street canyons, heat island phenomena, wake vortices and enhanced turbulence. Simulations that explicitly resolve individual buildings are limited by computational requirements to domains of a few kilometers. For models that simulate regions covering tens of kilometers with resolutions on the order of a kilometer, the effects of individual buildings must be parameterized by incorporating area-averaged canopy effects. For emergency response applications, results must be provided significantly faster than real time. ADAPT (Sugiyama and Chin, 1998) is a diagnostic model used by the Department of Energy's National Atmospheric Release Advisory Capability (NARAC) at Lawrence Livermore National Laboratory. It produces non-divergent wind, turbulence, and other meteorological fields required by the NARAC dispersion model LODI (Nasstrom et al., 2000). We have incorporated an urban parameterization into ADAPT for simulations with resolutions on the order of a kilometer. We have concentrated upon parameterizing what we believe are the most significant impacts of the urban canopy--the reduction of the mean velocity and the increased turbulence. The parameterization we have implemented is a modification of standard similarity theory based on the definition of an urban roughness layer, which is completely contained in the surface layer. Within this layer, the similarity parameters such as friction velocity and Monin-Obukhov length are taken to be functions of height rather than constant. The resultant vertical profiles evidence a slowing of the wind and an increase in turbulence compared with the standard similarity profile.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 15005949
- Report Number(s):
- UCRL-JC-142621; TRN: US200402%%236
- Resource Relation:
- Conference: 3rd International Symposium on Environmental Hydraulics with a Special Theme in Urban Fluid Dynamics, Tempe, AZ (US), 12/05/2001--12/08/2001; Other Information: PBD: 19 Jul 2001
- Country of Publication:
- United States
- Language:
- English
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