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Modeling flow around bluff bodies and predicting urban dispersion using large eddy simulation.
Yu-Heng Tseng1, Charles Meneveau, Marc B Parlange
1Department of Mechanical Engineering, Center for Environmental and Applied Fluid Mechanics, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA.
Environmental Science & Technology
|May 11, 2006
Summary
This study introduces a large eddy simulation (LES) tool for urban air pollution modeling. It establishes minimum grid resolutions and subgrid model requirements for accurate dispersion simulations in complex urban environments.
Area of Science:
- Environmental fluid dynamics
- Computational atmospheric science
- Urban meteorology
Background:
- Urban air pollutant transport is complex due to topography.
- Traditional models struggle with detailed urban geometry and flow unsteadiness.
Purpose of the Study:
- To develop and validate a large eddy simulation (LES) tool for urban dispersion.
- To determine minimum grid resolution and subgrid model requirements for urban LES.
Main Methods:
- Developed a new dynamic subgrid closure and boundary treatment for LES.
- Validated the model on realistic urban layouts and conducted grid refinement studies.
- Compared performance of various subgrid models for urban flow simulations.
Main Results:
- Established that 6-8 grid points across bluff bodies are needed for meaningful results.
- Dynamic Lagrangian subgrid models provide more realistic subgrid-scale viscosity and velocity spectra.
- LES offers advantages over traditional methods for complex urban boundary details and flow unsteadiness.
Conclusions:
- Defined essential requirements for applying LES to urban atmospheric boundary layer flow and scalar transport.
- LES can accurately simulate pollutant dispersion and evaluate extreme event probabilities in cities.
- The developed LES tool is suitable for realistic urban geometry simulations.