Grantee Research Project Results
2004 Progress Report: Large Eddy Simulation of Dispersion in Urban Areas
EPA Grant Number: R828771C004Subproject: this is subproject number 004 , established and managed by the Center Director under grant R828771
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Center for the Study of Childhood Asthma in the Urban Environment
Center Director: Hansel, Nadia
Title: Large Eddy Simulation of Dispersion in Urban Areas
Investigators: Parlange, Marc , Helble, Joseph J. , Ondov, John M. , Meneveau, Charles
Current Investigators: Parlange, Marc , Meneveau, Charles
Institution: University of Connecticut , The Johns Hopkins University , University of Maryland - College Park
Current Institution: The Johns Hopkins University
EPA Project Officer: Aja, Hayley
Project Period: October 1, 2001 through September 30, 2007
Project Period Covered by this Report: October 1, 2003 through September 30, 2004
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (2001) Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management
Objective:
The objectives of this research project are to: (1) implement and verify the John Hopkins University—Large Eddy Simulation (LES) code for simulating pollutant transport in urban environments; and (2) simulate pollutant transport and dispersion in downtown Baltimore, Maryland.
Progress Summary:
The computational simulation tool is developed to address potential exposure pathways in urban environments from airborne particles. Air pollution is affected critically by wind that transports pollutants from the emitter to other locations. Computer simulations of air movement and pollutant transport in the urban environments are especially challenging because of the complex ground topology typically found in cities. A building cluster, consisting of a group of buildings of roughly comparable size, is expected to provide the most complicated flow patterns because the flow interference among buildings needs to be taken into account. In particular, it is impossible to resolve all flow features in the atmospheric flow over an urban canopy. Typically in such applications, fairly coarse grids must be used where the subgrid-scale (SGS) model is expected to play a crucial role. The previous progress described the use and tests of immersed boundary method (IBM) for complex geometry with realistic logarithmic boundary condition and showed that the minimum requirement for reasonably resolving the flow around a bluff body is roughly 6 to 8 grid points across the body. This gives us clear guidance that, using the present simulation tool and SGS models, we will have to resolve individual buildings with at least 6 points across each building. The goal of this year’s research has been to extend the LES code to a cluster of buildings and an urban area and improve simulations of flow and pollutant transport within urban environments. Applying the IBM in atmospheric boundary layer flows allows more efficient computations.
Our modeling progress to date has been to: (1) perform several validation tests for turbulent flow over a cluster of buildings with logarithmic type boundary condition; (2) simulate turbulent flow in an urban area (Baltimore, Maryland); and (3) investigate the pollutant transport and dispersion within a city. To simulate the flow over a building cluster, we use a computational domain consisting of an array of nine cubes with periodic boundary horizontally. This flow was investigated experimentally by Meinders and Hanjalic (1999) and was an important benchmark test because many complicating factors are involved (e.g., flow separation, streamline curvature, recirculation, and vortex shedding, chaotic three-dimensional wake structure, and the layout of the cubes). Our simulations are carried out at infinite Reynolds number. The streamwise velocity profiles obtained by the LES with three different SGS models are compared to the experiments of Meinders and Hanjalic (1999) at various downstream distances. Figure 1(a) shows the vertical profiles of the mean streamwise velocity in the vertical center plane y/H = 0 for the cube from five selected x-locations. Figure 1(b) shows the horizontal profiles of the mean streamwise velocity at z/H = 0.5 (half cube height) at the same locations. The predicted mean streamwise velocity agrees reasonably well with the experimental results. Small discrepancies occur in the recirculation region behind the cubes. Overall, there is generally good agreement between the LES results and the experimental measurements on such a coarse grid. The difference in the mean streamwise velocity is small among the SGS models. In such a highly turbulent flow, the logarithmic boundary condition seems adequate and matches the experimental data reasonably well (x/H = 0.3).
The chosen coarse grid resolutions are required for simulations of atmospheric boundary layer flow over urban canopies where individual buildings are resolved at least approximately on the grid. In the validation, the effects of different SGS models on the mean flow are found not to be major (Tseng, et al., 2004). The results are in a fair agreement with the experimental data for all versions of the eddy-viscosity models. We observed that the dynamic Lagrangian models give a physically more realistic SGS viscosity field (which vanishes in laminar portions in front of the bluff body when a laminar inflow is present). In general the scale-dependent Lagrangian model produces larger Smagorinsky coefficient than the scale-invariant one, leading to distributions of reduced resolved RMS velocities especially in the boundary layers near the bluff bodies. With these results as guidance, we apply the LES code with the presently developed IBM, and Lagrangian SGS model, to a developing urban canopy flow.
To study the flow and pollutant transport around realistic buildings with available data, we further extend the model to simulate the flow around downtown Baltimore, Maryland. The city consists of several skyscrapers and buildings (see Figure 2(a)). Representative buildings (e.g., Legg Masson building, Bank of America building, Commerce Place, and others) are illustrated in Figure 2(b) and used in our simulation. Because the wind flows eastward frequently from the annual statistics, we force the turbulent inflow from the west. We also parameterized the effects of water in Inner Harbor based on different (lower) roughness (Bou-Zeid, et al., 2004). The computational model provides an efficient and useful tool to investigate the pollutant transport and turbulent mixing within the city. The pollutants are transported downstream and detoured because of the building structures (see Figure 3). Strong turbulent mixing is found and the plume is trapped within the building cluster. The pollutants accumulate locally among the buildings. In addition, the velocity field becomes very chaotic behind the building cluster.
Future Activities:
The present computational model has been tested and validated successfully using several flow configurations with geometries of increasing complexity. The preliminary results in the flow over a realistic urban area (downtown Baltimore, Maryland) are highly promising. As next steps, we will release the possible pollutant sources from different locations and test the predictions of flow within the city. The effects of various weather conditions and variable winds will be investigated.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other subproject views: | All 23 publications | 3 publications in selected types | All 3 journal articles |
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Other center views: | All 108 publications | 22 publications in selected types | All 20 journal articles |
Type | Citation | ||
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Bou-Zeid E, Meneveau C, Parlange MB. Large-eddy simulation of neutral atmospheric boundary layer flow over heterogeneous surfaces: blending height and effective surface roughness. Water Resources Research 2004;40:W02505. |
R828771C004 (2004) R828771C004 (2005) R828771C004 (Final) |
Exit Exit |
Supplemental Keywords:
large eddy simulation, aerosols, lidar, light detection and ranging, toxics, exposure, hazardous substances, assessment, cleanup, risk communication,, RFA, Health, Scientific Discipline, PHYSICAL ASPECTS, Air, particulate matter, Health Risk Assessment, Risk Assessments, Physical Processes, Ecology and Ecosystems, ambient aerosol, ambient air quality, urban air, air toxics, epidemiology, human health effects, contaminant transport, air quality models, airborne particulate matter, contaminant cycling, exposure, air pollution, air sampling, environmental health effects, large eddy simulations, hazardous waste incinerators, human exposure, respiratory impact, airborne aerosols, aerosol composition, ambient particle health effects, PM, urban environment, aersol particles, aerosols, human health risk, hazardous substance contaminationRelevant Websites:
http://pegasus.me.jhu.edu/~meneveau/ Exit
http://www.jhu.edu/~dogee/mbp/ Exit
http://www.jhu.edu/~ceafm/ Exit
Progress and Final Reports:
Original AbstractMain Center Abstract and Reports:
R828771 Center for the Study of Childhood Asthma in the Urban Environment Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R828771C001 Co-Contaminant Effects on Risk Assessment and Remediation Activities Involving Urban Sediments and Soils: Phase II
R828771C002 The Fate and Potential Bioavailability of Airborne Urban
Contaminants
R828771C003 Geochemistry, Biochemistry, and Surface/Groundwater Interactions
for As, Cr, Ni, Zn, and Cd with Applications to Contaminated Waterfronts
R828771C004 Large Eddy Simulation of Dispersion in Urban Areas
R828771C005 Speciation of chromium in environmental media using capillary
electrophoresis with multiple wavlength UV/visible detection
R828771C006 Zero-Valent Metal Treatment of Halogenated Vapor-Phase Contaminants in SVE Offgas
R828771C007 The Center for Hazardous Substances in Urban Environments (CHSUE) Outreach Program
R828771C008 New Jersey Institute of Technology Outreach Program for EPA Region II
R828771C009 Urban Environmental Issues: Hartford Technology Transfer and Outreach
R828771C010 University of Maryland Outreach Component
R828771C011 Environmental Assessment and GIS System Development of Brownfield Sites in Baltimore
R828771C012 Solubilization of Particulate-Bound Ni(II) and Zn(II)
R828771C013 Seasonal Controls of Arsenic Transport Across the Groundwater-Surface Water Interface at a Closed Landfill Site
R828771C014 Research Needs in the EPA Regions Covered by the Center for Hazardous Substances in Urban Environments
R828771C015 Transport of Hazardous Substances Between Brownfields and the Surrounding Urban Atmosphere
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.
Project Research Results
3 journal articles for this subproject
Main Center: R828771
108 publications for this center
20 journal articles for this center