Grantee Research Project Results
2005 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: The Johns Hopkins University , University of Connecticut , 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, 2004 through September 30, 2005
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 the project are to: (1) implement and verify the Johns Hopkins University (JHU) – 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:
We have continued to develop and test the computational simulation tool to address potential exposure pathways in urban environments from airborne particles. This past year, we have started to focus on the verification of the LES based upon field measurements. 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 due to 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 6-8 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. In the last report we extended the LES code to a cluster of buildings and an urban area (Baltimore).
This past year we have extended our work to consider the resolution at which building in cities and towns must be resolved to realistically simulate the lower atmosphere. Specifically we have extended this work to the Swiss Federal Institute of Technology (EPFL) campus where an intensive field campaign of the real atmospheric flow in the vicinity of buildings is underway. The EPFL campus (see Figure 1a) is located on the north shore of the Lake of Geneva, a few kilometers west of the center of Lausanne. Situated between the hills of the Jura to the north and the French Alps to the south, the prevailing winds are along the SW to NE axis. The campus is at an altitude of 395 meters above sea level, about 20 meters above the lake, and the surrounding topography has small hills (< 30 m). Experiments underway involve a wide array of instruments to measure the local turbulence and vertical profiles around the buildings. For instance, in Figures 1b,c high resolution wind and temperature profiles are measured with RASS and Sodar systems and heat and momentum fluxes are measured with scintillometers. Other measurement systems include sonic anemometers, radiation, temperature and Raman- lidar profiling of atmospheric water vapor and temperature.
Figure 1. (a) EPFL campus, (b) Sodar and Rass system to measure lower atmospheric temperature and wind profiles respectively, and (c) scintillometer system for heat and momentum flux measurements over buildings.
In the initial testing we restrict ourselves to modeling the flow of a neutral atmospheric boundary layer neglecting considerations regarding atmospheric stability and heating of the building walls due to the diurnal motion of the sun. For example, we have tested three different models of the EPFL buildings as can be seen in Figure 2, with increasing complexity from top to bottom. The y-axis points to the north and the prevailing wind is chosen to be along the x-axis. The different models are chosen to contain various levels of detail with the aim being to understand the required level to best simulate the actual wind fields. The flow field is periodic in the west to east direction and initialized with random perturbations about a log law initial velocity distribution and the simulation is run for sufficient time to establish ten “turnovers” once the kinetic energy of the simulation has stabilized. In Figure 3 the time averaged u component of the velocity field at 10 meters (2 grid points) above the ground for each version of the campus is plotted. It is no surprise that details in the model used strongly influence the smaller structures in the flow. During the final year of the project we will address the role of building resolution, atmospheric stability and the heating of buildings based on comparison with the field experiments. In particular we will address: How much detail in the model of the urban canopy must be taken into account when simulating the flow over an urban area to simulate urban dispersion?
Figure 2. 3D Models of the EPFL Campus in Increasing Detail From Top to Bottom. (a): coarse (b): medium (c): fine.
Figure 3. U Component of the Velocity Field at z = 10 m Averaged Over the Entire Simulation Using the Three Models in Increasing Complexity From Top to Bottom. (colors: blue = 2.6 m/s, red = 5.0 m/s)
Journal Articles on this Report : 2 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 |
|
Bou-Zeid E, Meneveau C, Parlange M. A scale-dependent Lagrangian dynamic model for large eddy simulation of complex turbulent flows. Physics of Fluids 2005;17:025105. |
R828771C004 (2005) R828771C004 (Final) |
Exit Exit |
Supplemental Keywords:
large eddy simulation, aerosols, lidar, light detection and ranging,, 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