skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Adaptive Urban Dispersion Integrated Model

Abstract

Numerical simulations represent a unique predictive tool for understanding the three-dimensional flow fields and associated concentration distributions from contaminant releases in complex urban settings (Britter and Hanna 2003). Utilization of the most accurate urban models, based on fully three-dimensional computational fluid dynamics (CFD) that solve the Navier-Stokes equations with incorporated turbulence models, presents many challenges. We address two in this work; first, a fast but accurate way to incorporate the complex urban terrain, buildings, and other structures to enforce proper boundary conditions in the flow solution; second, ways to achieve a level of computational efficiency that allows the models to be run in an automated fashion such that they may be used for emergency response and event reconstruction applications. We have developed a new integrated urban dispersion modeling capability based on FEM3MP (Gresho and Chan 1998, Chan and Stevens 2000), a CFD model from Lawrence Livermore National Lab. The integrated capability incorporates fast embedded boundary mesh generation for geometrically complex problems and full three-dimensional Cartesian adaptive mesh refinement (AMR). Parallel AMR and embedded boundary gridding support are provided through the SAMRAI library (Wissink et al. 2001, Hornung and Kohn 2002). Embedded boundary mesh generation has been demonstrated to be anmore » automatic, fast, and efficient approach for problem setup. It has been used for a variety of geometrically complex applications, including urban applications (Pullen et al. 2005). The key technology we introduce in this work is the application of AMR, which allows the application of high-resolution modeling to certain important features, such as individual buildings and high-resolution terrain (including important vegetative and land-use features). It also allows the urban scale model to be readily interfaced with coarser resolution meso or regional scale models. This talk will discuss details of the approach and present results for some example calculations performed in Manhattan in support of the DHS Urban Dispersion Program (UDP) using some of the tools developed as part of this new capability.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
886682
Report Number(s):
UCRL-PROC-216813
TRN: US200616%%1107
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: Presented at: 86th American Meteorological Society Annual Meeting, Atlanta, GA, United States, Jan 29 - Feb 02, 2005
Country of Publication:
United States
Language:
English
Subject:
17 WIND ENERGY; 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; 54 ENVIRONMENTAL SCIENCES; BOUNDARY CONDITIONS; EFFICIENCY; LAND USE; MESH GENERATION; NAVIER-STOKES EQUATIONS; RESOLUTION; SCALE MODELS; SIMULATION; TURBULENCE

Citation Formats

Wissink, A, Chand, K, Kosovic, B, Chan, S, Berger, M, and Chow, F K. Adaptive Urban Dispersion Integrated Model. United States: N. p., 2005. Web.
Wissink, A, Chand, K, Kosovic, B, Chan, S, Berger, M, & Chow, F K. Adaptive Urban Dispersion Integrated Model. United States.
Wissink, A, Chand, K, Kosovic, B, Chan, S, Berger, M, and Chow, F K. Thu . "Adaptive Urban Dispersion Integrated Model". United States. doi:. https://www.osti.gov/servlets/purl/886682.
@article{osti_886682,
title = {Adaptive Urban Dispersion Integrated Model},
author = {Wissink, A and Chand, K and Kosovic, B and Chan, S and Berger, M and Chow, F K},
abstractNote = {Numerical simulations represent a unique predictive tool for understanding the three-dimensional flow fields and associated concentration distributions from contaminant releases in complex urban settings (Britter and Hanna 2003). Utilization of the most accurate urban models, based on fully three-dimensional computational fluid dynamics (CFD) that solve the Navier-Stokes equations with incorporated turbulence models, presents many challenges. We address two in this work; first, a fast but accurate way to incorporate the complex urban terrain, buildings, and other structures to enforce proper boundary conditions in the flow solution; second, ways to achieve a level of computational efficiency that allows the models to be run in an automated fashion such that they may be used for emergency response and event reconstruction applications. We have developed a new integrated urban dispersion modeling capability based on FEM3MP (Gresho and Chan 1998, Chan and Stevens 2000), a CFD model from Lawrence Livermore National Lab. The integrated capability incorporates fast embedded boundary mesh generation for geometrically complex problems and full three-dimensional Cartesian adaptive mesh refinement (AMR). Parallel AMR and embedded boundary gridding support are provided through the SAMRAI library (Wissink et al. 2001, Hornung and Kohn 2002). Embedded boundary mesh generation has been demonstrated to be an automatic, fast, and efficient approach for problem setup. It has been used for a variety of geometrically complex applications, including urban applications (Pullen et al. 2005). The key technology we introduce in this work is the application of AMR, which allows the application of high-resolution modeling to certain important features, such as individual buildings and high-resolution terrain (including important vegetative and land-use features). It also allows the urban scale model to be readily interfaced with coarser resolution meso or regional scale models. This talk will discuss details of the approach and present results for some example calculations performed in Manhattan in support of the DHS Urban Dispersion Program (UDP) using some of the tools developed as part of this new capability.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Nov 03 00:00:00 EST 2005},
month = {Thu Nov 03 00:00:00 EST 2005}
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share:
  • Numerical simulations represent a unique predictive tool for developing a detailed understanding of three-dimensional flow fields and associated concentration distributions from releases in complex urban settings (Britter and Hanna 2003). The accurate and timely prediction of the atmospheric dispersion of hazardous materials in densely populated urban areas is a critical homeland and national security need for emergency preparedness, risk assessment, and vulnerability studies. The main challenges in high-fidelity numerical modeling of urban dispersion are the accurate prediction of peak concentrations, spatial extent and temporal evolution of harmful levels of hazardous materials, and the incorporation of detailed structural geometries. Current computationalmore » tools do not include all the necessary elements to accurately represent hazardous release events in complex urban settings embedded in high-resolution terrain. Nor do they possess the computational efficiency required for many emergency response and event reconstruction applications. We are developing a new integrated urban dispersion modeling capability, able to efficiently predict dispersion in diverse urban environments for a wide range of atmospheric conditions, temporal and spatial scales, and release event scenarios. This new computational fluid dynamics capability includes adaptive mesh refinement and it can simultaneously resolve individual buildings and high-resolution terrain (including important vegetative and land-use features), treat complex building and structural geometries (e.g., stadiums, arenas, subways, airplane interiors), and cope with the full range of atmospheric conditions (e.g. stability). We are developing approaches for seamless coupling with mesoscale numerical weather prediction models to provide realistic forcing of the urban-scale model, which is critical to its performance in real-world conditions.« less
  • As part of the Clean Air Act Amendments of 1990 (CAAA 1990), legislation was enacted requiring the performance of Risk Management Programs (RMPs) for facilities handling toxic substances and flammable materials. One of the three main components of the RMP is the hazard assessment, which requires the performance of air dispersion modeling and consequence analysis of identified accidental release scenarios for toxic substances and flammable materials. The emissions of toxic materials during accidental releases are typically of short duration, may be released as a vertical jet, and may also exhibit neutrally buoyant or dense gas behavior. The INPUFF model, amore » Gaussian integrated puff model is routinely used to study the dispersion of neutrally buoyant jet releases. Three dispersion algorithms are provided within the INPUFF model for studying the dispersion downwind of a source. The first option allows the use of classical Pasquill-Gifford scheme which is appropriate for rural locations. The second option allows the use of Irwin`s on-site scheme, and the third option allows the incorporation of user defined dispersion characteristics. However, most of the times, Option one is used for performing the dispersion analysis, even for accidental releases in urban areas. The use of INPUFF model with rural dispersion coefficients (Option 1) would result in improper estimates of hazard distances. The EPA has also developed the Industrial Source Complex Short Term (ISCST) Model for studying the atmospheric dispersion of steady state neutrally buoyant releases. A comparison of the rural dispersion coefficients in INPUFF and ISCST models indicated that both models use the same rural dispersion coefficients.« less
  • A simple urban dispersion model is tested that is based on the Gaussian plume model and the Briggs’ urban dispersion curves. A key aspect of the model is that an initial dispersion coefficient (sigma) of 40 m is assumed to apply in the x, y, and z directions in built-up downtown areas. This initial sigma accounts for mixing in the local street canyon and/or building wakes. At short distances (i.e., when the release is in the same street canyon as the receptor and there are no obstructions in between), the initial lateral sigma is assumed to be less, 10 m.more » Observations from tracer experiments during the Madison Square Garden 2005 (MSG05) field study are used for model testing. MSG05 took place in a 1 km by 1 km area in Manhattan surrounding Madison Square Garden. Six different perfluorocarbon tracer (PFT) gases were released concurrently from five different locations around MSG, and concentrations in the air were observed by 20 samplers near the surface and seven samplers on building tops. There were two separate continuous 60 minute tracer release periods on each day, beginning at 9 am and at 11:30 am. Releases took place on two separate days (March 10 and 14). The samplers provided 30 minute averaged PFT concentrations from 9 am through 2 pm. This analysis focuses on the maximum 60-minute averaged PFT gas concentration at each sampler location for each PFT for each release period. Stability was assumed to be nearly neutral, because of the moderate winds and the mechanical mixing generated by the buildings. Input wind direction was the average observed building-top wind direction (285° on March 10 and 315° on March 14). Input wind speed was the average street-level observed wind speed (1.5 m/s for both days). To be considered in the evaluation, both the observed and predicted concentration had to exceed the threshold. Concentrations normalized by source release rate, C/Q, were tested. For all PFTs, samplers, and release times, the median observed and predicted C/Q are within 40% of each other, and 43 % of the time the concentration predictions are within a factor of two of the observations. The scatter plots show that the typical error is about the same magnitude as the mean concentration. When only the surface observations are considered, the performance is better, with the median observed and predicted C/Qs within 10 % of each other. The overall 60 minute-averaged maximum C/Q is underpredicted by about 40 % for the surface samplers and is overpredicted by about 25 % for the building-top samplers.« less
  • Results produced from a 3-D, time-dependent flow model show that dispersion characteristics can be simulated and interpreted in terms of flow conditions and structural configurations. Our previously parameterized 2-D formulations for time constants are modified to include the effect of the orientation of the mean wind relative to the canyon. The parameterizations can be applied to urban air pollution models directly, because the independent parameters are readily available from mesoscale calculations. More numerical studies are planned to characterize turbulent flow in street canyons. The current version of the model will be coupled with an improved module to solve transport equationsmore » for turbulence kinetic energy and turbulence dissipation rate. A three-dimensional, time-dependent flow model has been applied to examine the processes by which pollutants emitted at street level are transported and diffused from street canyons, and to determine the exchange rates of pollutants between street canyons and the air above the canyon.« less
  • The objective of this study is to identify potential long-range sources of mercury within the southeast region of the United States. Preliminary results of a climatological study using the Short-range Layered Atmospheric Model (SLAM) transport model from a select source in the southeast U.S. are presented. The potential for long-range transport from Oak Ridge, Tennessee to Florida is discussed. The transport and transformation of mercury during periods of favorable transport to south Florida is modeled using the Organic Chemistry Integrated Dispersion (ORCHID) model, which contains the transport model used in the climatology study. SLAM/ORCHID results indicate the potential for mercurymore » reaching southeast Florida from the source and the atmospheric oxidation of mercury during transport.« less