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DEVELOPMENT AND APPLICATIONS OF CFD SIMULATIONS SUPPORTING URBAN AIR QUALITY AND HOMELAND SECURITY
Citation:
HUBER, A. H., M. FREEMAN, R. SPENCER, W. SCHWARZ, B. BELL, AND K. KUEHLERT. DEVELOPMENT AND APPLICATIONS OF CFD SIMULATIONS SUPPORTING URBAN AIR QUALITY AND HOMELAND SECURITY. Presented at Symposium on the Urban Environment; AMS Annual Meeting, Atlanta, GA, January 29 - February 02, 2006.
Impact/Purpose:
The objective of this task is to improve EPA's ability to accurately predict the concentrations and deposition of air pollutants in the atmosphere that are known or suspected to cause cancer or other serious health effects to humans, or adverse environmental effects. It is an essential component of EPA's National Air Toxics Assessment (NATA), which seeks to identify and quantify the concentrations and sources of those hazardous air pollutants which are of greatest potential concern, in terms of contribution to population risk. It is a major contributor to NERL's Air Toxics Research Program.
"Air toxics" or "hazardous air pollutants" (HAPs) is a category that covers a large variety of chemicals, which range from relatively non reactive to extremely reactive; can exist in the gas, aqueous, and/or particle phases; display a large range of volatilities; experience varying deposition velocities, including in some cases revolatilization; and are emitted from a wide variety of sources at a large variety of different scales. In addition, concentrations of air toxics are needed by regulators for both short (days) as well as long (up to a year) time scales. These requirements challenge our current capabilities in air quality models far beyond the needs for other pollutants, such as ozone. The specific work being done under this task involves 1.) developing and testing chemical mechanisms which are appropriate for describing the chemistry of air toxics; 2.) incorporating these chemical and physical mechanisms into EPA's CMAQ modeling system and applying the model at a variety of scales; and 3.) developing the methods for using models to predict HAPs concentrations at subgrid or neighborhood scales; and 4.) using these tools to assess the magnitude and variability of concentrations to which urban populations are exposed.
Description:
Prior to September 11, 2001 developments of Computational Fluid Dynamics (CFD) were begun to support air quality applications. CFD models are emerging as a promising technology for such assessments, in part due to the advancing power of computational hardware and software. CFD simulations have the potential to yield more accurate solutions than existing regulatory air quality models because CFD mechanistically is a solution of the fundamental physics equations and include the effects of detailed three-dimensional geometry and local environmental conditions. This presentation reviews CFD developments and applications to help understand the dust cloud on September 11, 2001 and transport of potential emissions from "ground zero" over the following weeks at the New York World Trade Center (WTC) area. Much has been learned and developed over the past few years through research and development. Herein developments and applications supporting US Environmental Protection Agency's (EPA) WTC program to understand the transport of potential contaminants are summarized to illustrate what has been done and to characterize remaining challenges. There are three major reports being prepared to fully report the work