You are here:
Urban Dispersion Studies at the EPA
Citation:
Pirhalla, M., D. Heist, S. Perry, W. Tang, AND L. Brouwer. Urban Dispersion Studies at the EPA. University of Arkansas Chemical Engineering Department Seminar, Fayetteville, AR, March 31, 2022.
Impact/Purpose:
This presentation highlights some of the recent urban dispersion research conducted within US EPA's Fluid Modeling Facility (FMF) Meteorological Wind Tunnel (MWT). The presentation provides an overview of the recent Jack Rabbit II project simulated within the wind tunnel and through fine scale large eddy simulation (LES) modeling. The presentation also demonstrates EPA's research facilities and capabilities at the Research Triangle Park campus, which may be of interest to some external university scientists and engineers. Plans for a future research project are also be presented.
Description:
The US Environmental Protection Agency (EPA) is tasked with protecting human health and the environment, which also includes remediating indoor and outdoor areas following wide-area chemical, biological, radiological, or nuclear (CBRN) events. The Homeland Security Research Program (HSRP) within EPA is interested in refining tools and methods to better understand the fate and transport of hazardous contaminants through all phases of the emergency response process. Considerable interest and uncertainty arise when an effluent is released within or near urban areas. Dense and irregular building morphologies within these settings create complex turbulence, dispersion, and flow regimes that affect downwind and ground level pollutant concentrations. This talk details some of the urban dispersion studies recently completed within EPA’s Fluid Modeling Facility (FMF) meteorological wind tunnel. Our most recent project leveraged data from a Special Sonic Study that was part of the Jack Rabbit II (JRII) field study. JRII was conducted at Dugway Proving Ground (DPG), UT, where large releases of chlorine gas were dispersed within an array of CONEX shipping containers. During the Special Sonic Study, flow and turbulence around the obstacles were measured from a network of 30 sonic anemometers distributed around the CONEX array. In our project, a 1:50 scaled model of the JRII test area was constructed and simulated within EPA’s wind tunnel to thoroughly examine the complex flow and dispersion patterns. Unlike the dense gas used in the field study, a neutrally buoyant tracer was released, and concentrations were gathered with a hydrocarbon analyzer (HCA) system. To complement the study, Embedded Large Eddy Simulation (ELES) experiments and AERMOD dispersion model runs were also produced. Results indicated that the initial plume dispersion depended strongly on the structures immediately adjacent to the release and that slightly oblique incoming wind directions caused additional off-axis channeling of the plume, which demonstrates that building structures can cause considerable plume drift, especially under greater incoming wind obliquity. The talk will also touch on an urban-related study that is currently in progress at the FMF.