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WIND-TUNNEL SIMULATIONS TO ASSESS DISPERSION AROUND THE WORLD TRADE CENTER SITE
Citation:
Snyder, W H., D K. Heist, S G. Perry, R S. Thompson, AND R E. Lawson Jr. WIND-TUNNEL SIMULATIONS TO ASSESS DISPERSION AROUND THE WORLD TRADE CENTER SITE. Presented at International Workshop on Physical Modeling of Flow and Dispersion Phenomena, Prato, Italy, September 3-5, 2003.
Impact/Purpose:
The objective of this task is to develop and evaluate numerical and physical modeling tools for simulating ground-level concentrations of airborne substances in urban settings at spatial scales ranging from ~1-10 km. These tools will support client needs in the areas of air toxics and homeland security. The air toxics tools will benefit the National Air Toxics Assessment (NATA) program and human exposure modeling needs within EPA. The homeland security-related portion of this task will help in developing tools to assess the threat posed by the release of airborne agents. Both sets of tools will consider the effects induced by urban morphology on fine-scale concentration distributions.
Description:
A wind-tunnel study was conducted of dispersion from the site of the destroyed World Trade Center (WTC) in New York City. A scale model of lower Manhattan, including a scaled representation of the rubble pile, was constructed. The first phases of the study involved smoke visualization and measurements of flow patterns with winds from the west; the second phase involved the measurement of dispersion patterns resulting from tracer releases from the rubble pile. Neither the initial explosions nor the collapses of the towers have been simulated but, instead, dispersion from the smoldering rubble pile was modeled for the time period around two to six weeks after the catastrophe.
Notable features included: strong horizontal recirculation patterns caused by a group of tall buildings not directly downwind acting as a single obstacle, vertical recirculation caused by a tall upwind building resulting in "pumping" of contaminants up the lee side to heights above the building top, and consistent alignment of flow directions with the street canyon axes at the lower levels, tending toward free-stream values at the upper elevations.
This research has been supported by the US Environmental Protection Agency. It has been subjected to agency review and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use