CFD Research Corporation has been developing an advanced simulation capability for urban area CBRN/E transport and dispersion modeling in coordination with the Defense Threat Reduction Agency's Consequence Assessment Branch/TDOC. This on-going work has resulted in a software suite (CFD-Urban) which is augmented with our in-house analysis capability to model and simulate the wind, turbulence and dispersion fields in urban areas on the building to city block scale.

Oklahoma City Central Business District: Joint Urban 2003 Field Test Support

Concentration Iso-Surfaces of Simulant Illustrating Channeling and Vertical Mixing Inherent in Urban Areas (Click to Play 11mb)

The state-of-the-art capability represented by CFD-Urban is its ability to directly model such important features as channeling, lofting, vertical mixing and turbulence. Since CFD-Urban is based upon a multi-physics/multi-disciplinary commercial software suite (CFD-ACE+) the incorporation of important physical models, such as thermal effects, gas-phase chemistry and two-phase flow processes, is easily accomplished. As an example, consider the animation shown below, where a hypothetical chemical agent is released from a moving car.

Chemical Agent Relased from a Moving Vehicle (Click to Play 8.8mb)

Validation and Verification

CFD-Urban has recently completed an in-depth Validation and Verification study where results have been statistically compared to a series of well-known and accepted field tests. The results of this study were presented at the 8th Annual George Mason University Conference on Transport and Dispersion Modeling. The presentation made there is available here for download.

Kit Fox Field Test: Equivalent Roughness Pattern (ERP) and Sampler Locations	Mock Urban Setting Test (MUST): Shipping Containers, Release Locations (red) and Sampler Locations (green)

CFD-Urban Features

The features of CFD-Urban that prove useful for modeling the transport and dispersion of Chemical and Biological substances in urban areas include:

CBRN/E T&D Modeling Capability

Through this work, we are uniquely qualified to apply our state-of-the-art simulation capability to support the protection of urban areas, high value civilian buildings and complexes, as well as military bases. As evidenced by our recent work shown below with DTRA, NCAR and DHS, we are able to provide timely and high-quality hazards predictions for important National Security Special Events (NSSE), force protection projects and field tests. Examples of our recent applications of this expertise includes the following.

Pentagon Shield: Pentagon Force Protection

CFDRC is working with the National Center for Atmospheric Research (NCAR) under a subcontract with the Defense Advanced Research Projects Agency (DARPA) to protect the Pentagon through the use of coupled, operational weather and dispersion models. CFDRC has proposed to integrate our advanced Computational Fluid Dynamics model with the NCAR VLAS system to provide near-real-time dispersion behavior on-demand to the Pentagon Force Protection Agency.
Related Web Site: www.rap.ucar.edu/projects/shield/

Lidar Data (above left), flow predictions (above right), in support of the Pentagon Shield Project.

Joint Urban 2003 Field Test

In the spring of 2003, CFDRC worked closely with the science team for the Joint Urban 2003 Field Test, by providing predictive (before test) simulations of the transport and dispersion behavior of the downtown Central Business District Area of Oklahoma City. Based upon our detailed simulations before the test, the science team repositioned sensors to capture the extensive vertical mixing and channeling behavior that we predicted and were observed in the test. Related Web Site: http://ju2003.pnl.gov

Tracer gas concentration iso-surfaces for two different release locations (Click Image to Play 10mb)

Dispersion Footprints in the OKC CBD for Different Release Scenarios

Urban 2000 Field Test/VTMX: Salt Lake City

As part of our Verification and Validation study, we have performed dispersion simulations in the Salt Lake City CBD for comparisons to data taken during the Urban 2000 Field Test. Simulations have been made for 3 of the 10 Intensive Operating Conditions (IOP's), of which the animation below shows the unsteady dispersion behavior arising during IOP 10

SLC Unsteady Dispersion (Click to Play 7mb)

BNL Urban Dispersion Program and Madison Square Garden Test (MSG04)

CFDRC is presently supporting DHS through DTRA for the Madison Square Garden Urban Dispersion Program, and the MSG04 field test. We are simulating the transport and dispersion of tracer gas released from 5 different locations around Madison Square Garden, and tracking this dispersion through the nearby environs. The figures below show preliminary results from our calculations.

Unsteady ground level concentrations of tracer gas for New York City, in support of the MSG04 Field Test.(Click to Play 14mb)

Close-up views of predicted velocity field at street level (left) and ground level concentrations (right)