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BREEZE DEGADIS Dense Gas Disperison Modeling SoftwareDEGADIS

BREEZE HAZ DEGADIS, a software package for modeling the consequences of an accidental chemical release resulting in a denser-than-air plume. This package includes the DEGADIS dispersion model, developed by Tom Spicer and Jerry Havens of the University of Arkansas, upon commission by the U.S. Coast Guard, and a proprietary source-term model called EXPERT.

DEGADIS is a dense-gas dispersion model that can be used to determine downwind distances to hydrocarbon flammability levels and toxic gas concentrations from accidental release scenarios.  Source types include evaporating pools and ground-level gaseous or aerosol release scenarios.  This version of DEGADIS also incorporates the vertical jet plume model developed by Ooms, Mahiu, and Zelis.  The jet plume is useful for modeling chemicals stored under pressure which, if released, produce high velocity emissions.  The Ooms jet plume model estimates the trajectory and dilution of these types of vertically oriented gas or aerosol jets.  It also accounts for ground reflection when the plume's lower boundary reaches ground level and predicts the ensuing ground level plume dispersion.

EXPERT is a source-term model that is used to calculate certain source parameters, such as evaporation rate, pool radius, or release duration, that are needed to run the DEGADIS model.  EXPERT automatically calculates the required source-term parameters and seamlessly transfers the results to DEGADIS, where they are used as model input.


BREEZE HAZ DEGADIS offers many features to tailor your analyses to a wide variety of sources and release scenarios.

Release Scenarios...models a variety of release scenarios, including: gas and aerosol releases; continuous, instantaneous, finite duration, and time-varying releases; ground-level low-momentum area releases; ground-level or elevated vertical jet releases.

Heat Transfer... includes a non-isothermal option which uses an energy balance approach to determine cloud temperature (density), as surrounding air is mixed into the dense cloud.  This approach provides heat transfer options over both land and water.  Alternatively, DEGADIS provides an isothermal option, which uses adiabatic (no heat transfer) calculations to determine the liquid and vapor contents of an aerosol mixture.

Receptors... calculates plume concentration at model-selected downwind receptor distances. The model run commences when one-half of the lowest specified concentration is reached.  DEGADIS also features nloannovative tool that provides the concentration time-history at one or more receptors subsequent to an instantaneous or finite duration model run.

Chemical Property Data...contains a database of over 150+ common industrial chemicals. The program includes the capability to add and store new chemicals or modify existing chemical data.

Toxicity Data... includes chemical toxicity data, including the Toxic Endpoint, IDLH (Immediately Dangerous to Life and Health), TLV-TWA (Threshold Limit Value - Time Weighted Average), and TLV-STEL (Threshold Limit Value - Short Term Exposure Limit) values, where available, for each chemical.

Meteorological Data...estimates stability class using site characteristics, date and time of release, and user-specified cloud cover, cloud type, and wind speed observations or the stability class can be entered directly. The model simulates one set of meteorological conditions, and is applicable for averaging periods of 1-hour or less.