Modeling Software for EHS Professionals

DEGADIS Model

DEGADIS is an EPA approved dense-gas model that predicts downwind vapor concentrations for explosion hazards, developed specifically to model heavier-than-air gaseous releases. A cloud from a dense gas release behaves very differently than a plume from a lighter-than-air release. Since the gas is heavier than air, the cloud characteristics are primarily gravity-driven. Negative buoyancy and stable density stratification are among the factors that prevent the application of a Gaussian dispersion model from accurately simulating a dense gas release.

DEGADIS can model a mixture of release type and duration scenarios:

  • Ground-level release type: continuous, finite, and transient durations
  • Vertical Jet release type: continuous and finite durations
  • Evaporating liquid spill release type: continuous, finite, and instantaneous durations

Release Durations

  • Continuous Release: A continuous release is a steady-state release of dense gas at a constant rate into the atmosphere over a long period of time. As a rule, any release that is greater than 1,000 minutes is modeled as a continuous release. The output from modeling a steady-state release is concentration estimates at various downwind distances determined by the model.
  • Finite Duration: A finite duration release is a steady-state release of dense gas at a constant rate into the atmosphere over a short period of time. As a rule, any release that occurs over a period of less than 1,000 minutes is modeled as a finite duration release. Finite duration model output is organized either by time or distance, depending on which parameter is of greater interest.
  • Transient Release: A transient release varies over time; for example, if a liquid pool boils off or a container of gas depressurizes. As the pool decreases in size, the emission rate and radius change. Other transient releases include near-instantaneous releases such as container ruptures. Transient modeling output is organized either by time or distance, depending on which parameter is of most interest.

Release Method

  • Vertical Jet Release: A jet release is a vertical release of a dense gas or aerosol. The simulation uses the Ooms mathematical model for a dense gas jet plume. The jet plume model requires that the jet be vertical, with a definable exit velocity. If the jet release is such that the plume centerline does not reach the ground before dispersing, the jet plume model is run alone. If this is unclear, or if the plume centerline does reach the ground, the jet plume model is run in conjunction with the regular DEGADIS model as either a continuous or finite duration release.
  • Liquid Spill: A liquid spill is the release of a chemical in its liquid state. The liquid is assumed to form a pool at ground level, with the evaporation rate calculated using one of three different evaporation models incorporated into DEGADIS. The results from the evaporation model are run in the DEGADIS model as either a continuous or finite duration release.

 

LFG DEGADIS chart screenshot

A graph of the centerline concentration at the height of interest, which users can generate after successfully running the DEGADIS model.

LFG DEGADIS output screenshot

For plotting results on the base map, users can specify the concentration contours and output file.

Priced at $3,995

Includes one year of maintenance with purchase.

Buy Now
Questions?
Upcoming Training
view 5 more courses >>