Industrial Source Complex Model: Algorithms

The ISC models are steady-state Gaussian plume models (see below), and use a variety of algorithms. Basically, the Gaussian plume algorithm is modified to allow for simple point source emissions from stacks and emissions from stacks that experience the effects of aerodynamic downwash due to nearby buildings, isolated vents, multiple vents, storage piles, and conveyor belts. In short,the model looks to provide for those sources that might be present at any industrial complex. The emissions sources can be point source, volume source, area source, and open pit sources.

where
     c(x,y,z) = contaminant concentration at the specified coordinate [ML^-3],
     x = downwind distance [L],
     y = crosswind distance [L],
     z = vertical distance above ground [L],
     Q = contaminant emission rate [MT^-1],
     sy = lateral dispersion coefficient function [L],
     sz = vertical dispersion coefficient function [L],
     u = wind velocity in downwind direction [L T^-1],
     H = effective stack height [L].

The models have a wide range of options available, providing significant flexibility to the air quality analyst. The default algorithms are those that are associated with regulatory modeling options, such as:

stack-tip downwash (downwash that occurs at the top of the stack when the exit velocity of the emissions are too low)
buoyancy-induced dispersion
final plume rise
a routine for processing averages when calm winds occur
default values for wind profile exponents
default values for vertical potential temperature gradients

The models can also calculate properties such as dry and wet deposition, and can be used for complex terrain situations (complex terrain is that modeling area where the terrain is higher than the stack height).

Confused? Have a question? If so, check out the Frequently Asked Questions (FAQ) page or send mail to the OS411 tutor (os411tutor@shodor.org) with your question!

Report technical/content problems here