FDS is a CFD model most widely applied to fire-driven fluid flow, although it can be used for a very wide range of applications. The software solves numerically a form of the Navier-Stokes equations appropriate for low-speed, thermally-driven flow with an emphasis on smoke and heat transport from fires.
Smokeview is a visualization program that is used to display the results of an FDS simulation.
A finite-difference method is used with a rectilinear grid and automatically optimized time-stepping. LES or DNS can be used. A Smagorinsky sub-grid model is used with LES.
All Fortran source code is available.