Fire Dynamics Simulator (FDS) is a computational fluid dynamics (CFD) model of fire-driven fluid flow. 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.
FDS is free software developed by the National Institute of Standards and Technology (NIST) of the United States Department of Commerce, in cooperation with VTT Technical Research Centre of Finland. Smokeview is the companion visualization program that can be used to display the output of FDS.
The first version of FDS was publicly released in February 2000. To date, about half of the applications of the model have been for design of smoke handling systems and sprinkler/detector activation studies. The other half consist of residential and industrial fire reconstructions. Throughout its development, FDS has been aimed at solving practical fire problems in fire protection engineering, while at the same time providing a tool to study fundamental fire dynamics and combustion.The other half consist of residential and industrial ﬁre reconstructions. Throughout its development, FDS has been aimed at solving practical ﬁre problems in ﬁre protection engineering, while at the same time providing a tool to study fundamental ﬁre dynamics and combustion.
Hydrodynamic Model FDS solves numerically a form of the Navier-Stoke sequations appropriate for low speed, thermally-driven ﬂow with an emphasis on smoke and heat transport from ﬁres. The core algorithm is an explicit predictor-corrector scheme, second order accurate in space and time. Turbulence is treated by means of Large Eddy Simulation (LES). It is possible to perform a Direct Numerical Simulation (DNS) if the underlying numerical mesh is ﬁne enough. LES is the default mode of operation.
Combustion Model For most applications, FDS uses a single step, mixing-controlled chemical reaction which uses three lumped species (a species representing a group of species). These lumped species are air, fuel, and products. By default the last two lumped species are explicitly computed. Options are available to include multiple reactions and reactions that are not necessarily mixing-controlled.
Radiation Transport Radiative heat transfer is included in the model via. the solution of the radiation transport equation for a gray gas,and in some limited cases using a wide band model. The equation is solved using a technique similar to ﬁnite volume methods for convective transport, thus the name given to it is the Finite Volume Method (FVM). Using approximately 100 discrete angles, the ﬁnite volume solver requires about 20 % of the total CPU time of a calculation, a modest cost given the complexity of radiation heat transfer. The absorption coefﬁcients of the gas-soot mixtures are computed using the RadCal narrow-band model . Liquid droplets can absorb and scatter thermal radiation. This is important in cases involving mistsprinklers,but also plays a role in all sprinkler cases. The absorption and scattering coefﬁcients are based on Mie theory.
Geometry FDS approximates the governing equations on a rectilinear mesh. Rectangular obstructions are forced to conform with the underlying mesh.
Multiple Meshes This is a term used to describe the use of more than one rectangular mesh in a calculation. It is possible to prescribe more than one rectangular mesh to handle cases where the computational domain is not easily embedded within a single mesh.
Parallel Processing FDS employs OpenMP , a programming interface that exploits multiple processing units on a single computer. For clusters of computers, FDS employs Message Passing Interface (MPI) .
Boundary Conditions All solid surfaces are assigned thermal boundary conditions, plus information about the burning behavior of the material. Heat and mass transfer to and from solid surfaces is usually handled with empirical correlations, although it is possible to compute directly the heat and mass transfer when performing a Direct Numerical Simulation (DNS).