Fire Simulation for Engineers/FDS

Simple example of fire simulation with FDS

What are FDS and Smokeview?

Fire Dynamics Simulator (FDS) is a computational fluid dynamics (CFD) model of fire-driven fluid flow. The model 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. The partial derivatives of the conservation equations of mass, momentum and energy are approximated as finite differences, and the solution is updated in time on a three-dimensional, rectilinear grid. Thermal radiation is computed using a finite volume technique on the same grid as the flow solver. Lagrangian particles are used to simulate smoke movement, sprinkler discharge, and fuel sprays.

Smokeview is a companion program to FDS that produces images and animations of the results. Smokeview is able to visualize fire and smoke in a fairly realistic way. Via its three-dimensional realistic renderings, Smokeview is an integral part of the physical model, as it allows one to assess the visibility within a fire compartment in ways that ordinary scientific visualization software cannot.

The first version of FDS was publicly released in February 2000. FDS is free and its source code is in the public domain.

Engineering applications

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.

It is generally recognized that FDS can be effectively used in engineering applications to model the following phenomena:

• Low speed transport of heat and combustion products from fire;
• Radiative and convective heat transfer between the gas and solid surfaces;
• Sprinkler, heat detector, and smoke detector activation.

FDS can be used to model the following problems, too:

• Pyrolysis;
• Flame spread and fire growth;
• Sprinkler sprays and suppression by water.

Currently, the users interested in engineering applications should probably avoid using FDS to model the latter problems, as they are still subject to intense research study in academic environments.

To date, about half of the applications of the model have been for design of smoke control systems and sprinkler/detector activation studies. The other half consist of residential and industrial fire reconstructions.

Who develops FDS?

Currently, FDS is maintained by the Building and Fire Research Laboratory (BFRL) of National Institute of Standards and Technology. The developers at NIST have formed a loose collaboration of interested stakeholders, including:

• VTT Technical Research Centre of Finland, a research and testing laboratory similar to NIST;
• The Society of Fire Protection Engineers (SFPE);
• Fire protection engineering firms that use the software;
• Engineering departments at various universities with a particular emphasis on fire.

Who uses FDS?

The use of fire models currently extends beyond the fire research laboratories into the engineering, fire service and legal communities.

FDS is intended for use only by those competent in the fields of fluid dynamics, thermodynamics, heat transfer, combustion, and fire science, and is intended only to supplement the informed judgment of the qualified user. The software package is a computer model that may or may not have predictive capability when applied to a specific set of factual circumstances. Lack of accurate predictions by the model could lead to erroneous conclusions with regard to fire safety.

Sufficient evaluation of any model is necessary to ensure that users can judge the adequacy of its technical basis, appropriateness of its use, and confidence level of its predictions.

Inside FDS

• Features
• Limitations
• Running FDS

Prescribing the input file

• Input file basics
• General configuration
• Combustion
• Radiation
• Computational domain
• Materials
• Extra gas species
• Lagrangian particles
• Boundary conditions
• Solid geometry
• Devices and control logic
• Output

Real world examples

• Building a ventilator
• Prescribing a simplified burning material
• Simulation and revelation of smoke of a smoldering fire
• A pan filled of ethanol
• A simple parking lot
• A simple building