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Fire Dynamics Simulator (Version 4): Technical Reference Guide.


pdf icon Fire Dynamics Simulator (Version 4): Technical Reference Guide. (683 K)
McGrattan, K. B.

NIST SP 1018; NIST Special Publication 1018; 109 p. March 2006.

Keywords:

dynamics; simulation; scenarios; hydrodynamic model; combustion; thermal radiation; sprinklers; validation; sensitivity

Abstract:

The use of fire models currently exteI1lds beyond the fire research laboratories and into the engineering, fire service and legal communities. Surveys of available fire models have been compiled and show a significant increase in the number of available models over the last decade. Sufficient evaluation of fire models is necessary to ensure that those using the models can judge the adequacy of their technical basis, appropriateness of their desired use, and confidence level of their predictions. This document provides the theoretical basis for the Fire Dynamics Simulator (FDS) and a summary of the work performed to verify and validate the model. Such evaluations of fire models prevent their unintentional misuse. This guide is based in part on the "Standard Guide for Evaluating the Predictive Capability of Deterministic Fire Models," ASTM E 1355. ASTM E 1355 defines model evaluation as "the process of quantifying the accuracy of chosen resu1ts from a model when applied for a specific use." The model evaluation process consists of two main components: verification and validation. Verification is a process to check the correctness of the solution of the governing equations. Verification does not imply that the governing equations are appropriate; only that the equations are being solved correctly. Validation is a process to determine the appropriateness of the governing equations as a mathematical model of the physical phenomena of interest. Typically, validation involves comparing model results with experimental measurement. Differences that cannot be explained in terms of numerical errors in the model or uncertainty in the measurements are attributed to the assumptions and simplifications of the physical model. Evaluation is critical to establishing both the acceptable uses and limitations of a model. Throughout its development, FDS has undergone various forms of evaluation, both at NIST and beyond. This guide provides a survey of work conducted to date to evaluate FDS. Roughly half of the referenced studies were aimed primarily at model evaluation, the other half describe limited work to validate FDS for a specific use. The latter group were performed mostly by practicing engineers who did not have the time or resources to comprehensively evaluate the model. Collectively, the body of work forms the basis of a model evaluation. As FDS development continues, the work performed to date will provide a framework for future research.