Evaluation of the CFAST and FDS Fire Models for Multi-Level Fire Scenarios in Large Halls (ICFMP Benchmark Exercise # 2), Deytec, Inc. USA Technical Report No. 2009-04, November 2009.
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Abstract
The analysis presented in this report was conducted for Benchmark Exercise # 2, Part II in the International Collaborative Fire Model Project (ICFMP). The analysis was conducted with Consolidated Model for Fire and Smoke Transport (CFAST) Version 3.1.7, a zone model, and Fire Dynamics Simulator (FDS) Version 2, a computational fluid dynamic model developed by the Building Fire Research Laboratory (BFRL), National Institute of Standards and Technology (NIST). The U.S. Nuclear Regulatory Commission (NRC) is evaluating the CFAST and FDS fire models developed by the National Institute of Standards and Technology for use in NRC’s
regulatory framework. The objective of the second benchmark exercise was to examine scenarios that are more challenging for zone models, in particular to the spread of hot gases from a fire in multi-level large volumes. The fire scenarios have been kept simple in order to allow an evaluation of the physics and performance of the sub-models. The issues examined are a subset
of those that will be faced by modelers simulating fires in turbine halls, auxiliary buildings and containments in nuclear power plants. FDS, including its output processor Smokeview, provides a useful tool to examine the phenomena involved in the scenarios, specifically for examining the flow patterns through the hatches and ventilation systems. The trends of the results from FDS show that the code contains the physics and is capable of simulating the complex flow patterns through vertical hatches. However, modeling vertical flow through horizontal vents using the simple correlations in CFAST is questionable. Experimental data for adequately validating the codes for multi-level scenarios is lacking. Therefore, bounding analyses of such scenarios with a
zone model is recommended until validation exercises are conducted for the codes.
Report: 67 pages.
The analysis presented in this report was conducted for Benchmark Exercise # 2, Part II in the International Collaborative Fire Model Project (ICFMP). The analysis was conducted with Consolidated Model for Fire and Smoke Transport (CFAST) Version 3.1.7, a zone model, and Fire Dynamics Simulator (FDS) Version 2, a computational fluid dynamic model developed by the Building Fire Research Laboratory (BFRL), National Institute of Standards and Technology (NIST). The U.S. Nuclear Regulatory Commission (NRC) is evaluating the CFAST and FDS fire models developed by the National Institute of Standards and Technology for use in NRC’s
regulatory framework. The objective of the second benchmark exercise was to examine scenarios that are more challenging for zone models, in particular to the spread of hot gases from a fire in multi-level large volumes. The fire scenarios have been kept simple in order to allow an evaluation of the physics and performance of the sub-models. The issues examined are a subset
of those that will be faced by modelers simulating fires in turbine halls, auxiliary buildings and containments in nuclear power plants. FDS, including its output processor Smokeview, provides a useful tool to examine the phenomena involved in the scenarios, specifically for examining the flow patterns through the hatches and ventilation systems. The trends of the results from FDS show that the code contains the physics and is capable of simulating the complex flow patterns through vertical hatches. However, modeling vertical flow through horizontal vents using the simple correlations in CFAST is questionable. Experimental data for adequately validating the codes for multi-level scenarios is lacking. Therefore, bounding analyses of such scenarios with a
zone model is recommended until validation exercises are conducted for the codes.
Report: 67 pages.