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Performance Testing of Fire Protection Systems in Tunnels: Integrating Test Data with CFD Simulations
Published:  14 April, 2010

This paper discusses the dynamic nature of very large fire tests that were conducted in a tunnel test facility in San Pedro de Anes in Spain in 2006, and describes highlights of the FDS4 simulation of one of five tests that were simulated. The high cost of conducting large, full-scale fire tests for the evaluation of active fire suppression systems in tunnels tends to limit both the extent of the instrumentation provided and the number of tests that are conducted. Because of the turbulent complexity of large test fires in tunnels, performance criteria based on single point measurements derived from experience with much smaller test fires are not reliable measures of the overall benefits of the system. A means was sought to reduce the reliance on single point instrumentation readings, and to augment the value of the limited amount of test data by integrating the field testing with CFD modeling.

In this study the NIST Fire Dynamics Simulator version 4 (FDS4), a computational fluid dynamic (CFD) model, was used to simulate a series of full-scale fire tests of water mist systems conducted in a test tunnel. The objective was to show that the CFD simulations could be at least partially validated by demonstrating a reasonable degree of agreement with the conditions measured in the tests. The model could then be used to evaluate the performance of the water mist system under conditions that were not tested. The level of agreement between the fire tests results and the results of the simulation was deemed to be good enough to establish confidence in applying the model to examine the conditions that would occur with an unsuppressed fire, which had not been tested.