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Smoke Detector Algorithm for Large Eddy Simulation Modeling.


pdf icon Smoke Detector Algorithm for Large Eddy Simulation Modeling. (944 K)
Roby, R. J.; Olenick, S. M.; Zhang, W.; Carpenter, D. J.; Klassen, M. S.; Torero, J. L.

NIST GCR 07-911; 50 p. July 2007.

Sponsor:

National Institute of Standards and Technology, Gaithersburg, MD

Keywords:

smoke detectors; algorithms; simulation; smoke detection; time lag; detector response; response time; fire models; sensitivity; smoke movement; validation; computational fluid dynamics; UL 217; equations; fire tests; scenarios

Abstract:

This study chronicles the development and integration of a smoke detector activation algorithm that describes the response time of a smoke detector into a Large Eddy Simulation (LES) fire model. Although the activation algorithm could be used with any CFD smoke movement model, the results here address specificaLly its application to the Fire Dynamics Simulator (FDS). The fire model predicts the smoke concentration and velocity adjacent to the detector while an algorithm based on characteristic velocity-based lag times describes the transport of smoke into the sensing chamber of the smoke detector. An Underwriters Laboratories Standard 217 fire test, as well as experimental data from two experimental multi-room compartment fires, were used for comparison and validation of the accuracy of the algorithm. A series of benchmark studies in a numerical wind tunnel provided a mechanism to establish the sensitivity of the model to the different input parameters. The algorithm was found to be very accurate in determining detector activation tunes for both high and low-velocity smoke flows. Additionally, it was found that the algorithm provides more accurate smoke detector activation times than other correlations based on optical density or temperature. The activation algorithm will be included in the next release of FDS (version 5.x).