Smoke Detector Algorithm for Large Eddy Simulation Modeling.
Smoke Detector Algorithm for Large Eddy Simulation
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,
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
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).