Re: Validation of FDS Sprinkler Activation Times Predictions

[FPESC...@aol.com]

Ladies and Gentlemen-

 

I am reviewing a research paper where the FDS has been used to predict the activation times of multiple sprinklers in a wet pipe sprinkler system.  In a paper titled "Interaction of Sprinklers With Smoke and Heat Vents" dated February 1999, Craig Beyler and Leonard Cooper state the following with respect to the use of fire models based upon CFD to predict the activation times of multiple sprinklers:

 

"While there have been many attempts to model all or part of the interactions of sprinklers and vents, the issues are more complex than can be dealt with using even the most sophisticated modeling methods available today. The most clear indication of this is the recent NFPRF research project [1997/1998]. While modeling of the fluid mechanical aspects of the problem were quite successful in predicting aspects of sprinkler activation in the first heptane spray fire series, the model was unable to predict the corresponding results in the rack storage tests beyond first sprinkler activation."  (Page 18 of the Beyler/Cooper paper.)

 

Have the capabilities of the FDS to accurately predict the activation times of multiple sprinklers been significantly improved since February 1999?

 

Is the latest FDS capable of accurately predicting the activation times of multiple sprinklers?

 

Has the capability of the FDS to predict the activation times of multiple sprinklers been sufficiently validated so that it can be stated without any reservations that this FDS capability has been validated?

 

I would appreciate your comments and opinions regarding the above.

 

Richard Schulte

Schulte & Associates

Building Code Consultants

Chicago/New Orleans

fpesc...@aol.com

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[Kevin]

Work performed by NIST and others to assess the accuracy of FDS is
documented in

http://fds-smv.googlecode.com/svn/trunk/FDS/trunk/Manuals/All_PDF_Files/FDS_5_Validation_Guide.pdf

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[Kevin]

This is a continuation of the dialog from a second thread. It is
redirected here for clarity -- Kevin


Richard Schulte writes:


The response really doesn't answer the three questions posed. I
have
reviewed the Validation Guide in great detail prior to posing the
questions.


Does the fact that data is published in the Validation Guide mean
that the
capabilities of the FDS has been validated without any limitations?
The data
published in the Validation Guide only addresses fires generated by
heptane
spray burners? Are fires in heptane spray burners representative of
fires
which occur in the "real world"?


It is my opinion that validation of the FDS capabilities to
accurately
predict the activation times of multiple sprinklers based upon the
data presented
in the Validation Guide is limited to fires generated by heptane
spray
burners, but does not validate the FDS capability to predict
sprinkler activation
times in "real world" arrays of combustibles. (In other words, I
concur with
Dr. Beyler's statement in his paper dated February 1999.) Is my
understanding
of the limitation on validation correct?

[Kevin]

The following text is taken from Chapter 1 of the FDS Validation
Guide:

Although there are various definitions of model validation, for
example those contained in ASTM E 1355 [2],
most define it as the process of determining how well the mathematical
model predicts the actual physical
phenomena of interest. Validation typically involves (1) comparing
model predictions with experimental
measurements, (2) quantifying the differences in light of
uncertainties in both the measurements and the
model inputs, and (3) deciding if the model is appropriate for the
given application. This Guide only does
(1) and (2). Number (3) is the responsibility of the model user.

A common question asked of any mathematical model is whether it is
validated. To say that FDS is
“validated” means that the model has been shown to be of a given level
of accuracy for a given range of
parameters for a given type of fire scenario. Although the FDS
developers continuously perform validation
studies, it is ultimately the end user of the model who decides if the
model is adequate for the job at hand.
Thus, this Guide provides the raw material for a validation study, but
it does not and cannot be considered
comprehensive.