NIST Grant Awarded to Develop Standard Guide for Fire Model Input Parameters

[Kevin]

For some time now it has become painfully obvious that there is no
standardized way of obtaining all of the parameters you need to run
FDS.
This is especially true of materials that burn. There are various
devices
that you can use to measure various properties, but there is no
consensus on
the exact physical and mathematical description of these, and thus, no
standard way of taking benchscale data and converting it into an FDS
input
file. If you search the FDS Discussion Group you will see many
exchanges
that demonstrate the problem.

Our approach to solving this problem has two fundamental components.
First,
we're trying to improve the description of the gas phase, mainly the
fire
itself, to reduce the current level of grid sensitivity. We cannot
make
progress on the materials problem if we cannot be assured of a fairly
accurate, relatively grid-insensitive heat flux to the solid surface.
Second, we need to have a common understanding of the solid phase,
both
mathematical and physical. Simo Hostikka wrote a fairly general
description
of multi-layered, multi-component, multi-reaction solids into FDS 5,
but now
where do we get all those parameters? Improved physics means more
experimental measurements. How do we get them?

The Building and Fire Research Lab at NIST has a small grants program,
and
recently Nick Dempsey of WPI, Marc Janssens of Southwest Research, and
Morgan Hurley of the SFPE were awarded a three year grant to develop
an
engineering guide that will document the standard test methods used to
obtain material properties, and more importantly the physical and
mathematical interpretation of these methods that will enable us all
to
understand what to do with measurements made in the various benchscale
devices. As the project starts, more information will become available
about
it. For now, I'd like to remind you that at the upcoming IAFSS
meeting in
Germany, Nick Dembsey and Simo Hostikka are hosting a workshop on
Sunday,
September 21, to discuss the materials issue, and Nick can at that
time
provide more information about the project. If you can make it, great.
If
not, there will be opportunity, via our Discussion Group, to stay
abreast of
progress.

[SkyW]

Hi,

I fully agree that this is one of the major works to be done and it
will be great if we can finally have a public validated table with all
the input parameters to describe combustibles and fires. I believe
it's specially important if we want FDS to be a widely use enfineering
tool. I'm personally involved in water mist system design and my goals
are related to fire supression. Usually I use FDS to reduce expensive
real fire tests. Of course at this stage I still need at the end to
validate designs with real fire tests but at least I'm able to reduce
the amount.

First problem I had to face was to properly describe fires. It was
really hard to get all physical parameters needed to describe fire
(emissivity, absoprtion factors, ..) specially when those parameters
are many time dependent of wave lenght, temperature, ... which at the
end have to be translated to a single "total" value. Also grid size
effect, which is very important, may impose a too small cell size
which is impossible to manage when trying to simulate a real scenario
in "normal" pc's.

I had to forget all the physic meaning of these parameters and I
focused this problem from a more engineering point of view. I
previously selected a suitable grid size and I simulated fires (at the
moment heptane and diesel pool fires) adjusting the parameters
(specially emissivuty and absoprtion coefficient) until fire heat
release fitted to real cone calorimetry measurements I've found in
literature (SP have publish several results).

Of course I'm open to share my results and I hope these new projects
will end up successfully.

Regards

SkyW

[Bryan Klein]

Where are we on this project now?

-Bryan

[Khalid Moinuddin]

Hi Kevin,

These are what I have been saying over last few years. Unless we solve these two fundamental issues, all other complex features can't be much useful. Despite having new LES models for FDS6, grid sensitivity has not been improved. We found that with FDS5 for solid fuel burning (cone calorimeter simulation), we need grid cells of 5 mm to obtain grid independent result. It is found to be the same for FDS6. For liquid fuel, with FDS5 we couldn't obtain grid independent result despite using supercomputers. With solid phase pyrolysis there are so many variations with input parameters - depending on temperature, heating rate, radiation flux etc.

We have been in principle awarded a research grant over three years to use/improve WFDS (3D physics based modelling) for bushfire simulation - as next generation fire prediction model. These two areas are on top of our list. Other areas we would like to concentrate on are improved parallel programming, adaptive mesh refinement and fire brand model. We are expecting to have one postdoc and three PhD students. If you (especially Kevin, Ruddy, Randy and Simo) can suggest some names via my personal email - that will be great!

Regards,

Khalid

---

From: fds...@googlegroups.com [fds...@googlegroups.com] on behalf of Bryan Klein [kl...@thunderheadeng.com]
Sent: Thursday, 5 September 2013 4:30 PM
To: fds...@googlegroups.com
Subject: [fds-smv] Re: NIST Grant Awarded to Develop Standard Guide for Fire Model Input Parameters

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