v7.7.2 ventilation limited fire does not extinguish

[DavidB]

Hello,

We have identified an error in CFAST 7.7.2 which is causing vent limited scenarios (long duration small fires in enclosed spaces) to behave in an unphysical manner. Specifically the fire does not reduce HRR / extinguish. The CFAST tool itself appears to run as normal and no errors are identified during running.

The problem occurs (in v7.7.2) when the fire compartment is connected to other compartments (via wall / ceiling vents) and none of the compartments has an opening to atmosphere (Outside). The problem does not occur when the fire compartment is standalone, i.e. not connected to other compartments.

This issue is not present in the latest CFAST (v7.7.4) and a check using Thornton’s rule indicates that the results from v7.7.4 are credible.

I assume it was something identified either when going to 7.7.3 or to 7.7.4 and this resolved it. I am raising this here to see if someone can confirm that this issue was identified or can be explained by previous updates to the tool. Can anyone advise?

Thanks.

[Kevin McGrattan]

This is a link to the CFAST release notes.

https://github.com/firemodels/cfast/wiki/Release-Notes

These noted code fixes often address issues like yours even though it is often difficult to understand how. Often the fix addresses some issue related to global and local pressure effects that affect vent flow.

[Glenn Forney]

it is likely this commit was the one that fixed the problem.  paul can comment when he gets back

Jan 13, 2023 b364384b preneke CFAST: Updating calc of pressure across vents to outside

--
You received this message because you are subscribed to the Google Groups "CFAST" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cfast+un...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/cfast/CAAJimDF9HGCx5r9kY4RN3RAyN32aDb03AumLGN5LbkpRicCuXw%40mail.gmail.com.

--

Glenn Forney

[DavidB]

OK, thanks both. As i noted, the problem is not present in the latest version so probably not worth dwelling on!  Kevin, I agree that it is difficult to interpret the release notes and how they might affect a scenario. Glenn, it would be interesting to hear back, but only for interest, it is not affecting a project (for me at least).