numerical instability at ~ 2 s when running levelset2.fds with latest fds release

[gforney]

running FDS-6.9.1-843-g8d17db8-master (I believe the latest revision) on spark on the case smv/Verification/WUI/levelset2.fds gives a numerical instability at about 2 s

a 2nd problem that smokebot did not catch the numerical instability error. I only noticed because the image comparison portion of smokebot showed an image that was way different than the base (because the 3D smoke was not being generated). that is a smokebot problem - I'll fix

[gforney]

I did a git bisect. This was the first bad commit.
Author: ericvmueller [email protected]
Date: Tue Aug 20 09:26:53 2024 -0400

FDS Source: update defaults for custom level set fuel model

[ericvmueller]

Okay I'll take a look

[gforney]

thanks. smokebot should now find these errors (now looking for ERROR'1 or more characters': not ERROR:

[marcosvanella]

I'm looking into this. Seems change in parameters is giving an instability in a cut-face.

[gforney]

should I make a change to one ore more of the 'GRASS' parameters. I probably copied them from another case at some point. I am mainly interested in testing visualization not the actual burning behavior

&SURF ID = 'GRASS'
DEFAULT = .TRUE.
VEG_LSET_ROS_HEAD = 1.5
VEG_LSET_ROS_FLANK = 0.48
VEG_LSET_ROS_BACK = 0.15
VEG_LSET_WIND_EXP = 1
RGB=122,117,48
HRRPUA=200.
BURN_DURATION=25. /

[ericvmueller]

Changing the packing ratio (VEG_LSET_BETA) to a lower value will allow it to run... but the current defaults aren't unphysical and it should run. This highlighted an issue with handing the wall stress in cut cells at mesh interfaces which should be more robust (@marcosvanella correct me if I'm wrong)

[rmcdermo]

Is this not in the regular firebot runs? If not, sounds like it should be.

[gforney]

This case is in smokebot. I am testing levelset and agl slice visualization .i can put it in firebot if you like

…

On Mon, Sep 16, 2024, 11:17 AM Randy McDermott ***@***.***> wrote: Is this not in the regular firebot runs? If not, sounds like it should be. — Reply to this email directly, view it on GitHub <#13428 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AC6UCRRRWPF4CBHX62FUAU3ZW3ZBZAVCNFSM6AAAAABOCCKWR6VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDGNJTGIYTOMZSGM> . You are receiving this because you were assigned.Message ID: ***@***.***>

[rmcdermo]

We'll work with you to get it in the FDS verification suite. If something is broken in FDS and this is the only case that demonstrates it, we need it in firebot.