Question onf Uniform Temperature Environment

[sprankleray]

I am curious about the uniform temperature environment example used in the Verification file radiation_2.in, downloaded from Github. The text in the V&V Guide, Section 3.4.2, states that this case models a furnace with a uniform temperature of 500°C. However, the input file, using the diagnostic parameter “DIAG” as shown below, uses F = 226.85. The Table in Section B.12 of the User’s Guide states the “F” parameter is in units of °C. While 226.85°C is equivalent to 500K, one might expect the room temperature to end up at 226.85°C (500K); but it results in room temperatures of 500°C. How does this work?

Say I want a room temperature of 500°C
So, I input an “F” value of 226.85°C (500K) and
The result is a room temperature of 500°C

It seems like the value selected for “F” should be the centigrade equivalent of the desired centigrade room temperature in Kelvin. For example, if I want the room environment at say 123°C, I set F = -150.15 or the centigrade equivalent of 123K.

This does seem to work but it doesn't seem to make sense. Can you please explain.

Note the "&MISC" command sets the room boundaries to be adiabatic. While this doesn't really pertain to the question above, it certainly pertains to establishing a uniform temperature environment.

Thanks in advance for your help.
Ray

Diagnostic parameter in radiation_2.in
&MISC ADIABATIC = .TRUE. /
&DIAG T = 0, 10000
F = 226.85, 226.85 /

[mcgratta]

This might be a typo. I'll take a look.

[rpeacoc]

I think Andy created this V&V case. You might have him look to make sure case is correct

[mcgratta]

It seems that F on the DIAG line is read and immediately has 273.15 added to it. Then, in the radiation routine, it has another 273.15 added to it. Two wrongs are making a right here. The furnace temperature is 500 C, but the 226.85 was input just to right the wrong. I'll see if I can fix this. In the meantime, the case is working properly except for the fact that the inputs have been hacked to work.

[rpeacoc]

Is the second time at line 1176 of Solve.f90?

[mcgratta]

Yes, see my PR that I just assigned to you and Paul. If you agree with my diagnosis, accept the PR.

[mcgratta]

Question -- is the T and F on the DIAG line used solely for setting a furnace temperature?

[rpeacoc]

I think it's an easy fix. I'll try and V&V it.

Yes, T and F in the &DIAG is only for setting gas temperature. It was meant just and the verification tests that Andy put together.

[mcgratta]

Another question while I'm on the subject. What does "Selection List" mean in this table

[rpeacoc]

It means that inputs can only be from specific inputs, for example "ON" or "OFF." Details of allowable inputs are in the footnotes.

[mcgratta]

I don't understand. Wouldn't most of these be logical parameters that are T or F? How is ON or OFF conveyed in the input file?

[rpeacoc]

True, but a selection list could include more than two possible inputs.

[preneke]

ON and OFF are just meant to make the input files more readable and converting them to TRUE and FALSE is a small amount of code. From: Kevin McGrattan ***@***.***> Sent: Wednesday, September 3, 2025 2:01 PM To: firemodels/cfast ***@***.***> Cc: Subscribed ***@***.***> Subject: [EXTERNAL] Re: [firemodels/cfast] Question onf Uniform Temperature Environment (Discussion #2208) I don't understand. Wouldn't most of these be logical parameters that are T or F? How is ON or OFF conveyed in the input file? - Reply to this email directly, view it on GitHub<#2208 (reply in thread)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ADDV4MD6R65OPTZNKHYQHED3Q4UHBAVCNFSM6AAAAACFOUMYMSVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTIMRZHA4TSNQ>. You are receiving this because you are subscribed to this thread.Message ID: ***@***.******@***.***>>

[mcgratta]

Does one write

&DIAG FIRE_SUB_MODEL='ON'

[preneke]

Yep. It is in input.namelist.f90 in subroutine read_diag. FIRE_SUB_MODEL defaults to 'ON' so you only need it if you are turning off the sub model. All the models default to 'ON' but some of the other stuff have different defaults. &DIAG is not really meant for users. We don't want to hide it from them but in general they don't really need to use it. From: Kevin McGrattan ***@***.***> Sent: Wednesday, September 3, 2025 2:12 PM To: firemodels/cfast ***@***.***> Cc: Reneke, Paul A. (Fed) ***@***.***>; Comment ***@***.***> Subject: [EXTERNAL] Re: [firemodels/cfast] Question onf Uniform Temperature Environment (Discussion #2208) Does one write &DIAG FIRE_SUB_MODEL='ON' - Reply to this email directly, view it on GitHub<#2208 (reply in thread)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ADDV4MAYMHD2OIBFBIWAIDD3Q4VOLAVCNFSM6AAAAACFOUMYMSVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTIMRZHEYDOMA>. You are receiving this because you commented.Message ID: ***@***.******@***.***>>

[rpeacoc]

This error should be fixed now. Nightly release tomorrow morning should reflect the changes. Commit 27b21bb includes changes to code and verification input file. V&V shows no change in output.

[sprankleray]

Thank you all for helping out.