[FLASH-USERS] [EXT] Re: question about radslab

[Hansen, Eddie]

Actually, I think I understand now…

With the way RadSlab works, you can think of RadTrans_mgdUFromT as the routine that sets the radiation energy densities per group just for the Dirichlet boundary (i.e., the radiation source). The analogous lines in RadTrans.F90 that set emission are just for the cells inside the domain. So, I’ve never tried it before, but you should be free to independently adjust the relationship between urad() and T inside RadTrans_mgdUFromT however you want. Does that make more sense and answer your questions?

--
Eddie Hansen
Applications Group Leader
Flash Center for Computational Science


From: flash-users <flash-users-bounces at flash.rochester.edu> on behalf of Hansen, Eddie <ehansen at pas.rochester.edu>
Date: Wednesday, January 8, 2025 at 7:37 PM
To: Youssef Abouhussien <abouhussieny at vcu.edu>
Cc: flash-users at flash.rochester.edu <flash-users at flash.rochester.edu>
Subject: Re: [FLASH-USERS] [EXT] Re: question about radslab
I’m not sure exactly what you’re trying to accomplish. Multi-group radiation transport is not independent of absorption or emission. Transport, absorption, and emission are all solved simultaneously per radiation energy group.

Changing urad_tot in that routine won’t actually do anything since that variable is not actually passed out of the subroutine. The important one is urad() which is the radiation energy density per group. If you want to change the relationship between energy density U and T, then that’s more complicated…

You would make changes in RadTrans_mgdUFromT to make the Dirichlet BC work the way you want it to, but you would also have to make corresponding changes in RadTrans.F90 to make the emission term consistent.

--
Eddie Hansen
Applications Group Leader
Flash Center for Computational Science


From: Youssef Abouhussien <abouhussieny at vcu.edu>
Date: Wednesday, January 8, 2025 at 7:10 PM
To: Hansen, Eddie <ehansen at pas.rochester.edu>
Cc: flash-users at flash.rochester.edu <flash-users at flash.rochester.edu>
Subject: [EXT] Re: [FLASH-USERS] question about radslab
Hi Eddie,

Thank you for your email. I still want the radiation transport (hence wavelengths of the photons) to be carried out at a specific temperature. If I modified "urad_tot = urad_tot + urad(g)" from  RadTrans_mgdUFromT.90 file and multiplied it by a constant to decrease the energy deposited to match the intensity i have in mind; would that work? Thanks.

Regards,
Youssef


------------------------------------------------------------------------------------------------------
Youssef Abouhussien
Research Assistant
Doctoral Student
Virginia Commonwealth University
Dept. of Mechanical and Nuclear Engineering


On Wed, Jan 8, 2025 at 6:58 PM Hansen, Eddie <ehansen at pas.rochester.edu<mailto:ehansen at pas.rochester.edu>> wrote:
Hi Youssef,

The BC for RadSlab is not spatially-varying; it is just a single radiation temperature along the entire Yl boundary (the “dirichlet” boundary). There are runtime parameters that control the value of that temperature and some time-dependence, which are used in Simulation_adjustEvolution.

If you have a specific intensity in mind, then you’d have to calculate what temperature that would be (e.g., I ~ T^4 for a blackbody).

--
Eddie Hansen
Applications Group Leader
Flash Center for Computational Science


From: flash-users <flash-users-bounces at flash.rochester.edu<mailto:flash-users-bounces at flash.rochester.edu>> on behalf of Youssef Abouhussien <abouhussieny at vcu.edu<mailto:abouhussieny at vcu.edu>>
Date: Saturday, January 4, 2025 at 4:31 PM
To: flash-users at flash.rochester.edu<mailto:flash-users at flash.rochester.edu> <flash-users at flash.rochester.edu<mailto:flash-users at flash.rochester.edu>>
Subject: [FLASH-USERS] question about radslab
Hi flash users,

In RadSlab example for X-rays ablation, how can you specify the intensity? usually for blackbody source it's specified by the radiation temperature (cant change that for radiation transport purposes) and distance from target (for a point source) .

Also i cant tell where the location of the source or shape (planar, point etc ) .

thanks.

Regards,
Youssef


------------------------------------------------------------------------------------------------------
Youssef Abouhussien
Research Assistant
Doctoral Student
Virginia Commonwealth University
Dept. of Mechanical and Nuclear Engineering
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