[FLASH-USERS] Mass Diffusivity

[Maximus Allfree]

Hey FLASH Users,


I have been trying to run simulations of the Richtmyer-Meshkov Instability and exploring the impacts of changing the Prandtl and Schmidt numbers. I am running this on a Mac.

For this I need diffusion, conduction, and viscosity. I asked about this a week or two ago, and thanks to those who offered help and support.

For anyone interested or maybe experiencing the same issue, when I was using the unsplit diffusion option, my program ran into a SIGSEGV error (Segmentation fault). I spent a week or so trying to work through my code to find the error. In the end I just downgraded HDF5 and, without changing my code, FLASH now runs fine without the SIGSEGV error, and I am getting decent results. No clue what this means but thought I would share.

Anyway, I have been trying to establish the Prandtl and Schmidt numbers into FLASH, however I have some questions:

In unit 22.1, looking at conduction constants, the doc says there is an option for a constant coefficient of diffusion. Would this be alpha, the thermal diffusivity constant, or is this k, the thermal conductivity constant?

Also, I need the mass diffusivity constant, D, to find the Schmidt number. Section 22.6 (mass diffusivity) is empty and says the unit provides only non-operational functionality. Is there any way I can specify the mass diffusivity with Hydro/Unsplit, or should I just try and calculate this myself from other parameters?

Thanks for reading!


Kind regards,
Max

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