Regarding EB boundary conditions

[RSuryaNarayan]

Hello everyone, I have a question on the boundary conditions available currently for treating EB surfaces.
I see that there is an input:

pelec.eb_isothermal =1
pelec.eb_boundary_T = 1000 # this is the EB surface temperature

What is the default thermal treatment for the EB surface (i.e. if none of the above are provided?).
Is it adiabatic?

[hsitaram]

Yes, it's an adiabatic wall by default.

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On Sun, Jul 18, 2021, 12:34 RSuryaNarayan ***@***.***> wrote: Hello everyone, I have a question on the boundary conditions available currently for treating EB surfaces. I see that there is an input: pelec.eb_isothermal =1 pelec.eb_boundary_T = 1000 # this is the EB surface temperature What is the default thermal treatment for the EB surface (i.e. if none of the above are provided?). Is it adiabatic? — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#313>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABYOQM2YOKVNBSC4A2XI47LTYMNDZANCNFSM5ASMJRNA> .

[marchdf]

Hi all, I created PR #319 to the docs for clarifying that GC-NSCBC has not yet been ported to C++ from Fortran. Thanks for bringing it to our attention.

[RSuryaNarayan]

@marchdf thanks, so currently we have only first order extrapolation as a way to accomplish a perfectly non-reflecting BC?

[marchdf]

So you can try first order extrapolation and hope to get lucky. If that doesn't work, you can try to specify the ghost cell values in a way that reduces reflections. A good example of that is what I do in EB-C10: https://github.com/AMReX-Combustion/PeleC/blob/development/Exec/RegTests/EB-C10/prob.H#L91 which attempts to follow Blazek's subsonic outflow condition. I've had good luck with that but it's by no means full-proof or perfect.

[RSuryaNarayan]

Thanks! FOExtrap worked for the acoustic pulse in channel case (EB-C9). I also have cases where I need a part of the wall as a non-reflecting wall and partly as an inflow. I think Blazek's method should work as a replacement for FOExtrap here.

[marchdf]

I guess it's not too surprising that it would work for that case. It's a weak acoustic pulse. Nothing crazy going on. We've seen FOExtrap fail for things that have fluctuating velocities (e.g. turbulence...)