Question regarding noslip wall on EB

[Pandakii]

Hi，

I am trying to simulate the supersonic flow inside a cavity flame-holder using PeleC. The irregular lower wall is built by function initialize_EB2(). In my test case, I use the command 'pelec.eb_noslip = 1 ' in the input file to set the EB condition as noslip wall. However, the test result shows that there is no boundary layer on the EB. The EB condition seemingly is slip wall. I do not know why the command 'pelec.eb_noslip = 1 ' is useless. This is my input file code-inp.txt.

I would appreciate it if anyone could help me.
Thanks in advance.

[marchdf]

This is indeed strange and not what I would expect. Are you using your own InitEB.cpp? We have a bunch of test cases that should catch this kind of thing. Including: https://amrex-combustion.github.io/PeleC/ebverification/C10/README.html#eb-c10 (https://github.com/AMReX-Combustion/PeleC/tree/development/Exec/RegTests/EB-C10). Can you make sure there isn't anything different in the input files/code you are using?

[marchdf]

It should work for all transport models. I just tried the ChannelFlow test case (uses Simple and air). I modified it to not do velocity perturbations and threw an EB in there. It develops a gradient at the EB boundary so I think it's all fine there too...

[Pandakii]

Thanks for your reply. I run the ChannelFlow test case and it works fine.

[Pandakii]

Hi Marc,

I modified the left boundary as the velocity inlet in the ChannelFlow case and only one side wall was set as EB. I found that the density and temperature gradients were different on the EB and domain boundary. It is strange and I am puzzled by this difference.

[marchdf]

this is odd... but I did have a thought yesterday. Can you plot viscosity? you have to add that keyword to the list of output vars.

[Pandakii]

This is the viscosity contour. The EB has the lower viscosity.

[hsitaram]

I wonder if this is a plotting issue? is this done using visit? I didnt see anything obvious in our implementation as our viscous test cases work fine.

[hsitaram]

I also noticed that you have only 8 cells along the out of plane direction while setting lo and hi_bcs as walls. In this paper we had used periodic bcs in the out of plane direction. I am wondering if the out of plane under-resolution may be the issue. Would you be able to rerun with periodic bcs in the z direction?

[marchdf]

I just ran EB-C10 to make sure nothing broke without us noticing. I definitely see a gradient at the wall... Is the bottom of your cavity an EB wall or just the domain BC set to a wall? Are you seeing a gradient there (I can't tell from your picture)?

[Pandakii]

I also noticed that you have only 8 cells along the out of plane direction while setting lo and hi_bcs as walls. In this paper we had used periodic bcs in the out of plane direction. I am wondering if the out of plane under-resolution may be the issue. Would you be able to rerun with periodic bcs in the z direction?
Thanks your comment. Please forgive me for not emphasizing that my case is two-dimensional. Is the issue causd by the 2D EB? Is it necessary to test a 3D case to compare result?

[marchdf]

2D should work.. Here is C10 with 2D:

[Pandakii]

I just ran EB-C10 to make sure nothing broke without us noticing. I definitely see a gradient at the wall... Is the bottom of your cavity an EB wall or just the domain BC set to a wall? Are you seeing a gradient there (I can't tell from your picture)?

The cavity bottom wall is the domain BC set to a wall. I checked my result and the gradient could form on the bottom wall. The issue only occurs on the EB.