Combination of Symmetry and No-slip wall BCs

[SRkumar97]

Hi,
I want run an external boundary layer case over a flat domain. I want to setup the case in the exact same manner as this schematic below, but for compressible flow. Image courtesy - NASA LaRC

Now, at the base of the 3D domain, I will need to use Symmetry for an initial distance, followed by No-slip wall from the region of interest, I wish to know how to combine and set this case up. All I know is that the "Hard" BC type has to be employed here. However, what is the best way to inform the code to smartly use Symmetry and No-Slip wall BCs, in the respective if{}-else{} statements of these regions, in subroutine bcnormal() of prob.H? I believe I'd mess up many things if I chose to manually specify every flow field variable matrix using s_int and s_ext, especially in the viscous no-slip wall region.
Thanks a ton in advance!

[baperry2]

This is actually pretty easy to accomplish. s_ext that gets passed to bcnormal comes prepopulated with values for a no-slip wall. to specify a symmetry condition (equivalent to a slip wall), all you need to do is change the sign of the tangential components of velocity. See the example in the MassCons case, which shows how to define both slip and no-slip walls in bcnormal:

PeleC/Exec/RegTests/MassCons/prob.H

Line 71 in 4ba05a8

if (prob_parm.wall_type[idir] == 1) {

Documentation: https://amrex-combustion.github.io/PeleC/BoundaryConditions.html#boundary-conditions

[baperry2]

Those scripts run a few cases and then process data from them to verify numerical convergence for isothermal walls and mass conservation, respectively. You do not need to worry about them if you don't want to.

[SRkumar97]

Ohh, ok. Thanks for the clarification.

[SRkumar97]

In the input files of this case, there is this parameter prob.wall_type which I have never encountered before, nor do I see any mention of it in the official PeleC documentation site. Does this correspond/replicate the same kind of wall BC as pelec.do_isothermal_walls?

[baperry2]

Any input prefixed with prob is problem specific and defined in that problems case files. In this case, that input parameter is documented for the README for the case, and you can also look in the prob.{H,cpp} and prob_parm.H files for how it iis defined/used.

[SRkumar97]

Thanks, I didn't understand this clearly before.