How to implement Neumann boundary conditions in Xcompact3D? Any existing code samples?

[tambeyash]

Hi all,
I’m trying to implement Neumann (zero-gradient / prescribed normal derivative) boundary conditions in Xcompact3D. Has anyone implemented Neumann BCs in this codebase before? If yes, could you please point me to the files/branches or share a code snippet showing how you applied the Neumann condition (for velocity or scalar fields)?

What I’m after:

• Where to modify boundary condition routines (which files/modules)?
• How to apply Neumann BCs consistently in the solver?
• Any pitfalls or problems you face after implementing those?

Thanks

[mathrack]

Hello,

You can impose symmetry boundary conditions on the velocity using the input file : set nclx1 and nclxn to one to impose symmetry in the direction x. Zero is used for periodicity. Two in case of walls.

You can impose similar conditions on scalars using nclxS1 and nclxSn. In case of symmetry, you can define scalars with odd / even symmetry. Check for the variable sc_even in the source code.

Cheers,
Mathrack

[tambeyash]

Thanks a lot for your response.
I am trying to set up the laminar wall-jet case. I’m quite new to CFD, and fluid dynamics in general, so I’ll need to study your solution more carefully to fully understand it. But it definitely gives me a direction to work in. If I run into related issues while implementing it, I’ll follow up here.

Thanks and Regards,
Yash