Account for variation in cell volume face area when setting up primitives and magnetic field values of ghost cells

[omerbr]

Hello, I am trying to implement transmissive boundary conditions on the axis of a cylindrical grid.
for this I am copying the primitive values from the innermost cells on one side of the axis to ghost cells on the other side of the axis. The problem is that the volume of the cells is different since there is a difference in the cylindrical radius of the cells.
The ghost cells of the inner radial boundary have a smaller cylindrical radius and a smaller volume than their counterparts cells in the computational domain. My question, do I need to account for the volume and face area differences when setting up the density, pressure and magnetic field values at the ghost cells, or is this difference is taken care of internally by the code through the grid metric?

[felker]

To be clear, are you asking about the details of / looking to use ix1_bc, ox1_bc radial outflow boundary conditions? https://github.com/PrincetonUniversity/athena/wiki/Boundary-Conditions

[omerbr]

Hi, Basically I am trying to implement "polar" boundary conditions on the ix1 direction in cylindrical geometry. In principle the "polar" bc is set for a spherical grid on the x2 direction. Omer

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On Mon, Jan 13, 2025 at 6:04 AM Kyle Gerard Felker ***@***.***> wrote: To be clear, are you asking about the details of / looking to use ix1_bc, ox1_bc radial outflow boundary conditions? https://github.com/PrincetonUniversity/athena/wiki/Boundary-Conditions — Reply to this email directly, view it on GitHub <#644 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AD3AOFP4XPZ3TR5SJOYWTJD2KM3NPAVCNFSM6AAAAABVBEUEIKVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTCOBRGU4TCMA> . You are receiving this because you authored the thread.Message ID: ***@***.*** com>