Question about multiple boundary at top surface layers

[Bisesh Joshi]

Hi all,

I'm thinking of imposing two boundaries on the top (a) Neumann flux for recharge and (b) Dirichlet boundary for the sed-air interface to equilibrate with atmospheric pressure.

I'm wondering if this is a good approach or if it replaces the previous boundary condition when another boundary condition is applied to the same face.

Please let me know if you have any idea/suggestions regarding this.

Thank you.

Best regards,

Bisesh

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Bisesh Joshi

PhD student

Water Science and Policy

Graduate College

University of Delaware

901-297-6761

[Hammond, Glenn E]

Bisesh,

You may apply as many boundary conditions to a face as you desire. They are applied through superposition (i.e., they do not replace previous conditions).

To provide further direction, which flow mode are you using?

Glenn

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[Bisesh Joshi]

Hi Glenn,

Thank you so much for your quick reply.

I'm using Richard's mode.

Best regards,

Bisesh

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[Hammond, Glenn E]

Assuming that your application of a Dirichlet BC is to release recharge that cannot infiltrate, I would apply a SEEPAGE BC in addition to the recharge (for RICHARDS and TH). Water cannot enter the domain through the seepage BC unless the boundary pressure is >= 101325, but it can be released, and the gradient is calculated against 101325 [i.e., (Pcell - Patm)/distance].

For GENERAL mode, you can apply a separate Dirichlet BC that assigned a gas pressure (101325), relative humidity and temperature.

Glenn

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[Bisesh Joshi]

Thanks for your invaluable suggestion, Glenn. I will use seepage BC.

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