Questions regarding boundary conditions and source terms

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1

Hello everybody, I have 2 questions if somebody could give some inputs.

  1. What is the (functional) difference between source term and Neumann pressure boundary condition?
    e.g. in the context of material/fluid inflow at a point - if we want to simulate fluid injection (or production) into the reservoir, and represent the injection place as a point, will the results be the same if we define the flow as a source term or as a Neumann pressure boundary condition (in that point)?

  2. Regarding temperature source terms - if we have a wellbore (represented as a 1D line mesh) in the domain, and want to dynamically simulate heat exchange between the reservoir and the wellbore (through python script).. Can we just calculate heat exchange values and define them as temperature source terms along the nodes of the wellbore 1D mesh, or do we need to also take into account the volume of cells connected to the node?

Thank you and best regards

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2

Hi marosaro,

  1. A volumetric source term and a Neumann BC behave identically in OGS: The integrand will be integrated over the provided geometry and added to the rhs of the global equation system. However, you can define a Nodal source term if you want to simulate injection at a single point.

  2. I’m not entirely sure what you mean. If you use a Python BC or Python source term on the 1D line mesh, there the fluxes you compute in the Python script will be integrated over the 1D line elements by OGS, i.e., in that sense you don’t have to worry about the volume of the adjacent (3D) cells.

Best regards,
Christoph