Brinkman Eqns troubles with 'kapx_br , can not evaluate expression'

That is a strange error, the variable "kap_br", refers to the permeability (kappa) in the Brinkman equations "br" physics mode. So a similar error could arise if the variable was trying to be evaluated either in equation, boundary coefficients, or in a postprocessing expression and the physics mode was not present. However, "kapx_br" should not really exist in any form, so that is indeed quite peculiar.

To reproduce the issue, could you attach a model or script file that results in the error. And clarify what you mean with "scaling up" (as in making the geometry larger, or increasing the value of some coefficients?).

MarkJordan wrote

Brinkman Eqns:
Any time I try something other than the porous media example, and even just scaling up that example, I get the following error:
  Can not evaluate expression 'kapx_br'.

Any thoughts or suggestions?

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NAML

Thank you for reporting the issue. This turned out to be a parsing error for pressure stabilization (necessary for linear P1-P1 flow problem discretizations). If you select the "(P2P1)" "FEM discretization" element type in the "Subdomain Settings" dialog box (which automatically turns off artificial pressure stabilization), this issue is avoided. P2P1 elements are more accurate but require more memory and takes a bit longer to solve for which maybe isn't an issue for smaller problems.

Alternatively, a fix has been released with FEATool v1.11.1 Build 19.11.316 which can be downloaded from the FEATool Multiphysics GitHub repository (which always contains the latest releases). Select "About FEATool..." from the "Help" menu to see which release and build you are currently using.

MarkJordan wrote

attached is a simple example of the error
I've not been able to reproduce the error when scaling up a working model,
so that was probably something else I was doing wrong (new to mult-physics
modeling).
Mark

On Sun, Nov 10, 2019 at 8:34 PM Precise Simulation [via FEATool
Multiphysics Forum] <[hidden email]> wrote:

> That is a strange error, the variable "kap_br", refers to the permeability
> (kappa) in the Brinkman equations "br" physics mode. So a similar error
> could arise if the variable was trying to be evaluated either in equation,
> boundary coefficients, or in a postprocessing expression and the physics
> mode was not present. However, "kapx_br" should not really exist in any
> form, so that is indeed quite peculiar.
>
> To reproduce the issue, could you attach a model or script file that
> results in the error. And clarify what you mean with "scaling up" (as in
> making the geometry larger, or increasing the value of some coefficients?).
>
>
> MarkJordan wrote
> Brinkman Eqns:
> Any time I try something other than the porous media example, and even
> just scaling up that example, I get the following error:
>   Can not evaluate expression 'kapx_br'.
>
> Any thoughts or suggestions?