Let users use variables as coordinates to a function in an auxkernel

[GiudGiud]

I have a project where we have function data that is hardly convertible to another format (eg we would need to write an object that does what the function reading the csv does)
and an auxiliary variable that is spatial but not x y z (it s a distance to a wall). So it would fit great as a function argument conceptually. Unfortunately, ParsedFunction does not accept auxvariables.

So our two options (aside from this) would be:

• create a new matprop or auxkernel that includes the function work, and either includes the wall distance computation work or accept an aux variable. Keep this object in an app since it cant go in MOOSE
• create a new matprop or auxkernel that takes the function and the auxvariable as arguments and does this operation we have here but with dedicated names and only supports the 1 need we have. Also cant go in moose and it s just a less general version of this object

The concerns with having functions depend on variables:

• no automated dependency resolution that ensures the auxvariables are up to date when they are used in the function as arguments. Some of the functors (PPs) are not the best at this anyway
• blurs the lines between systems. Functions should be xyzt, AuxVariables kind of an output tool and material properties for having actual variable dependencies in terms that come in the equations
• loses derivatives. But that s the case with ALL auxkernels so that concern is not new

refs #26784

@youyeonc

[moosebuild]

Job Documentation on 95a9ed7 wanted to post the following:

View the site here

This comment will be updated on new commits.

[moosebuild]

Job Coverage on 95a9ed7 wanted to post the following:

Framework coverage

	a489a5	#27081 95a9ed
	Total	Total	+/-	New
Rate	85.12%	85.12%	+0.00%	92.86%
Hits	102933	102974	+41	39
Misses	18001	18002	+1	3

Diff coverage report

Full coverage report

Modules coverage

Coverage did not change

Full coverage reports

Reports

• framework
• chemical_reactions
• combined
• contact
• electromagnetics
• external_petsc_solver
• fluid_properties
• fsi
• functional_expansion_tools
• geochemistry
• heat_transfer
• level_set
• misc
• navier_stokes
• optimization
• peridynamics
• phase_field
• porous_flow
• ray_tracing
• rdg
• reactor
• richards
• scalar_transport
• solid_mechanics
• solid_properties
• stochastic_tools
• thermal_hydraulics
• xfem

This comment will be updated on new commits.

[dschwen]

That title is confusing. It sounds like you want to let users pass variable names as arguments to parameters of type FunctionName. What you are doing is providing an AuxKernel that evaluates a Function at xyzt coordinates determined through functors. Does not sound like "Abuse", so I vote for fixing that name.

[GiudGiud]

Fixed the pr title.
Thoughts for the name?

FunctionWithFunctorCoordinatesAux?
FunctorPositionFunctionAux?

[GiudGiud]

@dschwen thoughts on picking a new name?

[GiudGiud]

Now that you are back @dschwen thoughts for the name?

[dschwen]

CoupledVariableCoordinateFunctorAux?

[GiudGiud]

It s more of a FunctionAux since the Function is used for the evaluations
and the variables are not coordinates, I use functor for those

so maybe FunctorCoordinatesFunctionAux ?

[GiudGiud]

Failures are unrelated

[GiudGiud]

@lindsayad @dschwen

[lindsayad]

I actually very much like this PR

[GiudGiud]

Test failures unrelated.
thanks for the review!