Take strain_free_density as initial value for density calculation

[tophmatthews]

Creates new MaterialPropertyName strain_free_density that will replace the now deprecated density param. This enables the use of a material property for density independent of strains (say for example, dependent on chemistry), which can be changed throughout a simulation. Added test for Density in modules/misc/test/tests as well since Density is in the misc module, but is only tested in combined (almost seems like density should be in solid_mechanics but whatevs).

ping maybe @bwspenc and @dschwen ?

Closes #29556

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	32662f	#29773 443539
	Total	Total	+/-	New
Rate	60.92%	69.62%	+8.69%	91.67%
Hits	251	291	+40	11
Misses	161	127	-34	1

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• 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
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• solid_mechanics
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• stochastic_tools
• thermal_hydraulics
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[tophmatthews]

Ready for you to take a look @bwspenc thanks!

[bwspenc]

@tophmatthews I think it's in misc because it's used by the heat_transfer module as well as mechanics.

[bwspenc]

This looks good to me. My only comment is that to me, it seems like it would be more natural to name the property name and input parameter initial_density rather thanstrain_free_density. Since that's how you chose to name your member variable that points to the input parameter I think you might feel the same way.

[tophmatthews]

I think it's in misc because it's used by the heat_transfer module as well as mechanics.

Hm, I thought I removed a lot of "Density" at some point. Could just be a GenericConstantMaterial anyways. I'll look into this.

[bwspenc]

I guess it's up to the user to use whatever material model is most appropriate to define density, so they could use either this or GenericConstantMaterial.

[tophmatthews]

input parameter initial_density rather thanstrain_free_density.

Yeah good suggestion. The bare minimum need for Density is an initial density. The use case added here is for evolving density due to everything but strain (e.g., changing chemistry conditions that changes density). Since strain_free_density kinda captures both, while using initial_density implies it's only the original, I went with strain_free_density. Does that make sense?

[tophmatthews]

I guess it's up to the user to use whatever material model is most appropriate to define density, so they could use either this or GenericConstantMaterial.

Interestingly, there is an old comment in Density.C

// TODO: We should deprecate the !_is_coupled case and have the
  // user use a GenericConstantMaterial
  if (_is_coupled)

I didn't touch this at this time, but it does make a good point that unless you are using displacements, you don't need Density.C

[tophmatthews]

I dont see Density in any other module except Combined (except for misc added in this PR).

[tophmatthews]

it's in gui/tests and python/peacock. Not sure if those are pulling only misc and not solid_mechanics though.