Discussion Forum

Hi

I'm not sure I fully catch you, but lets say you have 2 materials (defined in the material nodes, and assigned one to each domain) then in the formulas you access these i.e. solid.rho which is mapped automatically to mat1.def.rho and respectively mat2.def.rho for domain 2 (asuming mat1 is on domain 1 ...)

by using the physics (i.e. solid) generic name for a material property i.e. solid.rho you leave to COMSOL to sort out the mapping how to extract the value. Note that solid.rho is in fact a field solid.rho(x,y,z,t) and the density might not be constant over a domain

There are many of these implicit fields with the COMOSL notation, in the biginning I found it confusing, but once you catch it you get used to it ;)

Note that mat1.def.rho is specifying the domain, in some sens and it you address your rho like that be sure it applies only to the domain mapped by "mat1"

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Good luck
Ivar

Ok, I'll try to make a bit clearer. I have a geometry with 2 domains, both use the same material, but they have different physical properties (one is powder, on is dense) which are computed via different functions for the physical values. An example: The density rho is rho(T) for domain one, but (1-abc)*rho(T) for domain 2. abc is stored a local parameter under the material node in the def group, so the formula I entered for rho in domain 2 looks like (1-mat1.def.abc)*mat1.def.rho(T). Instead of mat1.def. is there a possibility to tell Comsol to use the specific parameter abc of the material that is assigned to the domain, maybe something like assignedmaterial.def? I could use two different materials, but I'd prefer to use just one material definition.

It would just be convinient for the later user of the model, if he could just assign a different material to the geometry and if he had not to delete the first material in the first place and then add the new material.

Hi

I'm not next to my COMSOL WS so I cannot check, but, if I read you correctly) cannt you define the same material for both domains then in the first physics node (for solid it would be linear material node) you select
Density rho user defined and try something like: rho*(1+abc*(dom==1)) or use an "if()" operator

or you define 2 lienar material nodes, andwhere you need to use the abc variable you replace the material value by your User defined formula

Pls check carefully e.g. by loading the initial values (solver Dependent variables node => Compute to selected) and by plotting "rho" over both domains

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Good luck
Ivar

Hm, that's an interesting idea. I'll give it a try.

Thank a lot :-)