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Simple Question: Transport of Diluted Species

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Hello,

"Transport of Diluted Species" >> "Convection and Diffusion" >> Diffusion >> Bulk Material

What is "Bulk Material"? Choosing "None" or Material I used makes any difference?

Thanks.




1 Reply Last Post 22.01.2012, 12:10 GMT-5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 22.01.2012, 12:10 GMT-5
Hi

from my understanding its the static material, i.e. if you have water diffusing in some sand, the bulk is the sand, and the diffusing material is the water => bulk -> sand

But then if the diffusivity Dc is not defined in the bulk material (i.e."sand") then the same user defined diffusivity Dc is used so it seems that there are no changes, however, if the diffusivity is defined in the bulk material selected, then you can switch to the "User defined property group" that I understand is the material variable Dc

Most other fields operate the other way: by default its the material properties that apply, and you can manually override, here its the manual that is the default and you must override specifically 2x to get the material properties used

--
Good luck
Ivar
Hi from my understanding its the static material, i.e. if you have water diffusing in some sand, the bulk is the sand, and the diffusing material is the water => bulk -> sand But then if the diffusivity Dc is not defined in the bulk material (i.e."sand") then the same user defined diffusivity Dc is used so it seems that there are no changes, however, if the diffusivity is defined in the bulk material selected, then you can switch to the "User defined property group" that I understand is the material variable Dc Most other fields operate the other way: by default its the material properties that apply, and you can manually override, here its the manual that is the default and you must override specifically 2x to get the material properties used -- Good luck Ivar

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