Isotropic Difusivity

Nishant_Sharma · June 10, 2018, 09:55

Hi all,

I have a small doubt, weather the fluent take the user defined diffusivity defined through UDF as isotropic by default or we have to specify it manually.

Thank you

obscureed · June 11, 2018, 12:25

Hi Nishant_Sharma,

I think it will become clearer when you try it. The answer might depend on whether you are talking about diffusivity of species or User-Defined Scalars (UDS), but in general isotropic is the default. For species, anisotropic diffusion can only occur in a porous zone, for some reason, and I'm not sure what UDF hooks exist there. For UDS, a different UDF type is required for anisotropic.

By the way, the numerics of anisotropic diffusion/conduction (for example, sensitivity to mesh quality) are significantly more troublesome than isotropic, so you should stick with isotropic if you possibly can.

Good luck!
Ed

Nishant_Sharma · June 14, 2018, 02:27

Thanks obscureed for your reply

, it was really helpfull.

June 10, 2018, 09:55	Isotropic Difusivity	#1
Nishant_Sharma Member Anomymous Join Date: May 2018 Posts: 31 Rep Power: 8	Hi all, I have a small doubt, weather the fluent take the user defined diffusivity defined through UDF as isotropic by default or we have to specify it manually. Thank you

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June 11, 2018, 12:25		#2
obscureed Senior Member Join Date: Sep 2017 Posts: 246 Rep Power: 12	Hi Nishant_Sharma, I think it will become clearer when you try it. The answer might depend on whether you are talking about diffusivity of species or User-Defined Scalars (UDS), but in general isotropic is the default. For species, anisotropic diffusion can only occur in a porous zone, for some reason, and I'm not sure what UDF hooks exist there. For UDS, a different UDF type is required for anisotropic. By the way, the numerics of anisotropic diffusion/conduction (for example, sensitivity to mesh quality) are significantly more troublesome than isotropic, so you should stick with isotropic if you possibly can. Good luck! Ed

June 14, 2018, 02:27		#3
Nishant_Sharma Member Anomymous Join Date: May 2018 Posts: 31 Rep Power: 8	Thanks obscureed for your reply , it was really helpfull.