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-   -   a problem about user define scalars(uds) (http://www.cfd-online.com/Forums/fluent/103699-problem-about-user-define-scalars-uds.html)

chenxizh June 24, 2012 04:32

a problem about user define scalars(uds)
 
Hi, all. Recently I want to use Fluent's user define scalars(uds) in a multiphase problem . I find that the uds in multiphase has the following formulation
http://hpce.iitm.ac.in/website/Manua...ug/img2694.gif

So I have a problem about the diffusion term. When I input the value "uds diffsivity" In "Create /Edit Material " should I multiply by the density and the voidage myself ? Or Fluent will auto multiply the voidage of the phase?
Can anybody help me? thanks.

akm June 27, 2012 07:40

As you can see in the uds equation, diffusivity \Gamma^{k}_{l} should be given to Fluent in the form ML^{-1}T^{-1} -- same units as dynamic viscosity (Pa.s).

Fluent takes care of multiplying by voidage itself.


Quote:

Originally Posted by chenxizh (Post 368016)
Hi, all. Recently I want to use Fluent's user define scalars(uds) in a multiphase problem . I find that the uds in multiphase has the following formulation
http://hpce.iitm.ac.in/website/Manua...ug/img2694.gif

So I have a problem about the diffusion term. When I input the value "uds diffsivity" In "Create /Edit Material " should I multiply by the density and the voidage myself ? Or Fluent will auto multiply the voidage of the phase?
Can anybody help me? thanks.


chenxizh June 29, 2012 08:44

Hi, So you mean that I should give the value "density multiply the diffusivity coefficention" and ignore the voidage thing, Did I get it? thanks.
Quote:

Originally Posted by akm (Post 368539)
As you can see in the uds equation, diffusivity \Gamma^{k}_{l} should be given to Fluent in the form ML^{-1}T^{-1} -- same units as dynamic viscosity (Pa.s).

Fluent takes care of multiplying by voidage itself.



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