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Old   January 29, 2009, 01:28
Default Reg. UDF
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Hi , I am Nabil pursuing M.Tech chemical Engg. program in Anna University Chennai. I want to write an UDF for my project work on fluidized beds.

How can i get the value of gradient of a scalar variable?? Is there any inbuilt macros to get the gradient value of voidage (i.e., volume fraction of phase-1)??

Gradient in the sense 'del(phi)'
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Old   January 30, 2009, 08:30
Default Re: Reg. UDF
KJ Larsen
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Hello Nabil

There is a macro which gives you the vector of the gradient for volume fraction of a species in space.

C_YI_G(c,t,i) is the gradient vector of the ith species.

= [d/dx ; d/dy ; d/dz](phi)

The information is available in the UDF Manual (3.2.3)

Hope that helps. Kris
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Old   January 31, 2009, 12:12
Default Re: Reg. UDF
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Hello Kris,

Thank You for your reply..

I have two doubts sir

1. The macro C_YI_G(c,t,i) gives the species mass fraction gradient vector. But i need volume fraction gradient vector.

2. The macro C_VOF(c,t) gives volume fraction for the phase corresponding to phase thread t. Whether this macro is for VOF multiphase model alone or we can use for Eulerian model also???. If so is there anything like C_VOF_G(c,t,i) so that i can apply to get volume fraction gradient vector.

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