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gradient source term UDF

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Old   July 9, 2009, 06:37
Default gradient source term UDF
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hi everyone,

I have a user defined scalar for a variable Q, and a user defined scalar for a variable V. In the scalar equation for Q, a source term appears as follows:

(Dq/dx)*(DV/dx)*constants (1)

where the variable Q appears as a source term for the user defined scalar equation for V as (Q/constant). Everything works beautifully when I turn this source term (eq 1) OFF.

The way I implemented this source term (equation 1) is within a DEFINE_SOURCE function as

where dS[eqn]=0

and the solution diverges. I am pretty sure this is because of a checkerboarding effect as with pressure-velocity coupling. I therefore probably need to manually discretise the source term in the FLUENT UDF can I access north,south,west and east nodal positions so that I can do this in 2D?? and later in 3D? is this even possible in fluent?? This has been troubling me for quite some time now...any help is appreciated.

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