[CaptainCombo]

I would like to add the terms shown in picture below to each components of the momentum equation. Is there a way to define d/dx, d/dy and d/dz by using UDF macros? Also, if I achieve to do that does Fluent discretize and solve these terms just as it does other derivaives in momentum equation?

[pakk]

You're not showing terms, but an operator... What should this operate on?

(or maybe a better question to avoid follow up questions: can you write your momentum equation?)

[CaptainCombo]

Originally Posted by pakk

You're not showing terms, but an operator... What should this operate on?

(or maybe a better question to avoid follow up questions: can you write your momentum equation?)

Actually I mean Mx d/dx, My d/dy and Mz d/dz as terms. There is nothing after derivatives (d/dx, d/dy, d/dz). Anyway here is the whole equation;

[pakk]

You say that there is nothing after the derivatives, but your equation shows that there is a vector B after the derivatives...

Is B the magnetic field? Fluent does not calculate the magnetic field (as far as I know), so you need to put in the magnetic field yourself. And taking the gradient of the magnetic field is an extra step that you have to do yourself also...