Learning Forum

[Raiq33]

Hi,I'm currying out a simulation using nonpremixed combustion model. I want to add an additional term to the mixture fraction transport equation. According to the UDF manual, you can add an additional source term but the term I want to add is not a source term. nCan you please guide to the right direction to add the new term in the mixture fraction transport equation? n

[YasserSelima]

What is the issue of adding this term as a source? it will still be part of the equation.n

[Raiq33]

nTo be honest, I do not see any issue but why does the Fluent establisher provide that option for only the source term NOT the transient, convection or diffusion terms !?n

[YasserSelima]

It provides macros to define diffusivity and other parameters ... not just source n

[Raiq33]

yes, you're right but it provides these macros for UDS not for the governing equations.n

[DrAmine]

Because you can create your own models with a standard UDS framework.n

[Raiq33]

Does this mean it is not possible to add a new term to the governing equations without using DEFINE_SOURCE macro although this new term is not a source term? if yes, is it logical from a CFD perspective to add transient, convection or diffusion terms as a source term? n

[YasserSelima]

You can use define diffusivity to define heat diffusion ... Energy Equation .. and you can define properties like viscosity and density to change momentum diffusivity ... nAnd you can use define source for the UDS as well.nnMathematically, any hanging term or added term in the transport equation is a source ... even if it is not a physical source.n