Scalar transport problem in Fluent?
 

Hey fellow Fluent users,

I have a question regarding the scalar transport equations. To illustrate this take a simple closed geometry (i.e. lid-driven cavity flow). Solve for the velocity field in the domain. Then activate UDS and patch two different regions with different scalar values. Check the average value for the scalar then solve for scalar transport and check the average value again.

We can note that the average value is different before and after transport of the scalar. In my head the average value should be constant as long as we do not have any sources/sinks or open boundaries.

The scalar average value changes more rapidly for a few iterations and then it reaches a steady value. For me the error is large enough to cause the results to be useless.

Can anyone confirm this behavior?