[BUAA LSM]

How do we initialize the domain? I have a cylindrical domain with oil and water. I want to initialize the outer ring of the field with water and the inner ring with oil. There is a patch option in Fluent that we can use to select a portion of the field and then initialize it. Is there a similar feature in CFX? thank you

[Gert-Jan]

If you have two domains then you can initialize per domain. However, two domains require two different mesh volumes which will be connected through an interface. If you study mixing oil and water, then it is better to not have an interface.
The option that remains is to write a CEL-expression which captures your initial distirbution with a step-function using the radius of the cilinder. Something like:

Radius = sqrt(x^2+y^2)
mf_ini = step(Radius/1[m]-0.15)

Your mf_ini will be 0 where radius is between 0 and 0.15. mf_ini will be 1 above 0.15.
The division by 1[m] is to make input for the step function dimensionless.
Using this mf_ini can be used to initialise your mass fractions.

When defining the expressions, there is a tab allowing you to plot the expressions. This helps to understand what you are defining.

[BUAA LSM]

Thank you very much for your help. I understand.