Modelling Turbulent Wall Functions
I'm doing a multiphase flow simulation and I have to model the wall roughness by using "turbulent wall functions". The CFX Theory Guide have an expression for this, but the big problem is in one of the variables.
The turbulent wall function uses the variable u* (I think that's the friction velocity or shear velocity). This variable is available for me in the Solver, but when I run the case, in the Post this variable does not appear (CFX says that it not exist). I'm needing this variable to calculate the film thickness and other variables of my case.
So, I would like to ask you how can I put this variable in my expressions. Is there any syntax? Remember that's a multiphase flow case.
I attached my CCL file, so you can look. The u* is in the "Uaster" expression, and that's the origin of all my problem here. The "wall turbulent function" is in the "WTFC" expression.
Thanks for your help.
Your function looks OK for a single phase flow. I suspect you need to get ustar for the phase you are interested in, not sure how to do that off the top of my head.
Does the ustar function work for a single phase flow?
Thanks for your answer ghorrocks.
I tried to run the case as single phase. Same problem on the ustar function. I'll try to run in other computer, and see if the same problem occur.
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