[jtipton2]

When creating expressions in CFX-Post, is it possible to force a hybrid calculation?

This question stems from my desire to calculate an average Nusselt number on the top surface of the outlet of a rectangular channel. To obtain the average heat flux I am using the following expression:

lengthAve(Wall Heat Flux)@TopLineOut

Here's the problem...

• If I open a result in CFX-Post and double click on my expression, I get a very large number (1.#INF [W m^-2]).
• If I next go to the calculator and calculate "lengthAve(Wall Heat Flux)@TopLineOut" I first get the result "Undefined".
• By pressing the "Hybrid" button, a reasonable value is then displayed.
• Finally, if I then go back to the expressions tab and click on my custom expression, the reasonable value is displayed and any other custom expressions that use a hybrid variable suddenly display reasonable numbers also.

Does anyone have an idea what is happening? This is very annoying and keeps me from using the Workbench parameter study feature.

[ghorrocks]

Hybrid/conservative value thing does not apply to surface integrals on boundary faces, but you are trying to do a line integral I assume on a boundary face. What I would consider doing is to replace your line integral with a surface integral where the surface you are integrating over is thin, so it is just about a line anyway. Then you evaluate the area integral and that should work fine.

[topsedar]

in CFX post go to:
Calculations ==> Function Calculator
then set your request. For example lengthAve(Wall Heat Flux)@TopLineOut

then at the bottom of Function Calculator tab, Press Hybrid button.
after this CFD Post automatically uses Hybrid Values For your Expression