expert parameters : pressure value option = 3
 

Hello,

I need to set the static pressure by modifying the pressure value to 3 in the expert parameters section (Ansys CFX).

Can anyone help me with this PLEASE?

How can i apply this modification without any errors?

Thank you

In my 20 years of experience in CFX, I have never used this.
So I wonder, what do you need it for and what kind of error do you get?

Thank you Gert-Jan for your attention to my question.

In fact I work on the modeling of turbulence and interfacial transfer in two-phase flows with bubbles / drops in pipe. In the simulation protocol, when only the mean drag force is taken into account, one should expect an accumulation of the dispersed phase near the wall where the pressure decreases and the turbulence increases.

Except that as far as I understood, Ansys takes into account a modified pressure: the sum of the static pressure and a fluctuating term.

This alters the physics: the transverse pressure profile becomes constant, and the importance of turbulence in the parietal region becomes less, which gives another very different dispersed phase distribution result.

So I have to run the simulations with only the static pressure, to continue the simulations in a proper way for my case.

Are you trying to include the so-called Wall Lubrucation Force?

yes of course, i ill include it afterward, but to analyze the effect of each interfacial force i started with the mean drag force.

Moreover (always with only drag force), for the transverse profile of the relative longitudinal velocity I obtained as a result an acceleration near the wall in liquid-liquid flow, I would like to check if it is normal or not from a physical point of view.

is there anyone who can help me and explain to me the procedure to follow?

I cannot see any expert parameter named "pressure value option" in the documentation. What expert parameter are you thinking of using?

here capture photo from ansys theory solver on my question

OK, so it is just an expert parameter. Then if you want to use it you just set the expert parameter as the documentation says. So what is your question? Are you having problems setting the expert parameter? Or is it causing problems in the simulation results? (If so, what problems?)

my problem is that in the expert parameters section I can't find this option for the pressure.

I've gone through this whole section ... i didn't find it

Yes, this option does not appear to be in the standard list. You are going to need to use CCL to activate this option. If you are not familiar with CCL: Add any expert parameter in the GUI. Then on the object tree you should see the expert parameter option. Right click on the expert parameter tree object and select "Edit in Command Editor". This will show a text editor where you can edit the expert parameter to show "pressure value option = 3".

When you run the simulation the top of the output file lists the CCL for the run. Check that the expert parameter you want is in there as a final check that it worked.

okey i've done that, i had an attention message from cfx

In Analysis 'Flow Analysis 1': One or more expert parameters have been enabled. Note that expert parameters are intended for use only by customers who are experienced in the use of CFX, or who have been instructed to use them by ANSYS Customer Support. Use of the parameters is not fully supported, and may have unexpected or unintended consequences both for the quality of results and the performance of the CFX-Solver.

i run the simulation anyway?

You should take note of the warning - anything can happen when you adjust them and you are on your own. But if you want to see the effect of the parameter you discuss then continue and see if the simulation still runs and the results change.

Okey i will focus on that, thank you for your time :)

So there was no error, for which I asked. The real problem was that you didn't know how to implement an expert parameter that is not in the default list....?

I didn't mention that there was an error, just I reported what ansys specified in its documentation. My problem was how to change pressure value option = 1, 2 or 3 in CFX, since I couldn't find this option in the expert settings section.

In your first query you ask ".... how to apply this modification without errors".
This suggest you managed already, but it gave you errors.

Nevertheless, it is good that you got a solution through Glenn and are able to proceed.

sorry for the confusion, and thank you very much for any interaction