[eSKa]

Hi,

I´ve got a big problem. I´m working with TurboGrid and CFD Simlution in the Workbench.

My Problem is: my fliud is very turbulent and the solution after x Iterations is not really converting.

My idea: take the arithmetic average of the last (e.g.) 50 Iteration to have a value to work with.

how I tried it: CFX\SETUP (pre):
-I created a Variable "VARpsi".
-I created a monitor point "MPpsi" of my variable "psi" in SOLVER\OUTPUT CONTROL\MONITOR.
-In this Monitor Point it shows me the Monitor Statictics of a "Moving Interval" about 50 "Iterations". The monitor Point works without Problems.
-I created an expression "avepsi" with the Definition : probe(Expression Value.Arithmetic Average) @MPpsi
-In the Geometry "R1" (where I want to have my average Value of the last 50 Iterations) I add to my Varibale "VARpsi" the Expression "avepsi"

CFX\RESULTS (post):
-Now I need the Output Paramameter: I created an expression "averagePsi" with the Definition: VARpsi @R1. R1 is here the Geometry where I want to have my value.


-In the next step I set the expression "averagePsi" as Output Parameter in the Workbench. after the Simulation the Parameter exists but without a value.


Do someone have some thoughts about this?
I´m thankfull for every help!


with regards
Sebastian

[urosgrivc]

average of the last 50 Iterations...

If you want moving average MA50
of any expression or variable you can set it up in CFX-solver manager in solution monitors so you can monitor it while the computation is going on.

[eSKa]

Hi, thank you.


I found the problem now.

In the POST there was a problem. Ansys CFD couldt recognize the Variable VARPsi.


in the POST:
for the first: I defined a Variable "VARpsi".
in the Expression averagePsi: instead of "VARpsi @R1 I defined it as "ave(VARpsi)@R1.
To take the average is here no problem because VARpsi is an average value.

Now it works because of a little trick, nbut I dont know why

[LehmannCFD]

Hello,
I want to do exactly the same as you did.
Unfortunately, I do not understand how you set up everything.
Could you explain again a little bit better?

Thank you in advance

[eSKa]

Hi.

I completed my work 2 years ago. I have only this describtion. You have to follow every step. I think its written clearly. If u couldn t understand a step pls ask.

[LehmannCFD]

Thanks for your reply :-)
In my case I have an automated workflow for a parameter optimization. Since the pressure loss (dp from inlet to outlet) is pulsating I want to have the average pressure loss of the last 50 iterations.


Is this summary of the workflow correct?

CFX\SETUP (pre):
1.1) Create a Variable "VARpsi"
1.2) Create a monitor point "MPpsi" of the variable "psi"
1.3) Set for this Monitor Point the Monitor Statictics: "Moving Interval about 50 "Iterations".
1.4) Create the expression "avepsi" with the Definition: probe(Expression Value.Arithmetic Average) @MPpsi
1.5) In the Geometry "R1" (where I want to have my average Value of the last 50 Iterations) I add to the varibale "VARpsi" the expression "avepsi"

CFX\RESULTS (post):
2.1) Define a Variable "VARpsi".
2.2) Create an expression "averagePsi" with the Definition: ave(VARpsi)@R1
2.3) Set "averagePsi" as output parameter


What I do not understand is:
-Step 1.1): Which definition has this variable?
-How do you link in CFX-Pre an expression and the variable?
-What is your geometry R1. Is it the outlet plane?
-What do you mean with the step 1.5). Could you explain it better?
-Step 2.1) is also not clear. What is the definition of this variable? With which expression do you link this variable?

[LehmannCFD]

Is there any other help available to solve this issue?

[ghorrocks]

The description you quote does not look very helpful to me. I would ignore it. It is for a steady state run and yours is transient for a start.

It is quite simple to do a running average of the pressure drop. Set a monitor point, option=expression, expression value=(whatever, maybe areaAve(p)@inlet-areaAve(p)@outlet), and set monitor statistics=on, Time=(averaging time you want).

To make this variable accessible in workbench you find the variable in CFD-Post and set it as an output parameter.

[LehmannCFD]

Hi Glenn

Thanks for your fast reply.
I did it exactly as you described in CFX-Pre.

Unfortunately, I can not find this variable/expression in CFD-Post.

The Monitor Statistics appear in the CFX-Solver-Manager-Monitor: dp(Arithemtic Average).

But afterwards in CFD-Post I can not find this Monitor Point Statistics any more. How and where can I find this Monitor Point?