CFX Post: Only shows last time step result
 

I have done a simulation for sinusoidal movement of a piston merged at a fluid.
When I look at CFX Post for Force Vs Displacement curve at chart view It only shows last time step result.

I have used here: Total Time=1 sec.
Time step =0.01 sec.

At output control >>Transient Result>>Standard and time interval 2

Any one can help me to solve this issue. Thanks in advance.

Time interval is an absolute value with a unit - I suspect [s] is default value. So for your total run of 1 s, you get no additional output.


You can easily check if transient output was written if you look into the simulation folder, there will be an additional folder with the run number appended, e.g. _001. If transient output was written, there will be files in .trn file format inside this folder. If there is nothing there, nothing was written and therefore nothing will be shown in CFD-Post.

You can either adjust the time interval to 0.02 [s] or switch to time step interval 2 for example.

Thanks AtoHM for your co-operation

I have tried for Total time 2 s and Time step 0.02 s Then nothing observed as --- .trn file.

But When I run simulation again for Total time 2 S and time step 0.01 s then I get a file named "104_full.trn". At time step selector shows 2 step. Also I get a curve like straight line. But the actual curve is not like a straight line.

CFD-Post can only display data you generate a transient results file for.

If you want to see plots of things versus time at full resolution the best way is to define it as a monitor point in CFX-Pre, rerun the simulation and then the full time history will be available as a monitor point in Solver Manager. You don't use CFD-Post to get the full time history.

Dear Glenn

I have used below equation for displacement:

Displacement= 0.0425[m]*cos(1.33*t/1 [s])

For calculating Force I have used below expression at CFD post:

Force= force_y()@piston+force_y()@pistonwall

At Pre, Total Time=1 S and Time step=0.01 s

I want more than 90 set data for generating my curve. How can I input monitor for my required data set?

I have attached here my geometry pic for your better understanding about my work.

Thanks in advance for your best co-operation.


Rubel

As I said previously, add a monitor point to your output tab in CFX-Pre. Then re-run the simulation. In solver manager you will have a chart display which shows the output of the monitor point for all time steps.

Dear Glenn,

Actually I don't get how can I add monitor point for required data. Could you please tell me elaborately what will be the next process after selecting monitor point.




Rubel

Change the option from "Cartesian Coordinates" to "CEL Expression", then put your displacement or force expression in.

Dear Glenn,

I have written Force expression "force_y()@piston+force_y()@pistonwall" at CFX-Post as a new expression.

How can I put it at monitor?

Is there another way to collect force data or how can I write expression for damping force?


By the way, I have added "Displacement= 0.0425[m]*cos(1.33*t/1 [s]) at monitor point 2

and Force= force_y()@piston+force_y()@pistonwall at monitor point 1

But still I don't get any result.



With Regards
Rubel

You can't put it in CFD-Post. It does not have the data.

You have to put it in CFX-Pre as a monitor point and rerun the simulation. If you don't know how to do monitor points have a look at the CFX tutorials.

You then access the monitor point data through solver manager, not through CFD-Post.

Thanks Glenn Finally it works
:)