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drag coefficient dependence on time

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Old   January 23, 2013, 05:44
Default drag coefficient dependence on time
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Hay.
I''m modeling Transient laminar flow around cylinder. A question is how to get data where will be current time and drag coefficient.
For example Let the Reynolds number be 500.
And I'm doing these steps: Solutions->Monitors->create->Drag. Unfortunately in the text file I only get the last time step and drag coefficient, but I need all time steps and CD.
Also I'm traying Calculation activites->Solution animation->every time step->Monitor->create drag monitor.
That action also write only the last step.
Please help.
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Old   January 23, 2013, 08:54
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I think you should use UDF.
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Old   January 23, 2013, 11:08
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It's ridiculous, but I have two times done that I'm seeking to do, but now I can't understand where is a problem that I can't get previous results.
Anyone else have similar problem?
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Old   January 23, 2013, 11:40
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那你问你妹啊,傻逼!
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Old   January 24, 2013, 05:24
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Any sugestions?
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Old   January 24, 2013, 07:24
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还问,问你妹啊,傻逼!
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Old   January 24, 2013, 07:39
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You can get monitors time history automatically. As you said, Solution/Monitors/cd. Be sure tocheck the "write" box, select a boundary and type a file name. That should solve your problem.
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Old   January 24, 2013, 08:29
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I have done these steps exactly several times, but the results are the same I get only the last time step and CD.
Flow is TRANSIENT.
I thing that this problem is related to calculation activities.
Some other opininions.
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Old   January 24, 2013, 11:26
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Have you tried to open the cd-history file? I open it in matlab, all information should be there.
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Old   January 24, 2013, 11:48
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I open the cd-history.txt with notepad is it any diference i'll open in matlab.
You have succeeded , that all time steps and Cd were saved?
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Old   January 24, 2013, 12:03
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Notepad should work. Mmmmh, what's your timestep and how often do you save a .dat file?
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Old   January 24, 2013, 16:54
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I changing time steps, for example time step size 0.1 s, number of time steps 100, max iterations 30, but the point is that I always get the last time step and the CD.
how often do you save, how to do that.
Can you tell me all your actions, maybe I have missed something, but it hard to believe.
Thanks for a help.
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Old   January 24, 2013, 17:05
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In calculation activities you can say when you want to save your .dat files. If you are doing 100 timesteps, you can save every 10 timesteps. Maybe you haven't saved any .dat files and cd-history.txt is not being updated. Give it a try.
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Old   January 24, 2013, 17:17
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Now I understand that you mean, I have already done that thing, but still it dosn't work as I want.
It's interesting how it works for you.
What else can be important?
What I missed .
Thanks a lot
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Old   January 24, 2013, 17:21
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Have you anything done with solution animations?
You have just created drag monitor and marked write ?
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Old   January 24, 2013, 17:49
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No. I just set the case to transient, choose a model, set boundary conditions, initialize from inlet (most of the cases I do), set the solvers, set calculation activities, solve. Pass me your case file and I can have a look at it.
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Old   January 28, 2013, 03:33
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I have found a solution.
So if you have transient model and you want to get Cd every time step yoo should do these steps.
1) Choose model
2) Set boundary conditions
3) Reference values(Compute from inlet)
4) Choose Solution methods
5) Solution Initialization press initialize and dont choose anything in the field compute from
6) Calculation Activities/Solution animations/create/time step/define/Display type monitor/ statistics choose only delta time/ create drag monitor/ choose write/ ok ok ok
7) Come back to solution initialization choose compute from inlet and initialize
8) Do calculations
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