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-   -   Storing data in unsteady simulations (http://www.cfd-online.com/Forums/star-ccm/71067-storing-data-unsteady-simulations.html)

ems December 14, 2009 15:29

Storing data in unsteady simulations
 
Hi all,

I was wondering if it is possible to store a scalar value from one time step to be used in a later time step (or even better, to access data directly from previous time steps). For example, I would like to use a field function that calculates current pressure based on a past pressure value (among other factors).

Thanks,

Eric

Subhadeep December 18, 2009 12:52

unsteady simulation ....
 
Quote:

Originally Posted by ems (Post 239985)
Hi all,

I was wondering if it is possible to store a scalar value from one time step to be used in a later time step (or even better, to access data directly from previous time steps). For example, I would like to use a field function that calculates current pressure based on a past pressure value (among other factors).

Thanks,

Eric

Eric,

StarCCM+ does provide 2nd order temporal resolution for unsteady simulations. What it means is that always the present solution is based on 2nd order forward prediction using the last two time step results. The time step and the number of inner iterations is under user's control. So based on your simulation's physical state you have to choose a small enough time step and also the number of inner iteration so as the solution is really the physical solution if started from your initial solution.

You may want to prove solution independency 1st with time step and then with the same time step but by varying the number of inner iterations.

now with saving unsteady scalar variables you have to do a bit of work I think. If its a particular section or region you can use point, line or even plane and then write a small macro and write the tabulated data out in a directory after every time step. Then you can do whatever you want to do with that data outside in some other post processing tools you use.

Remember to let the run the unsteady simulation for some time to wash away the initials before you start collecting the data at your specific location.

jelon March 26, 2010 09:34

I want to use Field function to make it ,but failed!

Maddin April 3, 2010 06:55

I didn't tried it, but I would try to use a plot as a table via import/export?!


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