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Why the solution only saves result from the last study step?

Posted 27 févr. 2014, 18:29 UTC−5 Version 4.4 9 Replies

Jing Huang
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Hi, I have a time dependent problem to solve. Because at the start and ending stage of the simulation variables change more significantly, I decide to use several time dependent study steps, for the first and last steps the time step is smaller while in the middle I use a larger dt. In the solvers steps taken by solver is set to be strict. However, I find that at the export, only the time steps in final study step show up in the stored output times, why? In the solvers, I've set Times to Store to be specified values in Output tab. Thanks!
9 Replies Last Post 27 nov. 2014, 06:10 UTC−5
Marino Miccio
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Posted: 1 decade ago 28 févr. 2014, 06:16 UTC−5
Hi Huang,
how and where did you define your different time steps?

Imagine that you need to investigate a time of 10s.
If you want to reduce dt in the first and last second you can use a range like this:
range(0 , 0.01 , 1) range (1 , 1 , 9) range(9 , 0.01 , 10)

Probably you use a wrong setup which overwrite your previous solutions.
Regards.
--
Marino Miccio
Chemical Engineer
marinomiccio.wix.com/home
Hi Huang, how and where did you define your different time steps? Imagine that you need to investigate a time of 10s. If you want to reduce dt in the first and last second you can use a range like this: range(0 , 0.01 , 1) range (1 , 1 , 9) range(9 , 0.01 , 10) Probably you use a wrong setup which overwrite your previous solutions. Regards. -- Marino Miccio Chemical Engineer http://marinomiccio.wix.com/home
Jing Huang
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Posted: 1 decade ago 28 févr. 2014, 14:51 UTC−5
Thank you Marino, that's what I am trying to do. I am attaching a simple examle here in which I used two steps in study 1. It's a very simple diffusion-convection problem. You can see that in Data sets - Solution 1, only the time steps in the second study step are shown. How should I change the setup so the result from step 1 can also be stored?

Thanks!
Thank you Marino, that's what I am trying to do. I am attaching a simple examle here in which I used two steps in study 1. It's a very simple diffusion-convection problem. You can see that in Data sets - Solution 1, only the time steps in the second study step are shown. How should I change the setup so the result from step 1 can also be stored? Thanks!

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Marino Miccio
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Posted: 1 decade ago 2 mars 2014, 09:31 UTC−5
Hi Huang,
I think that the problem is that you insert 2 different time steps.
Try to use only one (STEP 1) with the range set as in the picture and disabling STEP 2.

It should works now.
--
Marino Miccio
Chemical Engineer
marinomiccio.wix.com/home
Hi Huang, I think that the problem is that you insert 2 different time steps. Try to use only one (STEP 1) with the range set as in the picture and disabling STEP 2. It should works now. -- Marino Miccio Chemical Engineer http://marinomiccio.wix.com/home
Jing Huang
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Posted: 1 decade ago 14 avr. 2014, 15:24 UTC−4
Hi, Marino,

You are right, it's easier to set it in your way.

If two different time steps are used in my original setup, in Solver configuration an extra Store Solution node should be added.
Hi, Marino, You are right, it's easier to set it in your way. If two different time steps are used in my original setup, in Solver configuration an extra Store Solution node should be added.
Matej Cerny
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Posted: 1 decade ago 19 nov. 2014, 11:17 UTC−5
Hello,
this is exactly what I was looking for. But I also need to join the data results (time dependent) into one "time serie". Is it possible? Thnaks you Matej.
Hello, this is exactly what I was looking for. But I also need to join the data results (time dependent) into one "time serie". Is it possible? Thnaks you Matej.
Jing Huang
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Posted: 1 decade ago 19 nov. 2014, 11:47 UTC−5
Hi Matej,

If you set your time step in Study Settings as suggested by Marino, all the results of different steps will be in one solution. If you have to use two study steps, then you must add a "Store Solution #" step in your solver. In Results-Data Sets menu, you can right click and select Join to combine them together.

Also, now I realize it's not a good practice to control time step at the study step setting, because here it specifies the solutions to be stored. If you choose very small steps, the final file probably will be too large. Now I only specify those steps I want to store, and control time step size through Time Stepping in Solver settings.
Hi Matej, If you set your time step in Study Settings as suggested by Marino, all the results of different steps will be in one solution. If you have to use two study steps, then you must add a "Store Solution #" step in your solver. In Results-Data Sets menu, you can right click and select Join to combine them together. Also, now I realize it's not a good practice to control time step at the study step setting, because here it specifies the solutions to be stored. If you choose very small steps, the final file probably will be too large. Now I only specify those steps I want to store, and control time step size through Time Stepping in Solver settings.
Matej Cerny
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Posted: 1 decade ago 21 nov. 2014, 04:03 UTC−5
Thanks for reply.

I need more time steps because of different boundary cond. or different "values of variables not solved for". Did you try to join two data sets together? It looks to me like spatial join not join in time.

Thanks for reply. I need more time steps because of different boundary cond. or different "values of variables not solved for". Did you try to join two data sets together? It looks to me like spatial join not join in time.
Ali Adli
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Posted: 10 years ago 27 nov. 2014, 06:09 UTC−5
Hello all,
I am trying to simulate the stress in two steps. first from time t0 to t1 and second from t1 to t2. if I use only the first step and deactivate the second one it works but if I add the second step the results are gone including the time steps. and even the results for the second step is 9 order of magnitude higher than the expected ones. I have tried everything including adding a store solution step but still getting the time range for the second time step only and no results from the first one. Do you have any solution for this?

regards,

ali adli
Hello all, I am trying to simulate the stress in two steps. first from time t0 to t1 and second from t1 to t2. if I use only the first step and deactivate the second one it works but if I add the second step the results are gone including the time steps. and even the results for the second step is 9 order of magnitude higher than the expected ones. I have tried everything including adding a store solution step but still getting the time range for the second time step only and no results from the first one. Do you have any solution for this? regards, ali adli
Ali Adli
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Posted: 10 years ago 27 nov. 2014, 06:10 UTC−5
it is resolved. at least now I have the solution for the first stage.
it is resolved. at least now I have the solution for the first stage.

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