# The end of unsteady flow

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 October 29, 2013, 12:43 The end of unsteady flow #1 Senior Member   Saeed Join Date: Jan 2013 Posts: 177 Rep Power: 5 Hi. I am modeling an unsteady flow in fluent(implicit). With changing the time step, i can achieve to converging, but after converging the iteration is continue, so How can i understand the simulation is done and i can export the results? Thanks __________________ If this post can help, Just click on LIKE

 October 30, 2013, 01:42 #2 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,149 Rep Power: 32 by decreasing (I suppose) the time step size (dt), your solution converges faster FOR A TIME STEP (t). That means the solver switches on next time step (t+dt) untill time step t reaches the number of time steps you set (N) In this example, dt = 5e-5 s N = 2000 That means calculation will be over for t = N * dt = 2000 * 5e-5 = 0.1 s __________________ In memory of my friend Hervé: CFD engineer & freerider

 October 30, 2013, 06:12 #3 Senior Member   Saeed Join Date: Jan 2013 Posts: 177 Rep Power: 5 Thank you for reply 1- In my case, by decreasing the time step size (dt), the residuals are going up and more diverge . 2- I do not anything about the time of ending the flowing in my model, so which time i should stop the processing? __________________ If this post can help, Just click on LIKE

 October 30, 2013, 06:26 #4 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,149 Rep Power: 32 1- weird 2- it depends on what you want to compute (your physics) __________________ In memory of my friend Hervé: CFD engineer & freerider

 October 30, 2013, 06:41 #5 Senior Member   Saeed Join Date: Jan 2013 Posts: 177 Rep Power: 5 Can i stop processing when the results do not change after more iterations? __________________ If this post can help, Just click on LIKE

 October 30, 2013, 07:12 #6 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,149 Rep Power: 32 For sure (you should ask: "Can i stop processing when the results do not change after more time steps") __________________ In memory of my friend Hervé: CFD engineer & freerider

 October 30, 2013, 08:35 #7 Senior Member   Saeed Join Date: Jan 2013 Posts: 177 Rep Power: 5 I am asking: Can i stop processing when the results do not change after more time steps ? __________________ If this post can help, Just click on LIKE

October 30, 2013, 08:44
#8
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Maxime Perelli
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Quote:
 Originally Posted by -mAx- For sure
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In memory of my friend Hervé: CFD engineer & freerider

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