# Number of Timesteps and Physical Timescale

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 October 15, 2010, 07:34 Number of Timesteps and Physical Timescale #1 New Member   Niklas Join Date: Sep 2010 Posts: 7 Rep Power: 6 Hey, sorry but i have to ask some very fundamental questions. The first question concerns the physical timescale. What advisements have to be done before i adjust this value? The second question is: Were in Ansys can i adjust the number of timesteps? Under Solver Control in Ansys-Pre, there is only a possibilty to adjust the number of maximum and minimum Iterations. I´m using Ansys 12 in my Project. regards Nick

 October 15, 2010, 07:54 #2 Senior Member   Joshua Counsil Join Date: Jul 2009 Location: Halifax, Nova Scotia, Canada Posts: 366 Rep Power: 9 For your first question: http://www.cfd-online.com/Wiki/Ansys...gence_criteria In Solver Control, you can choose to specify iterations, time, or timesteps.

October 15, 2010, 10:27
#3
Senior Member

Michael P. Owen
Join Date: Mar 2009
Posts: 195
Rep Power: 8
Quote:
 Originally Posted by Leuchte Hey, sorry but i have to ask some very fundamental questions. The first question concerns the physical timescale. What advisements have to be done before i adjust this value? The second question is: Were in Ansys can i adjust the number of timesteps? Under Solver Control in Ansys-Pre, there is only a possibilty to adjust the number of maximum and minimum Iterations. I´m using Ansys 12 in my Project. regards Nick
It sounds like you are doing a steady state simulation. There are no "timesteps", there are only interations. The name "timescale" is somewhate confusing; CFX uses a false transient algorithm in steady state to under-relax the solution as it iterates towards convergence. That's why it's a time "scale" and not a time "step".

For your first question, a good choice is usually a fraction (a third for example) of a representative timescale in the problem, 1/omega for rotating machines, the residence time L/V for through flow problems, etc.

 October 15, 2010, 10:28 #4 Senior Member   Michael P. Owen Join Date: Mar 2009 Posts: 195 Rep Power: 8 Also, Josh, I think you are confusing the Analysis Type settings for transient with the Solver Control settings.

 October 15, 2010, 10:36 #5 Senior Member   Joshua Counsil Join Date: Jul 2009 Location: Halifax, Nova Scotia, Canada Posts: 366 Rep Power: 9 Indeed I am. 18-hour workdays fry your brain.

 October 15, 2010, 10:47 #6 Senior Member   Michael P. Owen Join Date: Mar 2009 Posts: 195 Rep Power: 8 Been there.

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