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Number of Timesteps and Physical Timescale

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Old   October 15, 2010, 07:34
Default Number of Timesteps and Physical Timescale
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Niklas
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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.
Im using Ansys 12 in my Project.

regards
Nick
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Old   October 15, 2010, 07:54
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Joshua Counsil
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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.
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Old   October 15, 2010, 10:27
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Michael P. Owen
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Quote:
Originally Posted by Leuchte View Post
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.
Im 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.
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Old   October 15, 2010, 10:28
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Michael P. Owen
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Also, Josh, I think you are confusing the Analysis Type settings for transient with the Solver Control settings.
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Old   October 15, 2010, 10:36
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Joshua Counsil
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Indeed I am. 18-hour workdays fry your brain.
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Old   October 15, 2010, 10:47
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Michael P. Owen
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Been there.
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