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Unsteady Flow-Time Step Size

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Old   March 5, 2009, 11:50
Default Unsteady Flow-Time Step Size
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Maple
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Hello,

I using unsteady flow option in fluent to solve a non-premixed combustion problem.

I need to define the number of steps and the steps size. The total chamber length is around 250mm and the maximum velocity is around 0.5 cm/s.

Please anyone could tell me what should be the number of steps and the step size, and also the max. number of iteration. How should i calculate them?

Thank you very much.
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Old   March 10, 2009, 09:52
Default Re: Unsteady Flow-Time Step Size
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R Liew
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Hi

The time-step is dependent of the size of the cells. You should take the minimum cellsize in your domain. The timestep is then:

dt = size/speed/4. (courant number around 0.25 with reactions)

this is the maximum dt.

The number of iterations is then: 0.25/0.005/dt.

good luck!

Raoul
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