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Oscillatory flow in a pipe

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Old   June 18, 2009, 05:13
Default Oscillatory flow in a pipe
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thomas
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Hi,

I would like to simulate an oscillatory flow crossing a pipe.
I wonder if I have to use periodic boudaries condition (inlet/outlet) or not?
Also can I use a user fonction to define my flow inlet (like: sin(cst*$Time) )?

Thanks in advance.

Tom
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Old   June 18, 2009, 08:10
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Aroon
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Hello Thomas,

I have used a time varying inlet velocity before using the sine function defined as a separate field function and calling the field function as the BC. However in my case, the velocity was always positive and I imposed this velocity as an inlet BC. My function was of the form

V = V0 (2 - sin(w*t))

It worked well. However I have not tried a case with a function where teh flow could go negative, like

V = V0 sin(w*t).
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Old   June 18, 2009, 09:00
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thomas
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Many thanks for your answer. I am using a User field fonction now.

Yes in my case the velocity can be negative. So may be I think I have to use periodic BC but I don't really understand how periodic BC work.

Someone could give me information regarding Periodic BC.

Thanks.
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Old   June 18, 2009, 10:11
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Hello Tom,

To use periodic BC you have to select the two boundaries that are periodic and then define an interface between them. This interface then has to be defined as Periodic and Fully Developed.

But using the periodic BC in STAR CCM+ gives you periodicity in space, not in time.
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Old   June 19, 2009, 05:05
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Hello Aroon,

Many thanks for these information.
In fact, for me periodicity in space is not really clear. I don't understand very well of what it consists.

Thanks.
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