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turbulent velocity profile model ?

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Old   February 10, 2006, 04:33
Default turbulent velocity profile model ?
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cfdq
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I model a turbulent pipe flow which Re=5000 geometryvc3d 0 54.5 20 0 360 72 0 3862 500 using csys 2) at the inlet boundary W=-0.689025(for adjusting Re=5000) and turbulent intensity=0.05 turbulent length=0.001 Another setting is outlet boundary. also I give the geometry scalar factor=0.001(pipe radius =54.5 mm) so final result is as symbol "3" as following web site:

http://www.wretch.cc/album/show.php?...1139464550&p=1

but what I want is trublent velocity profile as following web site

http://www.wretch.cc/album/show.php?...1139464458&p=0

can anyone help me?
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Old   February 13, 2006, 06:23
Default Re: turbulent velocity profile model ?
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Yacine
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use a longuer pipe in the streamwise direction or periodic boundary conditions and you will eventually end up with the profile you want after the solution is converged!!!!
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Old   February 13, 2006, 10:49
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cfdq
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where to use periodic condition? In the theta direction?
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Old   February 13, 2006, 12:04
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cfdq
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do you locate the wall boundary at the R(r)=Radius. or just treat it as defaults setting and needn't to set the wall boundary at the R(r)=Radius. thank you.
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Old   February 13, 2006, 17:26
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Alex
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Not sure what you mean by that last post.

Periodic boundary = Cyclic in STAR-CD language. You need a cylinder with cyclic boundaries on each end, so what goes out one end, comes in the other (or a longer pipe). Also, keep reducing your convergence tolerance. The changes on a iteration by iteration basis will be very small, so the default tolerance may be too large.
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Old   February 13, 2006, 21:43
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cfdq
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can it use cyclic condiction in the z direciton in csys 2 (cylinder coordinate).using cyclic condition must be periodic repeating phenomenon.but pipe flow velocity is changing along the pipe(z direction) .does it work ?
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Old   February 13, 2006, 22:04
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cfdq
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you mean orginal Max Residual Tolerance=0.001 .change it to 0.0001 (smaller).?
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Old   February 14, 2006, 06:08
Default Re: turbulent velocity profile model ?
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Anton Lyaskin
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Actually it should be done in a bit different way - see Methodology, p. 5-8. What you need is a sector mesh (with cyclic boundaries in theta direction), only one cell long along the axis. At "inlet" you should apply uniform pressure and at outlet you should apply mass flow rate.
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Old   March 6, 2006, 15:20
Default Re: turbulent velocity profile model ? *NM*
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asmaa ahmed
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