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Laminar and turbulent flow in pipes

Posted 7 nov 2012, 16:46 GMT-5 Version 4.2a 4 Replies

Asal Bidarmaghz
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Hi All,
I am trying to model fluid flow and heat transfer in a pipe for different fluid velocities. for Reynolds numbers < 2300 I use navier-stokes equations for laminar flow and for Re>2300 I use RANS (Reynolds average NS) for turbulent model.
the problem is that for 2000<Re<2500 if I run the model both in laminar and turbulent to have some overlaps to chekc the model and I get to very different outcomes and the laminar one in significantly higher that thew turbulent.
i would appreciate if you please help me with this.
4 Replies Last Post 9 nov 2012, 01:46 GMT-5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 8 nov 2012, 02:07 GMT-5
Hi

have you checked that your results are mesh independent ?
particularly in this intermediate regime

--
Good luck
Ivar
Hi have you checked that your results are mesh independent ? particularly in this intermediate regime -- Good luck Ivar
Asal Bidarmaghz
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Posted: 1 decade ago 8 nov 2012, 16:38 GMT-5
Hi Ivar,
yes I have done mesh analysis on that and meshing looks fine.
the model is mesh dependent but based on the mesh analysis results apparently I am using enough elements.

thanks
ASAL
Hi Ivar, yes I have done mesh analysis on that and meshing looks fine. the model is mesh dependent but based on the mesh analysis results apparently I am using enough elements. thanks ASAL
Asal Bidarmaghz
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Posted: 1 decade ago 8 nov 2012, 19:24 GMT-5
Hi Ivar,
now I am trying to use the new feature low reynolds number solver but even for a small model it takes ages and finally an error occurs. it is said in manual that in a pipe flow if you check the delta W+ and it still equal to 11.06 then the model should be fine. I get 11.06 but results are very strange to me.

thanks
ASAL
Hi Ivar, now I am trying to use the new feature low reynolds number solver but even for a small model it takes ages and finally an error occurs. it is said in manual that in a pipe flow if you check the delta W+ and it still equal to 11.06 then the model should be fine. I get 11.06 but results are very strange to me. thanks ASAL
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 9 nov 2012, 01:46 GMT-5
Hi

I agre CFD is a world of itself I'm not an expert here, but there are others out there who are, maybe they could help too ;)

--
Good luck
Ivar
Hi I agre CFD is a world of itself I'm not an expert here, but there are others out there who are, maybe they could help too ;) -- Good luck Ivar

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