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velocity profiles of pipe and annulus

Posted Aug 17, 2011, 4:53 a.m. EDT 4 Replies

Michael Rembe Certified Consultant
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Hi,

I have bad convergence using a constant velocity (v=Q/A) for a pipe inflow.

Using a parabolic velocity profile I get excellent convergence! The formula is v=2*Q/A*(1-r^2/R^2) with:
r - space coordinate of an axisymmetrical model
R- pipe radius

Does anybody know the formula of the velocity profile of an annulus (axisymmetrical model)?

Thanks
Michael
4 Replies Last Post Aug 18, 2011, 2:37 a.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Aug 17, 2011, 6:14 a.m. EDT
Hi

in laminar regular flow for an isotropic model its approaching a parabola, that explains probably why you get a better convergence starting closer to the final solution

--
Good luck
Ivar
Hi in laminar regular flow for an isotropic model its approaching a parabola, that explains probably why you get a better convergence starting closer to the final solution -- Good luck Ivar
Michael Rembe Certified Consultant
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Posted: 1 decade ago Aug 17, 2011, 6:24 a.m. EDT
Hi Ivar,
yes, this is right. But now I'm looking for a velocity profile (laminar flow) for an annulus (two pipes into one another).

The formula should be similar to v=4*v_max*s*(1-s) in 2D, but just for a 2d-axisymmetric model

Michael
Hi Ivar, yes, this is right. But now I'm looking for a velocity profile (laminar flow) for an annulus (two pipes into one another). The formula should be similar to v=4*v_max*s*(1-s) in 2D, but just for a 2d-axisymmetric model Michael
Lechoslaw Krolikowski
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Posted: 1 decade ago Aug 17, 2011, 1:55 p.m. EDT
Hi Michael,
Attached is the velocity profile you are looking for.
BR
Andrzej
Hi Michael, Attached is the velocity profile you are looking for. BR Andrzej
Michael Rembe Certified Consultant
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Posted: 1 decade ago Aug 18, 2011, 2:37 a.m. EDT
Hi Andrzej,

thank you very much for the velocity profile!

Best regards
Michael
Hi Andrzej, thank you very much for the velocity profile! Best regards Michael

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