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Slip and No Slip

Posted 8 nov. 2012, 06:49 UTC−5 Computational Fluid Dynamics (CFD), Modeling Tools & Definitions, Parameters, Variables, & Functions Version 4.3, Version 5.2 9 Replies

Lohith Pemmasani
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What is the difference between slip and no slip options in the boundary conditions of laminar flow.

which will be a suitable option to choose for blood flow in capillaries.
9 Replies Last Post 31 mars 2017, 11:12 UTC−4
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago 8 nov. 2012, 09:20 UTC−5
The no-slip boundary condition at a wall is always more accurate. You should use for blood flow in capillaries.

The slip wall condition is for cases where viscous effects at the wall are negligible and/or your mesh size is much bigger than the boundary layer thickness (so you’re not capturing the boundary layer effects anyway). The slip boundary is also the proper boundary condition for symmetry surfaces. You can verify that if you look at the equations COMSOL uses when you select Symmetry boundary condition.

Nagi Elabbasi
Veryst Engineering
The no-slip boundary condition at a wall is always more accurate. You should use for blood flow in capillaries. The slip wall condition is for cases where viscous effects at the wall are negligible and/or your mesh size is much bigger than the boundary layer thickness (so you’re not capturing the boundary layer effects anyway). The slip boundary is also the proper boundary condition for symmetry surfaces. You can verify that if you look at the equations COMSOL uses when you select Symmetry boundary condition. Nagi Elabbasi Veryst Engineering
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, 09:22 UTC−5
Hi

no-slip is the fact that a fluid velocity tends to "0" at the solid-fluide interface, noslip there is no fluid-surface friction at all.

Form most fluid problems, at least in laminar no-slip is rather "normal" in turbulent anyhow there are "tricks" being applied in the surface layer regions, but I tend to use no-slip anyhow.

A slip conditions is as a symmetry condition (check the true equations), the wall has no effect on the fluid velocity in planes parallel and close to the wall


You were first this time Nagi ;)

--
Good luck
Ivar
Hi no-slip is the fact that a fluid velocity tends to "0" at the solid-fluide interface, noslip there is no fluid-surface friction at all. Form most fluid problems, at least in laminar no-slip is rather "normal" in turbulent anyhow there are "tricks" being applied in the surface layer regions, but I tend to use no-slip anyhow. A slip conditions is as a symmetry condition (check the true equations), the wall has no effect on the fluid velocity in planes parallel and close to the wall You were first this time Nagi ;) -- Good luck Ivar
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago 8 nov. 2012, 09:26 UTC−5
Yes I was … the overall score is definitely in your favor though Ivar ;)
Yes I was … the overall score is definitely in your favor though Ivar ;)
Hooman
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Posted: 1 decade ago 18 août 2013, 21:43 UTC−4
Hello,
on No slip wall u,v=0 and you have boundary layer
in slip wall normal velocity is zero but the tangential velocity is not zero (v=0,u is nonzero) and you do not have boundary condition.

I have my own question. anybody knows about dp/dx or dp/dy on a slip wall and no slip wall?

Thanks
Hello, on No slip wall u,v=0 and you have boundary layer in slip wall normal velocity is zero but the tangential velocity is not zero (v=0,u is nonzero) and you do not have boundary condition. I have my own question. anybody knows about dp/dx or dp/dy on a slip wall and no slip wall? Thanks
Imran Shah
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Posted: 9 years ago 10 nov. 2015, 22:53 UTC−5
i have read the above discussion please tell me how to apply these conditions in comsol 5.0 on SAW device interacting with droplet.
i have read the above discussion please tell me how to apply these conditions in comsol 5.0 on SAW device interacting with droplet.
Lasse Murtomäki
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Posted: 9 years ago 11 nov. 2015, 02:02 UTC−5
The boundary conditions are ready-made options in fluid flow physics.

L
The boundary conditions are ready-made options in fluid flow physics. L
Imran Shah
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Posted: 9 years ago 11 nov. 2015, 04:18 UTC−5
thank you sir
thank you sir
Rasaer
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Posted: 8 years ago 31 mars 2017, 10:48 UTC−4
in COMSOL no slip means both u=0 and v=0 for 2D flow, right?

What about at two liquid interface? suppose air is flowing over a pool. what boundary condition is appropriate at the interface? I think slip boundary condition should be fine. And what there is a species transfer across the boundary?

in COMSOL no slip means both u=0 and v=0 for 2D flow, right? What about at two liquid interface? suppose air is flowing over a pool. what boundary condition is appropriate at the interface? I think slip boundary condition should be fine. And what there is a species transfer across the boundary?
Mohammad Amin Kazemi
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Posted: 8 years ago 31 mars 2017, 11:12 UTC−4
Rajib,
In this case, it is usually assumed that the tangential components of velocities in two fluids at the interface are equal. This is a kind of "no-slip" condition since the relative velocity of the fluids at the interface is zero but they can both be non-zero (The fluids move together along the interface).
The normal components are also equal unless evaporation or condensation (mass transfer between the fluids) occur.
Amin,
Rajib, In this case, it is usually assumed that the tangential components of velocities in two fluids at the interface are equal. This is a kind of "no-slip" condition since the relative velocity of the fluids at the interface is zero but they can both be non-zero (The fluids move together along the interface). The normal components are also equal unless evaporation or condensation (mass transfer between the fluids) occur. Amin,

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