Discussion Forum

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

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 ;)

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Good luck
Ivar

Yes I was … the overall score is definitely in your favor though Ivar ;)

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

i have read the above discussion please tell me how to apply these conditions in comsol 5.0 on SAW device interacting with droplet.

The boundary conditions are ready-made options in fluid flow physics.

L

thank you sir

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?

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,