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Slip & No Slip Conditions

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Old   February 2, 2011, 07:15
Default Slip & No Slip Conditions
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Dear All
Will anybody please tell me how to give the Slip and Noslip conditions at the wall.I am bit confused, whether slip means zeroGradient and Noslip means fixedGradient.
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Old   February 2, 2011, 07:25
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To implement no-slip, use:

type fixedValue;
value (0,0,0);

To implement slip, use:

type slip;
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Old   February 2, 2011, 07:39
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Dear madad2005
Thanks A lot for help.Will you please correct me
For No Slip conditions
1) For velocity
type fixedValue;
value uniform 0;
2) For pressure
type fixedValue;
value uniform 0;
For Slip Conditions
1) For velocity
type slip;

2) For pressure
type slip;

Thanks In Advance
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Old   February 2, 2011, 07:57
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Quote:
Originally Posted by kurne View Post
Dear madad2005
Thanks A lot for help.Will you please correct me
For

No Slip conditions
1) For velocity
type fixedValue;
value uniform (0,0,0);

2) For pressure
type zeroGradient;

For Slip Conditions
1) For velocity
type slip;

2) For pressure
type zeroGradient;

Thanks In Advance
See above. The BC requirement for pressure at the wall is normally zeroGradient. For velocity with a slip wall, there are two different conditions to be met normal to the wall and parallel to the wall, which I believe the slip boundary condition handles.
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Old   February 2, 2011, 08:05
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Dear mada2005
Thank you very much for guiding me.
Thanks Once Again.
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Old   November 20, 2013, 13:58
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Quote:
Originally Posted by madad2005 View Post
See above. The BC requirement for pressure at the wall is normally zeroGradient. For velocity with a slip wall, there are two different conditions to be met normal to the wall and parallel to the wall, which I believe the slip boundary condition handles.
Hi all,
sorry to revive such an old post.
1. If I use full-slip for velocity, is there a need to specify pressure ? I guess it should calculate using the velocity at the wall ?

2. What if I use pressure bc as "slip" as well with Velocity bc as "slip" . It should be same as pressure bc "zeroGradient" ? I do not get same answers if I do this.
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Old   August 19, 2016, 15:35
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1. Yes, I think you generally need to specify zeroGradient, but you're right sometimes depending on the solver the 'boundary condition' for pressure is pre-determined by the velocity boundary conditions.
2. I think slip might be sort of a vector boundary condition (different equations for different vector components), and since pressure is a scalar maybe it took the first condition of slip (which could be the no penetration equation u1=0) as the pressure boundary condition instead of d u2 / dn = 0.
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Old   August 24, 2016, 06:54
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An old topic, isn 't it Sgs?

noSlip is a vector class and hence it can not be used for the pressure. noSlip is similar to fixedValue uniform (0 0 0);

The slip boundary condition is a template class and therefore we can use any kind of fields. If we have a scalar it will set it to zeroGradient (I did not check this out, so it is just a logical consequence). For a vector field, the normal component should be zero (sliding). It would be a wall (no fluxes can pass) but there is finally no shearing based on the fact that we assume that there are no viscous effect.
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