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Slip & No Slip Conditions

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Old   February 2, 2011, 06:15
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, 06:25
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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, 06:39
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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, 06:57
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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, 07:05
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Dear mada2005
Thank you very much for guiding me.
Thanks Once Again.
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Old   November 20, 2013, 12:58
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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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Old   November 1, 2016, 03:19
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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.
Hello
I have a question.In flow with wall slip condition there is one less boundary condition in related to no-slip wall.Why it does not make any problem in terms of deficiency in one boundary condition?
TNX
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Old   September 8, 2018, 22:43
Default with wall function?
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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.
Using a k epsilon model with k and e wall functions as BC, should I use slip or no-slip for U? I mean, i think I need no-sliip because I don't want to model the viscous layer, but I don't know how OF handle it internally.
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Old   November 13, 2018, 01:55
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If you have a wall, the physical behavior is to fix the velocity there, and thus you should use noSlip. The usage of wall-functions does not require to resolve the viscous sublayer. That´s why they were generated. See the book of Wilcox or other literature such as Férziger & Peric.
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Old   December 11, 2018, 18:44
Default Slip Boundary Condition (BC)-Temperature
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Quote:
Originally Posted by Tobi View Post
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.
Hi Tobi,

Though it is an old message, I have a question about that. For a slip BC, I generally choose slip for velocity and zeroGradient for pressure. My question is that for a temperature dependent solver like buoyantBoussinesqSimpleFaom, what BC should I choose for temperature when the wall is considered to slip?

Cheers,
Razon
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Old   June 10, 2019, 04:38
Default noslip means noslip
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From our experience I would say noSlip is not always equivalent to a fixedValue patch. If the surface is moving noSlip imposes the local velocity of the surface on to the fluid next to the patch. This makes it easy to implement a rotating patch which has no fixedValue equivalent.
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Old   July 1, 2019, 07:54
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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.
could any one please help me that how to apply condition for pressure and velocity flow between two plates if the flow is due to the motion of upper plates.(OpenFoam)

2. how to use inletOutlet and outletInlet boundary conditions?can we use both at a time or once at a time?
3.using inletOutlet and outletInletin OpenFoam should we define in both files i.e U ,p
thanks in advance
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Old   July 1, 2019, 07:55
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could any one please help me that how to apply condition for pressure and velocity flow between two plates if the flow is due to the motion of upper plates.(OpenFoam)

2. how to use inletOutlet and outletInlet boundary conditions?can we use both at a time or once at a time?
3.using inletOutlet and outletInletin OpenFoam should we define in both files i.e U ,p
thanks in advance
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