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-   -   Slip & No Slip Conditions (http://www.cfd-online.com/Forums/openfoam/84549-slip-no-slip-conditions.html)

kurne February 2, 2011 07:15

Slip & No Slip Conditions
 
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.

madad2005 February 2, 2011 07:25

To implement no-slip, use:

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

To implement slip, use:

type slip;

kurne February 2, 2011 07:39

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

madad2005 February 2, 2011 07:57

Quote:

Originally Posted by kurne (Post 293258)
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.

kurne February 2, 2011 08:05

Dear mada2005
Thank you very much for guiding me.
Thanks Once Again.

Prash November 20, 2013 13:58

Quote:

Originally Posted by madad2005 (Post 293260)
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.

Sgs August 19, 2016 15:35

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.

Tobi August 24, 2016 06:54

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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