# partial slip to moving wall

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 August 29, 2017, 07:17 partial slip to moving wall #1 Member   Ashok Join Date: Feb 2017 Posts: 31 Rep Power: 9 Hello everyone, can any one tell me how to apply partial slip BC to a wall moving with velocity(say for ex.-0.6679 vertically down). I have defined BC of moving wall like below in U field. in U field: movingWall { type partialSlip; value uniform (0 -0.6679 0); valueFraction uniform 0.5; } in P field: movingWall { type zeroGradient; } If I define velocity as mentioned in U field above, the wall doesnt take any velocity. Only if fixed value is assigned like this, wall is moving. movingWall { type fixedValue; value uniform (0 -0.6679 0); } Any kind of help is appreciated. Thanks in advance.

 August 30, 2017, 16:26 #2 Member   Yousef Join Date: Feb 2015 Posts: 40 Rep Power: 11 For many boundary conditions, the "value" entry specified in the boundary condition is just an initial value and I believe this is the case for the partial slip as well. This is not the case for the fixedValue where OpenFOAM imposes the value according the the "value" entry in the boundary condition throughout the simulation. I think this explains your observation. I don't know how you can apply partial slip on a moving wall though. Regards,

August 30, 2017, 16:57
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Ashok
Join Date: Feb 2017
Posts: 31
Rep Power: 9
Quote:
 Originally Posted by ykanani For many boundary conditions, the "value" entry specified in the boundary condition is just an initial value and I believe this is the case for the partial slip as well. This is not the case for the fixedValue where OpenFOAM imposes the value according the the "value" entry in the boundary condition throughout the simulation. I think this explains your observation. I don't know how you can apply partial slip on a moving wall though. Regards,
Thank you for your Respose. I still couldn't find out how to implement partial slip to a moving wall. One can apply partial slip to a fixed wall in which fluid flows.

But in my case it is reverse. Fluid is filled in a cylindrical tube closed an bottom and side walls are moved with some velocity. So I wanted to give velocity and partial slip at the same time to my wall.

 March 3, 2018, 12:55 #4 Member   vishal Join Date: Mar 2013 Posts: 73 Rep Power: 13 Hello Ashok, I am also trying the same thing. Did you figure out how to implement it?

 March 8, 2018, 10:37 #5 Senior Member   Saideep Join Date: Apr 2015 Location: INDIA Posts: 203 Rep Power: 11 May be I am completely wrong but I am trying to understand how this can be done. Partial Slip: means the wall is stationary but the wall cell faces can have a non-zero velocity. Impact: reduces/ relaxes large magnitudes of viscous forces/ stresses on the boundary cells. Is the analogy not same considering a moving wall with a no-slip boundary condition? That is (please correct me if wrong), there are only two possibilities but not sure what happens. Either the parabolic flow profile is violated, else as above the viscous forces reduce in magnitude. I somehow get a feeling that movingWall with slip can be dealt by just using slip/ partial slip.

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