# Slip Boundary Condition for Moving Boundary

 Register Blogs Members List Search Today's Posts Mark Forums Read

 November 11, 2005, 08:12 Slip Boundary Condition for Moving Boundary #1 Shukla Guest   Posts: n/a Hi, I am testing my Euler solver for moving cascade case, and have some doubts about the moving wall slip boundary condition. It u and v are x and y velocities and grid moving with velocity 'grid' in y direction, I am assuming that normal velocity in relative frame is zero, is this correct or I have take it in absolute frame. Any guidance would be helpfull. Thanks Shukla

 November 11, 2005, 08:51 Re: Slip Boundary Condition for Moving Boundary #2 ag Guest   Posts: n/a The proper condition is zero mass flow through the boundary. Thus relative to the boundary the fluid has the same normal velocity as the boundary. If the boundary is fixed the normal component of velocity of the fluid is zero.

 November 11, 2005, 09:49 Re: Slip Boundary Condition for Moving Boundary #3 Shukla Guest   Posts: n/a Can you tell me the mathematical formulation, at present I am using Vn = u.nx + (v-vgrid).ny, grid is moving only in y direction. To get the dummy cell variables I use Vdummy = V - 2Vn. Is this correct. Thanks Shukla

 November 11, 2005, 16:02 Re: Slip Boundary Condition for Moving Boundary #4 Mani Guest   Posts: n/a If you are using dummy cells, the formulation is very simple. For a steady boundary you used to specify the dummy velocity such that the average normal velocity on the boundary is zero, and the average tangential velocity is the same as in the interior cell. The flow velocity Vb at the boundary is then Vb = ut*nt +0*nn, where ut is the tangential velocity component of the enterior cell, nt, nn are unit vectors in tangential, normal directions. The dummy velocity Vd to provide this average velocity is always defined by solving Vb = (Vd +V)/2 for Vd, where V is the flow velocity of the interior cell. In the general inviscid case, the normal flow velocity must be equal to the normal velocity of the boundary (which is indeed 0 in the steady case): Vb = ut*nt +ubn*nn, where ubn is the wall velocity (!) in normal direction. As before, Vb = (Vd +V)/2 is solved for dummy velocity Vd. You can figure out for yourself if this is consistent with your formulation.

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post Kelvin_mk OpenFOAM 1 March 15, 2014 05:02 vas FLUENT 11 August 6, 2012 06:36 ashtonJ CFX 4 May 17, 2011 19:07 hemph OpenFOAM Running, Solving & CFD 3 January 18, 2007 06:15 evan FLUENT 0 July 29, 2004 13:37

All times are GMT -4. The time now is 13:30.