# A general question on solving NS equations with an ALE description

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 July 22, 2011, 05:26 A general question on solving NS equations with an ALE description #1 Senior Member   Join Date: Jun 2010 Posts: 111 Rep Power: 14 Hi, Just a general question about the ALE approach. In the ALE approach you have both the mesh velocity and the flow velocity and therefore an extra unknown has been added to the NS equations. Is an extra equation needed to solve the equations now and what would that equation be? Thanks, H

 July 23, 2011, 18:08 #2 Member   private Join Date: Mar 2009 Posts: 74 Rep Power: 16 The mesh velocities (magnitude and direction) are input to the fluid motion equations. You have to prescribe those velocities. You can specify values appropriate for your problem or use appropriate physics (boundary motion, acceleration, ???) to specify an equation of motion for the mesh points.

 July 23, 2011, 18:54 #3 Senior Member   Join Date: Jun 2010 Posts: 111 Rep Power: 14 Thanks very much. I have seen a few relationships and am confused by them a little. What I was thinking about was to use this relationship: dv/dL = constant, where L is the cell length. But I'm not sure maybe I should use: dv/dt = constant, Or dL/dt = v(t=n) - v(t=n+1), Or that the cells are increased or decreased in size by the same amount such that dL/dt = constant i.e. v = constant. I would appreciate you help. Thanks, H

 August 7, 2011, 07:18 Initial conditions for an unsteady flow problem in 1D #4 Senior Member   Join Date: Jun 2010 Posts: 111 Rep Power: 14 I was going to post a new question and accidentally wrote here. Please ignore this... Last edited by Hooman; August 7, 2011 at 07:19. Reason: wrong place

 September 5, 2011, 19:47 unsteady flow - issue with for loop #5 Senior Member   Join Date: Jun 2010 Posts: 111 Rep Power: 14 I was going to post a new question and accidentally wrote here. Please ignore this... Last edited by Hooman; September 5, 2011 at 20:12.