# Solid body becoming source or sink

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 June 28, 2006, 20:35 Solid body becoming source or sink #1 zonexo Guest   Posts: n/a hi, i'm using the fractional scheme to solve the 2d NS eqn. I found that after solving the poisson eqn, sometimes the body will become a sink (ie it seems to be sucking in the flow velocity ) or a source (ie the flow velocity is flowing out). May I know why this is happening? What is the source of the problem for the above 2 scenario? Tks!

 June 28, 2006, 21:03 Re: Solid body becoming source or sink #2 Jim_Park Guest   Posts: n/a Is this for incompressible flow? What do you expect to happen at the body-fluid interface? If you expect zero-flux (or zero normal velocity) at those surfaces, the Poisson equation boundary conditions on those surfaces need to express that. I don't know "the factional scheme" or how it solves the pressure (Poisson) equation, so that's as far as I can take it. Maybe someone else can add to this ...

 June 28, 2006, 23:22 Re: Solid body becoming source or sink #3 zonexo Guest   Posts: n/a ya, it's for incompressible flow. for stationary body, u=v=0, dp/dn=0. however, I believe there's some error in the implementation of the BC hence resulting in the body changing to a sink or source. I'm wondering if anybody has experience before and therefore know the cause of it....

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