# BCs in staggered grids

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 June 11, 2000, 04:44 BCs in staggered grids #1 Katherine Daru Guest   Posts: n/a Hello, I am a CFD newbie and am attempting to model incompressible 2D flow in a cylinder with SIMPLE and a staggered grid. I have two rather basic questions: 1) How do you handle the no-slip condition at the wall with a staggered grid? Do you interpolate? 2) What is an appropriate velocity BC at the outlet for a specified pressure drop across the cylinder? Obviously I cannot specify the velocity itself, but what do I do with those outer grid points? Thank you in advance for your help - Katherine Daru

 June 15, 2000, 16:07 Re: BCs in staggered grids #2 Sergei Chernyshenko Guest   Posts: n/a Hi, Katherine, 1) How do you handle the no-slip condition at the wall with a staggered grid? Do you interpolate? 1a): By using the no-slip condition in calculating the momentum flux through the wall when we derive the finite-difference equation for the near-wall nodes. 1b) Yes, in a sense. 2) What is an appropriate velocity BC at the outlet for a specified pressure drop across the cylinder? For example, du/dx=0. Mathematically, you can even prescribe u (as far as continuity is satisfied) but du/dx=0 is more realistic. It is not that easy to specify the pressure drop. Specyfying the flow rate is more convenient. Rgds, S.