# Pressure boundary & buoyancy

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 October 22, 2002, 05:29 Pressure boundary & buoyancy #1 Bouke Guest   Posts: n/a Sponsored Links Dear all, I have a question concerning incompressible flow with buoyancy. If I have a vertical outlet plane (pressure boundary) in a case where gravity is included in the equations (e.g., to model natural convection), is it OK to set a constant relative pressure (e.g., 0 Pa) along the outlet or should I correct for the pressure gradient (rho*g*h)? In my code, the pressure boundary is set by fixing the value of the pressure to a given value for each cell of the outlet. I have seen in commercial codes that you can specify an "average" pressure at an outlet; does anybody know how this is implemented? Thanks, Bouke

 October 22, 2002, 06:08 Re: Pressure boundary & buoyancy #2 D.M. Lipinski Guest   Posts: n/a Bourke, Define your pressure, p, in the Navier-Stokes equations, as the static pressure minus hydrostatic pressure. I.e. use the difference, density minus the reference density in the buoyant term. Then you can use the boundary condition p=0 on the outlet. regards DML

 October 22, 2002, 11:37 Re: Pressure boundary & buoyancy #3 Bouke Guest   Posts: n/a OK! I thought that would be difficult to implement but the opposite is true & it works like a charm. Thanks!

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