# outlet boudary condition for a flow in the pipe

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 October 28, 2004, 07:08 outlet boudary condition for a flow in the pipe #1 Atit Guest   Posts: n/a I would like to simulate the flow in a circular pipe with a turbine in the pipe. [ I did not model the streamline disturbance by the turbine, I model the turbine as the subdomain with a momentum sink] I specify the inlet boundary condition of the pipe as "Inlet" with a given x-component velocity. For an outlet boundary condition, I think I should specify "Outlet" with an x-component velocity as v2 = rho1*v1/rho2. This v2 comes from the continuity equation for 1D flow. However I saw that in the tutorial about "flow through a butterfly valve" and "flow in a catalytic converter" of CFX, they are all specified the zero relative pressure as the outlet boundary condition. 1. I was wondering about zero relative pressure that when do we use this boundary condition? Should I use it in my case? 2. In "flow in a catalytic converter", I note that it's emphasized that the outlet boundary condition must be static pressure, not average static pressure. Do anyone know why? Thank you very much. Atit

 October 31, 2004, 13:11 Re: outlet boudary condition for a flow in the pip #2 Atit Guest   Posts: n/a In additon, when I set zero total pressure at the inlet of the pipe, what does it mean? When should we use this condition? Thank you. Atit Koonsrisuk

 November 9, 2004, 17:43 Re: outlet boudary condition for a flow in the pip #3 KKA Guest   Posts: n/a all the boundary conditions and their meanings have been documented in the USER MANUAL. Please refer to them!! regards!!