# boundary conditions

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 August 14, 2003, 11:12 boundary conditions #1 hedonists Guest   Posts: n/a Is it possible to use this set of boundary conditions in Fluent for 2D pipe flow: Pressure inlet and constant mass flow rate?

 August 14, 2003, 12:41 Re: boundary conditions #2 cfdweirdo Guest   Posts: n/a For compressible flow: Total Pressure inlet & Static Pressure outlet or Mass Flow Inlet & Static Pressure Outlet For incompressible flow: Velocity inlet & outlet condition

 August 15, 2003, 01:19 Re: boundary conditions #3 mateus Guest   Posts: n/a Hi! I'm not shure what you want. Maybe you have the same problem as me...I have a known upstream pressure and velocity, but in Fluent you can't define both parameters on inlet bc. What I do is I define velocity inlet and pressure outlet (upstream pressure - pressure losses in pipe), and after simulation converges check if the pressure on inlet agrees with experimental one. It's a bit awkward solution but I think most of the people with this problem solve it this way... regards MATEUS

 August 15, 2003, 10:38 Re: boundary conditions #4 hedonists Guest   Posts: n/a Thanks all. I am suprised that Fluent doesn't have a constant mass flowrate outlet boundary condition.

 August 17, 2003, 04:58 Re: boundary conditions #5 thomas Guest   Posts: n/a I think the outlet boundary condition 'outflow' may help you for your problem and get constant mass flow rate. thomas

 August 17, 2003, 20:54 Re: boundary conditions #6 zhsnaky Guest   Posts: n/a constant mass flow rate is controled by approciate pressure. this may be the reason for no boundary conditions of constant mass flow rate in fluent software.

 August 20, 2003, 05:23 Re: boundary conditions #7 jieremy Guest   Posts: n/a Note that outflow boundaries cannot be used in the following cases: if a problem includes pressure inlet boundaries; use pressure outlet boundary conditions (see Section 6.8) instead

 August 21, 2003, 13:31 Re: boundary conditions #8 hedonists Guest   Posts: n/a For non critical flow, the mass flow rate is governed by both inlet and outlet pressures. To obtain a constant mass, it seems that I should use constant pressure inlet and try-and-error outlet pressure. Is this a correct way?

 August 21, 2003, 20:24 Re: boundary conditions #9 jieremy Guest   Posts: n/a for the compressible flow,you can use these boundary condition:"Mass Flow Inlet & Static Pressure Outlet " then you have made the mass flow as a constant when you define the "Mass Flow Inlet".

 August 24, 2003, 23:37 Re: boundary conditions #10 hedonists Guest   Posts: n/a To be clear, the conditions I have are: constant mass flow rate and constant inlet pressure. But I don't know the downstream pressure. The question was: How to set the boundary conditions?

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