# Multiple inlets with different temperatures in compressible flow, boundary condition

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 July 20, 2016, 00:15 Multiple inlets with different temperatures in compressible flow, boundary condition #1 Member   Join Date: Oct 2013 Posts: 92 Rep Power: 12 Hi, I have a very basic question, what should be the outlet boundary condition if I have multiple inlets with different fluid velocity and temperature? I am currently using something like this Code: ```Inlet0 { type fixedValue; value uniform 1000; } Inlet1 { type fixedValue; value uniform 300; } Inlet2 { type fixedValue; value uniform 300; } outlet { type inletOutlet; value 300; inletValue 300; }``` my solver is rhopimplefoam. is that OK? Any corrections welcome.

 July 24, 2016, 14:44 #2 Senior Member   Join Date: Sep 2010 Posts: 226 Rep Power: 16 Hi, It depends on what you need to do exactly.. regards, T.D.

August 4, 2016, 10:13
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 Originally Posted by T.D. Hi, It depends on what you need to do exactly.. regards, T.D.
I just want a simple mixing of two streams which have different velocity and temperature.
(interested in mixing pattern)

I don't much care for the outlet as long as it is consistent.

 August 4, 2016, 10:23 #4 Senior Member   Join Date: Sep 2010 Posts: 226 Rep Power: 16 Hi, you can use "type zeroGradient" for velocity at outlet, and for pressure: outlet { type fixedValue; value uniform 0; } Good Luck regards, T.D.

August 4, 2016, 10:37
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 Originally Posted by T.D. Hi, you can use "type zeroGradient" for velocity at outlet, and for pressure: outlet { type fixedValue; value uniform 0; } Good Luck regards, T.D.
Thanks TD,

But does uniform 0 pressure makes sense?

because the pressure is physical pressure isn't it? I have kept outlet as 1 atm, same as internalfield and velocity is as you have mentioned.

But I am not so sure about temperature.

June 12, 2018, 17:39
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 Originally Posted by fedvasu Thanks TD, But does uniform 0 pressure makes sense? because the pressure is physical pressure isn't it? I have kept outlet as 1 atm, same as internalfield and velocity is as you have mentioned. But I am not so sure about temperature.
Old thread of mine, now I know more.

Whenever in doubt use zeroGradient for velocity and other scalars(temeprature, species mass fractions etc) for outlet.

and fixedValue for pressure for the outlet.(typically ambient pressure).

 Tags rhopimplefoam, temperature bc