# Does Fluent always need inlet and outlet ?

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March 3, 2014, 10:27
Does Fluent always need inlet and outlet ?
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Jochem Grietens
Join Date: Nov 2013
Location: Belgium
Posts: 16
Rep Power: 5
Hi,

I'm simulating a 2D airfoil. I have done my meshing in ICEM end succesfully exported it to fluent. I created an outer boundary called FF(farfield) but i want the flow to hit the airfoil under an angle. So to what type do i set my FF(outer boundary). I tried setting it to "inlet" but this isn't working. So my question is : do i need to specify an inlet and an outlet ?
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 March 3, 2014, 10:37 #2 Senior Member     Daniele Join Date: Oct 2010 Location: Italy Posts: 998 Rep Power: 17 Not sure what you are asking specifically; but think about having a domain with only inlet(s); if you set a velocity inlet, for example, without any outlet, your pressure inside the domain will raise till divergence.. So, if you have a inlet, you need also an outlet.. Daniele

 March 4, 2014, 12:18 #3 Senior Member   Andrew Kokemoor Join Date: Aug 2013 Posts: 122 Rep Power: 7 Technically, you can use velocity-inlet conditions to specify a velocity out of the domain, serving as an outlet; I'm guessing this is what you're trying to do. This overspecifies momentum (a subtle problem, but you definitely won't get good drag results) and underspecifies pressure, which is what's giving you the error. Pressure needs to be specified somewhere in the domain, because the NS equations only solve the pressure gradient. The short answer is to use a pressure-outlet condition, which will solve both of these problems.

 March 5, 2014, 07:43 #4 New Member   Nick Prendergast Join Date: Dec 2013 Posts: 28 Rep Power: 5 depending on how your simulations go and if you're thinking of doing another aerofoil you might want to consider following this tutorial, its a step by step guide on how to build and mesh an aerofoil in Icem. http://www.youtube.com/watch?v=EknKVAJGEJ8 and the short answer is yes, if you want flow into your system you need flow out of your system and vice versa.

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