# Simple Outlet Question

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 June 14, 2010, 16:47 Simple Outlet Question #1 Member   Matt Join Date: Jun 2010 Location: Texas Posts: 31 Rep Power: 9 Sponsored Links I am attempting to execute a simple test case using the icoFoam solver and have encountered a presumably easy problem that I cannot figure out. The mesh of the test case is a cylinder with a L-W ratio of 10:1. The inlet and outlet are on opposite faces of the cylinder. The inlet is given a relatively small initial velocity. What should the boundary field conditions of the outlet be? I have attempted setting the velocity as zero and zeroGradient, and pressure as zeroGradient; however, those conditions return the following error: Code: ```Continuity error cannot be removed by adjusting the outflow. Please check the velocity boundary conditions and/or run potentialFoam to initialise the outflow.``` The test case only runs when the boundary field condition of the outlet is given a velocity greater than zero. best regards, Matt

 June 15, 2010, 01:09 #2 Member   Alan Russell Join Date: Aug 2009 Location: Boise, Idaho USA Posts: 61 Rep Power: 10 Matt, The basic setup is to define the velocity value at the inlet (i.e. type fixedValue; value uniform (2 0 0) and set velocity as zeroGradient at the outlet. For pressure, use zeroGradient at the inlet and a constant value of 'type fixedValue; value uniform 0;' at the outlet. For a good example, look in the pitzDaily tutorial (tutorials/incompressible/simpleFoam/pitzDaily). The airFoil2D and pitzDailyExptInlet tutorials have similar setups - the last one has an inlet velocity profile. I hope this helps, Alan

 June 15, 2010, 11:20 #3 Member   Matt Join Date: Jun 2010 Location: Texas Posts: 31 Rep Power: 9 Hi Alan, Thank you very much for you response. My issue was the pressure at the outlet. I will also look at the tutorials that you mentioned. best regards, Matt

 June 25, 2010, 01:44 #4 Member   Join Date: Jun 2010 Posts: 33 Rep Power: 9 Hi Foamers, Just a quick question. When setting inlet velocity as fixed value. you have to type type fixedValue; value uniform (0 0 0); What im curious about is the uniform part. If i put (2 0 0) does that mean 2m/s in x? So if i have an angled inlet, should I use the components of the XY velocity? Also one can choose to use inletflowRateVelcoityInlet correct? so when i type the flow rate. that does not have to be the components right? What are the differences between those two?! Thanks in advance! Cheers, Terence

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