# fluent boundary conditions

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 May 23, 2013, 07:40 fluent boundary conditions #1 New Member   Ashish Kumar Join Date: May 2013 Posts: 4 Rep Power: 6 Sponsored Links I am using fluent for the first time and I am simulating naca 0012 airfoil under invscid conditions. But I am getting negative values for drag coefficient for angle of attacks around 6-10 degrees. I am using boundary conditions of velocity inlet, pressure outlet and symmetry. Is there any problem in my boundary conditions. My drag direction vector is right pointing towards trailing edge from leading edge. What is the problem, I am unable to identify. Please help me.. Thanks in advance..

 May 23, 2013, 12:08 #2 Super Moderator     Ghazlani M. Ali Join Date: May 2011 Location: Tokyo, Japan Posts: 1,382 Blog Entries: 23 Rep Power: 22 try far-field as inlet... __________________ Regards, New to ICEM CFD, try this document --> https://goo.gl/KAOIwm Ali

 May 24, 2013, 08:05 #3 New Member   John Ziha Join Date: May 2013 Posts: 3 Rep Power: 6 Try to change the size mesh, time step and relaxation factors

 May 27, 2013, 03:52 #4 New Member   Muhammad Aqib Chishty Join Date: May 2013 Location: Islamabad, Pakistan Posts: 23 Rep Power: 0 What is the value of your velocity? Recheck your boundary conditions and your case setup from start. Your case is incompressible or compressible check this too because if flow is compressible then you have to used the Density Based Solver and then turbulence modeling will play the role. Best of luck!!!

 February 4, 2014, 06:44 #5 New Member   Nick Prendergast Join Date: Dec 2013 Posts: 28 Rep Power: 5 I'm having a similar problem with the same aerofoil, do you remember if you got the drag coefficient to become positive and if so, how? thanks Nick

 February 6, 2014, 20:42 #6 Senior Member   Join Date: Nov 2010 Location: USA Posts: 898 Rep Power: 13 It may have been his drag definition. Drag is defined relative to the freestream, not the airfoil direction.

 Tags boundary conditions, naca 0012, velocity inlet face

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