fluent boundary conditions

ashishtbm · May 23, 2013, 08:40

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..

diamondx · May 23, 2013, 13:08

try far-field as inlet...

jziha · May 24, 2013, 09:05

Try to change the size mesh, time step and relaxation factors

MAC88 · May 27, 2013, 04:52

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!!!

neprendo · February 4, 2014, 06:44

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

me3840 · February 6, 2014, 20:42

It may have been his drag definition. Drag is defined relative to the freestream, not the airfoil direction.

May 23, 2013, 08:40	fluent boundary conditions	#1
ashishtbm New Member Ashish Kumar Join Date: May 2013 Posts: 4 Rep Power: 13	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, 13:08		#2
diamondx Super Moderator Ghazlani M. Ali Join Date: May 2011 Location: Tokyo, Japan Posts: 1,385 Blog Entries: 23 Rep Power: 29	try far-field as inlet... __________________ Regards, New to ICEM CFD, try this document --> https://goo.gl/KAOIwm Ali

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May 24, 2013, 09:05		#3
jziha New Member John Ziha Join Date: May 2013 Posts: 3 Rep Power: 13	Try to change the size mesh, time step and relaxation factors

May 27, 2013, 04:52		#4
MAC88 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
neprendo New Member Nick Prendergast Join Date: Dec 2013 Posts: 28 Rep Power: 12	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
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 25	It may have been his drag definition. Drag is defined relative to the freestream, not the airfoil direction.