2D Flow over cylinder, low lift/drag coefficients

olives03 · August 3, 2009, 10:00

Hello all,

I am currently attempting to determine the lift and drag coefficients for airflow over a single cylinder in both laminar/turbulent flow scenarios using FLUENT.

My issue is that the drag and lift coefficients are much lower than expected, with most analysis giving lower Cd and Cl values (currently working on the laminar case - Re = 100, haven't started on the turbulent yet)

Mesh should not be an issue, I am currently troubleshooting by using a mesh from the previous year that was known to be successful.
I am scaling the grid down from metres to inches, yet in the reference values remain as 'Area' and 'Length' = 1m

I get the feeling that I need to change one or both of these to .0254 to account for my reduction in grid size by .0254 - is this correct, or are there other factors that could cause these low Cd & Cl values?

Any help would be greatly appreciated - I've got a lot on at uni and want to get this project/thesis out of the way.

Regards,

Steve

vmlxb6 · February 11, 2011, 19:05

Hey,

I am also simulating a 2-D flow over a stationary cylinder to determine the Cl and Cd over the cylinder. My question is in the lift coeff formula i.e Cl=F/(0.5*density*U^2 *Area), the area is the projected area i.e length*diameter or the surface area (2*pi*radius*length) ???

Also what values should I put for Depth, Enthalpy, Ratio of Sp. heat in the reference values ???

Is the depth same as diameter of the cylinder ???

August 3, 2009, 10:00	2D Flow over cylinder, low lift/drag coefficients	#1
olives03 New Member Steve Join Date: Aug 2009 Posts: 1 Rep Power: 0	Hello all, I am currently attempting to determine the lift and drag coefficients for airflow over a single cylinder in both laminar/turbulent flow scenarios using FLUENT. My issue is that the drag and lift coefficients are much lower than expected, with most analysis giving lower Cd and Cl values (currently working on the laminar case - Re = 100, haven't started on the turbulent yet) Mesh should not be an issue, I am currently troubleshooting by using a mesh from the previous year that was known to be successful. I am scaling the grid down from metres to inches, yet in the reference values remain as 'Area' and 'Length' = 1m I get the feeling that I need to change one or both of these to .0254 to account for my reduction in grid size by .0254 - is this correct, or are there other factors that could cause these low Cd & Cl values? Any help would be greatly appreciated - I've got a lot on at uni and want to get this project/thesis out of the way. Regards, Steve

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February 11, 2011, 19:05		#2
vmlxb6 Senior Member Ugly Kid Joe Join Date: Aug 2010 Posts: 193 Rep Power: 16	Hey, I am also simulating a 2-D flow over a stationary cylinder to determine the Cl and Cd over the cylinder. My question is in the lift coeff formula i.e Cl=F/(0.5densityU^2 Area), the area is the projected area i.e lengthdiameter or the surface area (2piradius*length) ??? Also what values should I put for Depth, Enthalpy, Ratio of Sp. heat in the reference values ??? Is the depth same as diameter of the cylinder ???