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mvle91 May 12, 2012 21:46

CL of a 2-D airfoil at AoA
I have constructed a mesh in ICEM for my NASA (SC) 0410 airfoil and have had my results converge in FLUENT to 1e-6 residuals. I am increasing the Mach number and checking the lift and drag coefficients after convergence. I am finding though that as I increase the Mach number, the coefficient of lift is also increasing. Could anyone help me out as to why the Cl is not remaining constant for the same alpha. My Mach numbers range from .6 to .8 and I am at a constant 2 degrees AoA. I am very new to FLUENT, so don't hesitate saying any answers you might think are obvious. Thanks for the help.

michalRS May 15, 2012 04:48

Did you make sure the reference values are suitable for each calculation?

aswin June 8, 2012 02:18

steady or transient case for airfoil simulation...

I am doing simulation for NACA 0018 airfoil. I considered the flow as a transient and used SST turbulence model. But in many of the papers i have found using steady flow. But how can flow over an airfoil will be steady??

can anyone help me of when to use steady/transient for simulation of airfoil and the flow physics for simulating the airfoil..

Thank you.

mvle91 June 8, 2012 16:36

The flow will be steady with time. Meaning the model will converge on one solution. Flow over an airfoil can be unsteady, but if you are doing an airfoil at typical flight conditions, Ive found the flow to always be steady. I havent done an abundance of models, but that is my two cents.

aswin June 9, 2012 03:24

thank you mitchell....

cfd seeker June 9, 2012 03:53

Flow over the aerofoil becomes unsteady due to large turbulence and flow separation. Flow separation and turbulence is dominant at higher angles of attack especially near stall. So you can run steady simulation at smaller angle of attacks but u can't run unsteady simulation at higher angle of attacks

aswin June 9, 2012 05:38

so can i run steady simulation until the stall occurs??

shlgzz January 15, 2013 10:17

Increasing the MACH means increasing the RE.It's obvious that the Cl would increase.

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