CL of a 2-D airfoil at AoA

mvle91 · May 12, 2012, 22:46

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, 05:48

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

aswin · June 8, 2012, 03:18

hi..

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, 17:36

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, 04:24

thank you mitchell....

cfd seeker · June 9, 2012, 04:53

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, 06:38

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.

May 12, 2012, 22:46	CL of a 2-D airfoil at AoA	#1
mvle91 New Member Mitchell Le Join Date: May 2012 Posts: 2 Rep Power: 0	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.

June 8, 2012, 03:18	steady or transient case for airfoil simulation...	#3
aswin New Member aswin vudddagiri Join Date: May 2012 Posts: 3 Rep Power: 14	hi.. 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.

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May 15, 2012, 05:48		#2
michalRS New Member Michal Join Date: May 2012 Posts: 7 Rep Power: 14	Did you make sure the reference values are suitable for each calculation?

June 8, 2012, 17:36		#4
mvle91 New Member Mitchell Le Join Date: May 2012 Posts: 2 Rep Power: 0	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.

June 9, 2012, 04:24		#5
aswin New Member aswin vudddagiri Join Date: May 2012 Posts: 3 Rep Power: 14	thank you mitchell....

June 9, 2012, 04:53		#6
cfd seeker Senior Member Join Date: Mar 2011 Location: Germany Posts: 552 Rep Power: 20	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

June 9, 2012, 06:38		#7
aswin New Member aswin vudddagiri Join Date: May 2012 Posts: 3 Rep Power: 14	so can i run steady simulation until the stall occurs??

January 15, 2013, 10:17		#8
shlgzz New Member Wheeler Join Date: Jan 2013 Posts: 24 Rep Power: 13	Increasing the MACH means increasing the RE.It's obvious that the Cl would increase.