NACA 0012 Coefficient of Lift and Drag Calculations

Antang808 · February 18, 2019, 19:00

Hi everyone,

I've tried a lot of things but I cannot get my airfoil lift and drag coefficients to converge to show what the Xfoil predictions are. I have it operating at parameters:

- Vicious model- Spalart-Allmaras
- Fluid Type cell Zone conditions
- Inlet speed is 8.12 m/s (corresponding to 100K reynolds numbers with my chord length of 0.175m)
- 5 Degrees Angle of Attack
- Specified Shear for side walls
- 0 roughness for airfoil

- Inlet turbulent viscosity ratio = outlet viscosity ratio
- SIMPLE Scheme with Second order Pressure and Momentum with First Order Upwind
- Hybrid Initialization
- 3000 iterations, steady state
-Operating on ANSYS 17.2 but I also have access to ANSYS 18.2

The Cl and Cd plot shows about 3.125 and 0.08 respectively which cannot be correct since Cl should not surpass 1.

Interestingly, the Ratio of Cl/Cd is not far from correct values with my Cl/Cd at about 39 and Xfoil predictions show Max Cl/Cd at about 37.

Does anyone know how to get Fluent to compute the correct values of Cl and Cd?

duri · February 19, 2019, 05:26

Check the reference values. Reference dynamic head or length could be wrong.
Don't use first order scheme unless there are some convergence difficulties.

February 18, 2019, 19:00	NACA 0012 Coefficient of Lift and Drag Calculations	#1
Antang808 New Member Anthony Tang Join Date: Feb 2019 Posts: 7 Rep Power: 7	Hi everyone, I've tried a lot of things but I cannot get my airfoil lift and drag coefficients to converge to show what the Xfoil predictions are. I have it operating at parameters: - Vicious model- Spalart-Allmaras - Fluid Type cell Zone conditions - Inlet speed is 8.12 m/s (corresponding to 100K reynolds numbers with my chord length of 0.175m) - 5 Degrees Angle of Attack - Specified Shear for side walls - 0 roughness for airfoil - Inlet turbulent viscosity ratio = outlet viscosity ratio - SIMPLE Scheme with Second order Pressure and Momentum with First Order Upwind - Hybrid Initialization - 3000 iterations, steady state -Operating on ANSYS 17.2 but I also have access to ANSYS 18.2 The Cl and Cd plot shows about 3.125 and 0.08 respectively which cannot be correct since Cl should not surpass 1. Interestingly, the Ratio of Cl/Cd is not far from correct values with my Cl/Cd at about 39 and Xfoil predictions show Max Cl/Cd at about 37. Does anyone know how to get Fluent to compute the correct values of Cl and Cd?

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February 19, 2019, 05:26		#2
duri Senior Member duri Join Date: May 2010 Posts: 245 Rep Power: 17	Check the reference values. Reference dynamic head or length could be wrong. Don't use first order scheme unless there are some convergence difficulties.