[aptahaney]

Hi,
I am using Ansys Fluent to investigate the coefficient of lift for a 2D airfoil for my university thesis. I am very new to Ansys and have followed a number of tutorials online to produce my model. My initial work involves a mesh convergence study, so I have created a number of models with varying meshes containing between 30,000 and 200,000.

Unfortunately, when I run the Ansys Fluent programme to date, I obtain a Cl of approximately 0.45, when the angle of attack is 8 degrees (some of my bigger programmes are still running with over 80,000 iterations). Previous experiments and simulations by others, using similar conditions have achieved Cl values of approximately 0.65 (http://turbmodels.larc.nasa.gov/naca0012_val.html). Furthermore, the previous simulations seem to have achieved this for domains containing between 60,000 and 80,000 nodes. I am no where near this.

Would anyone be able to provide me with any indication why this would be, and how I may resolve it?

(The following are the steps and conditions I have used to date:
- created the geometry in Ansys Geometry, imported to Ansys ICEM.
- The computational domain is similar to this: http://turbmodels.larc.nasa.gov/naca0012_val.html, except I used 50 chord lengths instead of 500.
- I used the following boundary conditions: Velocity Inlet, Pressure Outlet, and symmetry at the upper and lower boundaries.
- Exported the model to Ansys Fluent.
- In the "Models" tab, I used Realizable k-e model, with standard wall functions.
- Calculating Cl for an angle of attack of 8 degrees, a chord length of 1m, Reynolds number of 6 million. Therefore, in the "Boundary Conditions" tab, I used velocity magnitude 87.64 m/s, x-direction flow direction (cos alpha)=.9903 and y-direction flow direction (sin alpha) = 0.1391
- In "Reference Values" tab, I used area = 1 (m2), density of air=1.225 (kg/m3), and viscosity 1.7894e-5 (kg/m-s), temp 288.16K
- "Solution Methods" tab: Simple, and the remainder default.
- "Monitors" tab: Convergence of all residuals at 1e-6
- "Monitors" tab: Cd-1: Force Vector X = 0.9903, Force Vector Y = 0.1391
- "Monitors" tab: Cl-1: Force Vector X = -0.1391, Force Vector Y = 0.9903
- "Solution Initialisation" tab: Compute from Inlet -> Initialise
- Run Calculation)

Apologies about such a long email. I would very much appreciate any help I can have on this, as I have been trying to figure it out for over 2 weeks and seem to be getting no where.

Thanks,

Regards,
Aidan

[aptahaney]

typo in original above: "I obtain a Cl of approximately 0.55" should have said "0.45" - corrected now