2D NACA 0012 Steady State Validation
 

I'm trying to validate my mesh in steady state by comparing the values of cl and cd with xfoil prediction from http://airfoiltools.com/polar/detail...0012-il-100000

At AOA 2 degree, xfoil prediction has values of cl and cd at 0.3737 and 0.01444 respectively. However, from the simulation results, I got cl = 0.106 and cd = 0.02.

Chord length = 0.156 m
Inlet velocity = 10 m/s
Density = 1.225 kg/m3
Viscosity = 1.7894e-5 kg/m/s

Pressure-based
SST k-omega model
Velocity inlet and pressure outlet
Periodic matching at the interface
PISO scheme with second order upwind for momentum, turbulent ke and specific dissipation rate
y+ value ranging from 0 to 1.3

I've tried different settings (scheme, low Re correction) to see the differences but it didn't help. I'm not sure what is the cause, maybe I did some mistakes that I'm not aware of. Hope someone could help me out please. :(

The Xfoil transition occurs near TE. It means the solution corresponds to laminar. Force LE transition in Xfoil and compare.

Hi Yao,

I can see two points where the problem can be:

• The SST k-omega turbulence model might be over-predicting turbulence values, hence producing more instabilities than the real ones. As it is a 2-deg AoA analysis and the flow is still attached, I'd strongly recommend you to use Spalart-Allmaras vorticity-based turbulence model
• You're using PISO scheme, and it's usually used for unsteady-state analyses. If I were you I'd change it by SIMPLE scheme, which is much more suitable for this case.

I hope it helped,

Regards.