[otubaba]

Hi Guy,

I am running a 2D simulation on a NACA 0018 airfoil (Spalart Allmaras) , and I am having problem setting up the right Reference values to calculate the lift and drag coefficients. So far, my lift coefficient is lower than that of my experiment and other published works.

Here the values from my experimental set up:

Chord=0.25m, Span=0.3m, velocity=15m/s, AoA=10deg, air density=1.16kg/m3, viscosity=1.89541e-5kg/m-s

I'll be very grateful if anyone can help me solve this problem.

Thanks

[alireza_b]

Hi
it is not necessary related to the reference values.
maybe it is from your solver (turbulence models, grid quality, ...)

notice, if your Re # is transitional, you should use transitions models. however
in this situation, you are far from experimental data.
in this paper explain why this phenomena happens.

M. Serdar Gença,, Ünver Kaynakb, Hüseyin Yapici
Performance of transition model for predicting low Re aerofoil flows
without/with single and simultaneous blowing and suction
European Journal of Mechanics B/Fluids 30 (2011) 218–235

but it seems your reference values is correct.

[otubaba]

Thanks Alireza