[AKdfc]

Good evening!

I was carrying out an analysis trying to validate the flow over the S809 Airfoil against available experimental data.

I have used one of the previous studies which attempted to simulate a fully turbulent flow over the airfoil as a reference to first carry out a verification of my CFD analysis.
The reference paper used was the following:
Wolfe, W. P. and Ochs, S. S., CFD calculations of S809 aerodynamic characteristics, AIAA
paper, 1997, AIAA-97-0973

So far, in line with the study carried out, I used
- A C type grid topology
- The standard k-epsilon turbulence model
- A cell distribution of 300 cells on the surface
- A first cell height ensuring y+ > 30

The pressure distribution and hence the calculated lift coefficient are showing reasonably good agreement.

However, the drag coefficient value is deviating by a large margin (>80%) as opposed to (~50%) in the reference study carried out.
To correct this I tried to change the no of prism layers and the growth rate in the inflation layers and it still seems to have any appreciable effect on the value of the drag coefficient.

Also, I plotted the Turbulent-viscosity-ratio contour to verify whether the regions of the boundary layer have been captured and here, too there seems to be some modelling error. For a y+>30 mesh, it should show a high value of TVR but it is showing a very small value both on the forward portion and the rearward portion of the airfoil.


Any ideas or guidance would be much appreciated.
Thanks

Cp_SM6_chordwise.png

TVR_SM6_Fore_midchord.png

TVR_SM6_Aft_midchord.png