[mme1998]

Good Afternoon All!

I'm new to CFD and experiencing a couple of issues. I've read up on many topics and used this forum a lot and my knowledge has improved a great deal.

I'm aiming to simulate an NREL S809 aerofoil. First I'll validate my CFD model against experimental data and then simulate a slotted aerofoil.

I've got relatively good agreement for some results, but I'm struggling with stall and drag.

The stall point is at too high an angle of attack and CL. Also the drag values appear to be low, and nowhere near the right value at a CL of less than 0.2

I've gone through the following process:

Geometry
- 600mm chord S809 aerofoil that is 10mm thick
- Plain aerofoil, sharp TE

Mesh
- Around 400,000 elements and 130,000 nodes
- Inflation layer around the aerofoil with 22 layers, first layer thickness gives a y+ of less than 1 over the aerofoil
- Sharp TE causing some issues with inflation, stair-stepping, not sure how to resolve this though?
- Unstructured, I shall be modelling more complex geometry after this validation, so trying to get results with unstructured
- Element size of 3mm on aerofoil surface, gives about 400 divisions around the 2D contour of the aerofoil

Setup
- Using SST turbulence going by other peoples experiments
- Steady-state simulation
- 30 m/s freestream
- Air as an ideal gas at 15 degC, isothermal
- Angle of attack given by inlet cartesian coordinates

I've attached some photos of results and my mesh

Any guidance, ideas or info would be much appreciated!

[ghorrocks]

Your results are heading in the right direction, but you need to do some validation and verification now. See the FAQ for some starting tips: https://www.cfd-online.com/Wiki/Ansy..._inaccurate.3F

In particular you should now look at doing sensitivity analyses on convergence criteria and mesh size, and/or work out your discretisation errors. See the FAQ.