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2D airfoil Cl and Cd are too high

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Old   June 16, 2010, 09:12
Default 2D airfoil Cl and Cd are too high
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Travis Moulding
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I知 new to CFD and I知 having a problem with Cl and Cd being too large. I知 running a steady state 2D airfoil with the following settings. I'm assuming there is a problem with the ref values but I have set them up the way I have read how to. Any thought would be great

General:
Density-Based, Steady
Models:
Energy On, Viscous- Realizable k-3, Enhanced Wall Fn
Farr field pressure, guage pressure 1525.647 (lb/ft^2)
Mach 0.6
Aoa 2 deg
Turbulence specification method K and Epsilon
Reference values: area 74.11in^2, depth 1in, length 74.11in
Solution method
Forulation: explicit
Flux type: Roe-FDS
Green-Gauss Node Based
Flow: Second Order Upwind
Turbulent Kinetic Energy: Second Order Upwind
Turbulent Dissipation Rate: Second Order Upwind
Solution Controls:
Courant Number: 1
Multigrid Level: 4
Residual Smoothing: Iterations = 0
Under-Relaxation Factors
Turbulent Kinetic Energy = 0.7
Turbulent Dissipation Rate = 0.7
Turbulent Viscosity = 0.9
Solid = 0.9
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Old   June 16, 2010, 09:14
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Mark Bell
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check that your grid scale is ok. if your results are way out this can be a factor.
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Old   June 16, 2010, 09:22
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Travis Moulding
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How do I check the grid scale?
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Old   June 16, 2010, 09:26
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Mark Bell
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from the menu, Mesh -> Scale

you need to check the extents of your domain that they match up the size. Otherwise you will need to expand or contract using the scaling factors.
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Old   June 16, 2010, 09:41
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Travis Moulding
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Thank you mbell10, I checked the scale between Gridgen and Fluent and the scale was off. I corrected it and started recalculating the solution and it seems to be heading in the right direction. Thanks again!
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