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Old   January 21, 2015, 23:18
Unhappy low-medium Reynolds number
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studen
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Hi,

i am trying to slove a low reynolds number flow problem on NACA 4415 (Re 2e5), i am having lot of difficulties in validating with the previous experimental values. currently using SA turbulence model and aoa range is from 0 to 20 deg, the lift is not exactly matching and the drag is over predicted. I am currently using Fluent 14.5 and Fluent 15.0 can you please suggest which turbulence model will be best suited to get closer results to experiment. Further more i am planning to study the 3D effects later.

Thanks for the help
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Old   January 22, 2015, 00:02
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Lean ("Eric") Fang
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Hi,

You might want to try k-omega SST model with low-Re correction. And also make sure that your mesh is well-resolved at boundary layers, and leading & trailing edges.

Hope this helps,
Eric
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Old   January 22, 2015, 00:17
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thanks for the reply

eric,

i have tried all the 2 equation 4 equation transition but the best results are given by SA i dont know why SA offers closer solution to the expt, but the only deal breaker is the increase in drag by 18%
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Old   January 22, 2015, 01:25
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Hi,

May I know which literature you are comparing your simulation results with?

From my own experience dealing with low-Re airfoil simulations, the free-stream turbulence properties play a huge role in the overall aerodynamic behavior, so you need to make sure your simulation free-stream turbulence properties set at the inlet/farfield b.c. are identical to that of the experiments.

Hope this helps,
Eric
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Old   January 22, 2015, 01:35
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C. Ostowari and D. Naik, “Post Stall Studies of Untwisted Varying Aspect Ratio Blades With an NACA 4415 Airfoil Section—Part I,” Wind Engineering, vol. 8, no. 3, pp. 176–194, 1984
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