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March 4, 2019, 14:46 |
NACA 0012 low speed validation problem
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#1 |
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Hi everyone,
I am modelling a NACA 0012 airfoil using CFX at velocity 1.15 m/s, 1.55 deg AoA in air at 20 deg C (Re = 76104), but I am having issues validating the drag coefficient at this velocity as there seems to be about a 35% error when compared to NASA validation. The lift coefficient validates quite well. I have been using this for validation: https://turbmodels.larc.nasa.gov/naca0012_val.html Re for NASA validation = 6 million Am I using the wrong validation due to these differences in Re? Thank you! Last edited by 35matt215; March 4, 2019 at 17:24. |
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March 4, 2019, 17:09 |
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#2 |
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Glenn Horrocks
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Re = 76000 is likely to be a transitional flow, with turbulence transitional the rear half of the foil or maybe fully laminar flow. That depends on the exact airfoil, upstream conditions, surface roughness and so on.
Re = 6M is definitely fully turbulent over the whole airfoil. They do not look like a good match to me.
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March 4, 2019, 17:19 |
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#3 |
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Thanks for your reply!
So do you think it would be best if I look for papers with a smaller Re in order to validate my model with? |
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March 4, 2019, 18:44 |
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#4 |
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Glenn Horrocks
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Reynolds number is probably the most fundamental parameter in fluid mechanics. If you don't match the Reynolds number then you are talking about completely different flows.
So in short, yes - you need to find data at the same Re number you are modelling. Here is a great resource for low Re airfoils - https://m-selig.ae.illinois.edu/uiuc_lsat.html
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airfoil, ansys, cfx, naca 0012 |
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