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Boundary layer thickness of cylinder

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Old   March 4, 2019, 16:28
Default Boundary layer thickness of cylinder
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Joanna Pazdur
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Hi,

I am simulating air flow past cylinder and I wanted to calculate analytically the boundary layer thickness, just to compare it with what I got from Fluent. So I found this formula: δ ≈ 4,91√(νx/u) but I read it is applicable for flat plates. So my question is: can I apply this formula to a cylinder? And if yes, then my second question is: does x in the formula refer to the distance along the surface of the cylinder ex. half the circumference or rather the distance "across" the cylinder (I mean straight in the direction of the flow) ex. diameter?

I would be very grateful for any reply!
Regards,
Asia
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Old   March 4, 2019, 16:43
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Filippo Maria Denaro
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No, you cannot use the BL theory over a flat plate
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Old   March 4, 2019, 16:58
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You meant I cannot apply it to the cylinder, didn't you? Cuz you wrote "flat plate" and my question is about cylinder.
Anyway, thanks for reply!
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Old   March 4, 2019, 17:04
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Quote:
Originally Posted by Asiap View Post
You meant I cannot apply it to the cylinder, didn't you? Cuz you wrote "flat plate" and my question is about cylinder.
Anyway, thanks for reply!

yes, you can't use the theory valid for the semi-infinite flate plat for the case of a flow over a cylinder
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Old   March 4, 2019, 17:11
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Is there any formula for the boundary layer thickness in the case of a cylinder then?
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Old   March 4, 2019, 22:52
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Do a search for Thwaites method.
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