The discussion confirms that flow over a wing with Reynolds numbers between 350,000 and 1,500,000 is turbulent, as it exceeds the critical threshold of 4,000. While the critical Reynolds number can vary based on flow type, for external flows such as those over wings, turbulence is expected at these values. The hydraulic radius is relevant for calculating flow characteristics in open systems, differing from pipe flow calculations. Experimental testing is often necessary to determine the exact transition between laminar and turbulent flow on a wing surface.
PREREQUISITESAerospace engineers, fluid dynamics researchers, and students studying aerodynamics will benefit from this discussion, particularly those interested in the behavior of airflow over wing surfaces.
Not really. Hydraulic radius is for channel flow. For external (non-channel) flow, it's true that Re = 4000 is not necessarily the critical reynolds number. Unfortunately, it can be difficult to get the true critical reynolds number without experimentally testing it, but it can be anywhere from a couple thousand up to roughly 1 million. In general, for a wing at Re = 3.5*105 to 1.5*106, I would guess that the flow is turbulent, as it is near the upper end of this range. At the very upper end of this range (Re just under 106), you would probably only get laminar flow on a very smooth plate. Of course, just because turbulent flow exists doesn't mean that it's turbulent over the whole wing. If the wing surface is rough at all, you'd probably get a transition to turbulent flow pretty early on, but if the wing is smooth, a significant portion of the wing would have laminar flow. Again, I'm not sure how to determine exactly how much would be laminar aside from experimentally.random54 said:It's turbulent for any Re > 4000. The calculation of Re number depends on what type of flow it is. For open systems (such the wing is in this case) you have to use hydraulic radius instead of charasterictic length used in pipe flows.
There is a wikipedia article how to calculate certain flows hydraulic radius:
http://en.wikipedia.org/wiki/Hydraulic_radius#Hydraulic_radius