Normal Oil Flow Images from Unmodified Wings

(click to enlarge images)

Typical Top Surface Oil Flow Typical Bottom Surface Oil Flow
Top surface showing the four classic regions:
1. attached laminar flow (near leading edge)
2. detached laminar flow (ahead of bubble)
3. transition bubble flow (band of oil)
4. attached turbulent flow (aft of bubble)
Bottom surface showing transition bubble. The narrow (turbulator) tape behind (left of) the
bubble has dimples designed to trip the flow from laminar to turbulent. It should be located
ahead of the bubble about where the oil begins. It's purpose is to transition from laminar to
turbulent flow without a bubble, thereby making the wing appear thinner to the free stream

Typical Top Surface Oil Flow Near Wing Tip
The four classic flow regions near the wing tip. The transition bubble is very distinct. The angled flow near the tip is from the vortex resulting from the lower pressure on the top side of the wing compared to the higher pressure beneath. It illustrates the reason winglets have a toe out angle.

Typical Bottom Surface Oil Flow Near Wing Tip
The bottom surface transition bubble is less distinct than the top surface. In three places, the bubble is tunnelled through by turbulent attached flow initiated by imperfections ahead of the bubble. Leading edge bug strikes have this effect, resulting in an attached turbulent wake that widens as the flow crosses the wing.

Jim Hendrix
Oxford Aero Equipment

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