Oil Drop Flow Test on the Cowl
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I wanted to show some pictures of the oil drop flow test I did on the cowl. You will notice almost no air movement on the flat surface near the prop extension. Some could argue that the flat area on my cowl prevents air movement, but I would think the prop would cause some rotation of air. It doesn't happen.
I wonder if the air at the lip of a normal cowl reverses direction, restricting the outlet of a normal cowl opening. I have exceptional cooling, and the outlet area is very restricted with exhaust pipe in the center of the eductor. It might be possible I am getting an augmentation effect. It would interesting to measure the pressure in this area of a standard design.... any takers?
Here is Terry Schuber's analysis of the pictures:
Terry has been a leading developer on drag reduction and I value his opinion and guidance this such esoteric subjects as tea leave reading, astrology, and oil flow insight. THANKS Terry for you wisdom.... :-)
Fuselage Sides, Notice the separation just aft of the fuel sump.
Gear legs, notice the separation just aft of the gear leg fairs because I do not have
a clean transition from the gear leg to the fuselage.
Oil cooler inlet.
Bottom Cowl area, notice the little air movement near the prop extension and the separation where the cowl clears the starter ring gear.
On the aft end of the cowl just above the eductor the oil lines are nice and straight. Right next to the eductor outlet, the oil flow lines just dribble down the cowl showing the extent of the air separation.