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Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Id appreciate some help and advising on this really useful PDF.
]1353043533_2431_ft145838_duct_pdf.pdf[/file] specifically my goal is to make a duct with a inner NACA airfoil shape.
But:
-- what is the "advance ratio" (J) ? -- which profile is best for high effciency? (power vs thrust) [it seems NACA 4312 is best at less than 0.2 J] -- im planning to use a special hotwire cutter to make the curve.
Im not wanting others to do my homework, but its all a blur at this point...
EDIT: i see in the Nomenclature section that "J" = U/nD... is this the posistion of the prop fore or aft of a position on an axis?
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
"In aeronautics and marine hydrodynamics, the advance ratio at which a propeller is operating is the ratio between the distance the propeller moves forward through the fluid during one revolution, and the diameter of the propeller. When a propeller-driven vehicle is moving at high speed relative to the fluid the advance ratio of its propeller(s) is a high number; and when it is moving at low speed the advance ratio is a low number. The advance ratio of a propeller is analogous to the angle of attack of an airfoil."
It looks like it's the ratio between pitch and diameter, but it doesn't say whether it is 'theoretical pitch' or 'actual pitch after slip'.
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I need help understanding this PDF doc...
