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Old 12-12-2013, 05:17 PM   #9 (permalink)
aerohead
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water

Quote:
Originally Posted by jesdreamer View Post
The Box Cavity photo shows what I referred to as a recessed back KammBack configuration. And I realize that Renold's Number is involved -- but it has been many many years since my college fluid dynamics course and I need some help in learning whether a recessed KammBack would help reduce drag in a fluid denser than air (such as water) -- I am considering airfoil (hydrofoil) structures and plan to truncate as per the info posted above but would like to explore some calculations and am lost in the math. I don't have a clue as to how to mathematically treat or explore effect on drag (if any) as related to the recess distance back behind the outer projecting edge -- For that matter,
will the drag reduction of truncating downstream end of an airfoil (hydrofoil) in water have proportionally a similar effect as per info above for air as the fluid??
*3/8 th-scale automobile models have been tested underwater both by Ford and Mercedes-Benz.
*Water is 833X more dense than air and for proper Reynolds number 2-mph towing speed will represent 30-mph in air at full-scale,which gets your Rn above critical for turbulent boundary layer.
*As to the mathematics,model scale testing has been preferred to CFD in some instances do the the complex nature of the 3D flow.
*Kamm and his son tested cars underwater at the Stephens Institute at Hoboken,New Jersey.
*The David Taylor Model Basin,Maryland,operated by the US NAVY is the most famous of these laboratories.Some of the human-powered submarine competitions take place in their facility.
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