Post by email@example.com Post by Carl Fink Post by firstname.lastname@example.org
Airfoil (or aerofoil) and hydrofoil are devices to produce lift in
air or water, respectively. I have seen both "foil" and "fluid foil"
used for the general case of a device used to produce lift in
a flow of fluid.
I prefer fluid foil, as this immediately shows that you are dealing
with fluid flows, and not fencing swords, thin and flexible sheets
of metal or fictional characters. I am interested in any comments
or preferences on the use of either of these terms. Also, are there
other terms with the same meaning in use in science or industry?
The phrase "fluid foil" does not occur in standard English. Is this some
specific technical dialect you're planning to use? If it is remotely
possible to confuse the thing you're talking about with a fencing foil, I
would avoid using the word "foil" at all and just refer to a lifting
surface or something.
I found several uses of "fluid foil". This is from an article titled
_The Fluid Foil: the Seventh Simple Machine_, by Charles R. Mitts, in the
A simple machine does one of two things: create a mechanical advantage
(lever) or change the direction of an applied force (pulley). We know
the current list of six simple machines and can provide examples of each,
but what about examples such as: kites, sails, fan blades, wings, airplane
propellers, marine propellers, and gas and hydro turbine blades? Where do
these fit in? These can be referred to as "fluid foils" Fluid foils are
unique among simple machines because they not only change the direction of
an applied force (wheel and axle); they convert fluid energy into mechanical
energy (wind and Kaplan turbines) or vice versa, mechanical energy into
fluid energy (fans and propellers).
My thanks to all who replied. I have decided to use the term fluid foil,
with a sentence or two to introduce and define it as Charles Mitts does
in the article I've quoted.
The term "airfoil" was only introduced in 1919. I have found the use
of "fluid foil" as far back as a 1934 United States patent, granted
to aeronautical engineer David Davis (1894-1972), a co-founder of
Douglas Aircraft and perhaps best known today for the Davis wing
used on the World War 2 B-24 bomber:
"This invention relates to a construction of foils to be driven through a
fluid, and particularly concerns the profile of the foil in its front to rear
section. While the invention may be applied to a foil used in any medium, it
has its greatest usefulness when applied in the construction of airfoils for
The upper surface of a fluid foil should have a profile, which, when the foil
is driven through the fluid, will develop a region of reduced pressure on the
upper side of the foil, and the underside of the foil should have a profile
that will develop increased pressure on the underside of the foil. These
differential pressures result in a force which can be resolved into a lift
component perpendicular to the direction of movement and a drag component
parallel to the direction of movement."