Download UNDERVISNING I TPM VED HiB

THE AIR/HYDROFOIL
A BRIEF TECHNICAL INTRODUCTION
AND
HISTORIC OVERVIEW
What is the secret?
WHAT IS AN AIR/HYDROFOIL?
• Any object subject to fluid
flow will experience a
force in the direction of
the flow. This is called
drag.
• An air/hydrofoil is a
device which, correctly
located in a fluid flow,
also will experience a
force normal to the
direction of the incoming
flow. This is called lift.
Practical use of air/hydrofoils
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Sail
Rudder
Wind turbine
Propeller
Hydrofoil (boat)
Airplane wing
Helicopter rotor
In machinery, like pumps, turbines, and
fans
Bernoulli’s equation
• p + 0.5rV2 + rgh = Constant
p = Fluid Pressure [N/m2]
r = Fluid Density [kg/m3]
V = Fluid Velocity [m/s]
g = Gravitational Acceleration Constant [m/s2]
h = Pressure Height or Submergence [m]
Speed Distribution
Streamlines and pressure distribution
How is it
possible to
sail up-wind?
HISTORY – THE HYDROFOIL
• In Devonian time, from about 415 to 355 million
years ago, fishes of many different types were
swimming and hunting in the seas.
HISTORY – THE AIRFOIL
• Nature invented the airfoil
during the Late Cretaceous
period, 105-65 mill years
ago.
• This is the quetzalcoatlus,
one of the pterosaurs from
this period. They were
flying reptiles, with a
maximum wing span of
12 – 15 m.
The first
air/hydrofoils made
by man were the
sail and the rudder.
The Chinese
developed the
stern post rudder
and for-and-aft rig
during the last part
of the Han dynasty,
200 BC – 200 AD.