Supercavitating propeller
Encyclopedia
The supercavitating propeller is a variant of a propeller
for propulsion in water, where supercavitation
is actively employed to gain increased speed by reducing friction. They are being used for military purposes and for high performance boat racing
vessels as well as model boat racing.
This article distinguishes a supercavitating propeller from a subcavitating propeller running under supercavitating conditions. In general, subcavitating propellers become less efficient when they are running under supercavitating conditions.
The supercavitating propeller operates submerged with the entire diameter of the blade below the water line. Its blades are wedge-shaped to force cavitation at the leading edge and to avoid water skin friction along the whole forward face. As the cavity collapses well behind the blade, the supercavitating propeller avoids the spalling damage due to cavitation that is a problem with conventional propellers.
An alternative to the supercavitating propeller is the surface piercing
, or ventilated propeller. These propellers are designed to intentionally cleave the water and entrain
atmospheric air to fill the void, which means that the resulting gas layer surrounding the propeller blade consists of air instead of water vapour. Less energy is thus used, and the surface-piercing propeller generally enjoys lower drag than the supercavitating principle. The surface-piercing propeller also has wedge-shaped blades, and propellers may be designed that can operate in both supercavitating and surface-piercing mode.
Supercavitating propellers were developed to usefulness for very fast military vessels by Vosper & Company
The pioneer of this technology and other high speed offshore boating technologies was Albert Hickman
(1877–1957), early in the 20th century. His Sea Sled
designs used a surface piercing propeller.
Propeller
A propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and a fluid is accelerated behind the blade. Propeller dynamics can be modeled by both Bernoulli's...
for propulsion in water, where supercavitation
Supercavitation
Supercavitation is the use of cavitation effects to create a bubble of gas inside a liquid large enough to encompass an object traveling through the liquid, greatly reducing the skin friction drag on the object and enabling achievement of very high speeds...
is actively employed to gain increased speed by reducing friction. They are being used for military purposes and for high performance boat racing
Boat racing
-Types:* Canoe racing, competitive forms of canoeing and kayaking* Drag boat racing, a form of drag racing which takes place on water rather than land* Dragon boat racing, a type of human-powered watercraft racing...
vessels as well as model boat racing.
This article distinguishes a supercavitating propeller from a subcavitating propeller running under supercavitating conditions. In general, subcavitating propellers become less efficient when they are running under supercavitating conditions.
The supercavitating propeller operates submerged with the entire diameter of the blade below the water line. Its blades are wedge-shaped to force cavitation at the leading edge and to avoid water skin friction along the whole forward face. As the cavity collapses well behind the blade, the supercavitating propeller avoids the spalling damage due to cavitation that is a problem with conventional propellers.
An alternative to the supercavitating propeller is the surface piercing
Surface piercing propeller
The surface piercing or ventilated propeller is a propeller that is designed to intentionally cleave the water and entrain atmospheric air to fill the void, which means that the resulting gas layer surrounding the propeller blade consists of air instead of water vapour...
, or ventilated propeller. These propellers are designed to intentionally cleave the water and entrain
Entrainment (engineering)
Entrainment as commonly used in various branches of engineering may be defined as the entrapment of one substance by another substance. For example:* The entrapment of liquid droplets or solid particulates in a flowing gas, as with smoke....
atmospheric air to fill the void, which means that the resulting gas layer surrounding the propeller blade consists of air instead of water vapour. Less energy is thus used, and the surface-piercing propeller generally enjoys lower drag than the supercavitating principle. The surface-piercing propeller also has wedge-shaped blades, and propellers may be designed that can operate in both supercavitating and surface-piercing mode.
Supercavitating propellers were developed to usefulness for very fast military vessels by Vosper & Company
Vosper & Company
Vosper & Company, often referred to simply as Vospers, was a British shipbuilding company based in Portsmouth, England.-History:The Company was established in 1871 by Herbert Edward Vosper, concentrating on ship repair and refitting work....
The pioneer of this technology and other high speed offshore boating technologies was Albert Hickman
W. Albert Hickman
William Albert Hickman was a Canadian designer and manufacturer of innovative fast boats. He is best known as the inventor of the Hickman Sea Sled....
(1877–1957), early in the 20th century. His Sea Sled
Hickman sea sled
The Hickman Sea Sled is an inverted vee planing hull invented by Albert Hickman. The Sea Sled is a direct forefather of the modern high speed catamaran or tunnel hull....
designs used a surface piercing propeller.