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A pump-jet, hydrojet, or water jet is a marine system that produces a jet of water for propulsion. The mechanical arrangement may be a ducted propeller ( axial-flow pump ), a centrifugal pump , or a mixed flow pump which is a combination of both centrifugal and axial designs.
Even though these fluctuations in drag and mass can be ignored if the frequency of the jet-propulsion cycles is high enough, jet-propulsion is a relatively inefficient method of aquatic locomotion. All cephalopods can move by jet propulsion, but this is a very energy-consuming way to travel compared to the tail propulsion used by fish. [13]
Jet propulsion is produced by some reaction engines or animals when thrust is generated by a fast moving jet of fluid in accordance with Newton's laws of motion.It is most effective when the Reynolds number is high—that is, the object being propelled is relatively large and passing through a low-viscosity medium.
Squid giant axon. The squid giant axon is the very large (up to 1.5 mm in diameter; typically around 0.5 mm) axon that controls part of the water jet propulsion system in squid.
Water jets are best suited to fast vessels and are thus used often by the military. Water jet propulsion has many advantages over other forms of marine propulsion, such as stern drives , outboard motors , shafted propellers and surface drives .
A waterjet thruster is a special type of bow thruster that utilizes a pumping device instead of a conventional propeller. The water is discharged through specially designed nozzles which increase the velocity of the exiting jet. Waterjets generally have the advantage of smaller hull penetrations for an equivalent size thruster.
Water jet may refer to: A jet of water under pressure, like in an ornamental fountain or drain cleaner; Pump-jet, a marine propulsion mechanism for jetskis and other types of boats; Water jet cutter, a tool for cutting and the machining of engineering materials; Water-jet printer, a printer that makes use of water instead of ink; Dental water ...
A water jet, or pump-jet, is a marine propulsion system that uses a jet of water. The mechanical arrangement may be a ducted propeller with nozzle, or a centrifugal compressor and nozzle. The pump-jet must be driven by a separate engine such as a Diesel or gas turbine. A pump jet schematic.