Search results
Results from the WOW.Com Content Network
In order to reduce the possibility of cavitation happening in marine propellers, a set of nozzles are placed on the hull of the ship directly in front of the propeller. These nozzles spray out compressed air over the propeller that creates "a macro bubble". [1] This bubble completely encompasses the propeller that is in operation.
Cavitation is usually an undesirable occurrence. In devices such as propellers and pumps, cavitation causes a great deal of noise, damage to components, vibrations, and a loss of efficiency. Noise caused by cavitation can be particularly undesirable in naval vessels where such noise may render them more easily detectable by passive sonar.
If the reduction in pressure is too much in relation to the ambient pressure of the fluid, cavitation occurs, bubbles form in the low pressure area and are moved towards the blade's trailing edge where they collapse as the pressure increases, this reduces propeller efficiency and increases noise. The forces generated by the bubble collapse can ...
A toroidal propeller is a type of propeller that is ring-shaped with each blade forming a closed loop. The propellers are significantly quieter at audible frequency ranges, between 20 Hz and 20 kHz, while generating comparable thrust to traditional propellers. In practice, toroidal propellers reduce noise pollution in both aviation and maritime ...
The goals of the Ship Silencing Program are a reduction of sonar self noise over the frequency range of passive capable sonar and the reduction in the ship's radiated noise to reduce detection by enemy submarines. [citation needed] Self-noise is the noise generated by a ship that has an effect on its own sonar and sensors. Radiated noise is the ...
Machinery noise: noise generated by a ship's engines, propeller shafts, fuel pumps, air conditioning systems, etc. Cavitation noise: noise generated by the creation of gas bubbles by the turning of a ship's propellers. Hydrodynamic noise: noise generated by the movement of water displaced by the hull of a moving vessel.
Silent running is a stealth mode of operation for naval submarines.The aim is to evade discovery by passive sonar by eliminating superfluous noise: nonessential systems are shut down, the crew is urged to rest and refrain from making any unnecessary sound, and speed is greatly reduced to minimize propeller noise.
A ducted propeller, also known as a Kort nozzle, is a marine propeller fitted with a non-rotating nozzle. It is used to improve the efficiency of the propeller and is especially used on heavily loaded propellers or propellers with limited diameter. It was developed first by Luigi Stipa (1931) and later by Ludwig Kort (1934). The Kort nozzle is ...