The great challenge of propeller cavitation in Shipbuilding. Continuous control with the innovative Non-Intrusive Cavitation Detection System (Ni-CDS)

The pressure coefficient depends on the angle of incidence of the flow in the profile.

Cavitation can be reduced under normal operating conditions through good design, such as optimizing propeller loading, ensuring as even water flow across the propellers as possible (which can be affected by hull design), and a careful selection of the characteristics of the propeller, such as: diameter, blade number, pitch, skew and sections.
It is well known that design principles to reduce cavitation (ie, reduce pitch at blade tips) can cause decreased efficiency. The basic function of the propeller is to propel the ship by transforming the power: torque/revolution generated in the main propulsion engines into thrust in the proper direction and direction.

Introduction (IV
To achieve this effect, the propellers, when rotating due to the effect of the engine torque, produce a pressure front on the faces of their blades. While on the back side (pressure side) there is a rise in pressure, on the opposite side, the front side (suction side), there is a remarkable drop in pressure.
The pressure coefficient depends on the angle of incidence of the flow in the profile.

Cavitation. Cavitation Conditions
Being p v the vapor pressure of water at a given temperature, the cavitation number is defined as the relation:

 = −
The cavitation phenomenon occurs when the local pressure p 1 at a point in the fluid is below the vapor pressure p v at that temperature. In a propeller blade profile, high local velocities can occur giving rise to low pressures that, in some cases, can reach the vapor pressure corresponding to the temperature of the water. If this happens, the water vaporizes, forming steam bubbles that are carried away by the flow.

No Cavitación
The process is reversed when reaching higher pressure zones and the bubbles collapse when they change phase again. As the vapor has a much greater specific volume than the liquid phase, an empty zone is produced that is filled with water again. In this process of collapse, high speed pressure waves are generated, resulting in noise, vibrations and deterioration of the blades.  ❖ Increased on the underwater radiated noise by the ship and deterioration and reduction of "stealth".

Cavitation. Cavitation & Noise
The noise and vibrations generated in the ship by cavitation have the following characteristics: For a given design, the control of propeller cavitation includes, among others, the following aspects: When does cavitation start?

How intensely does it occur?
Under what operating conditions does it take place?
What are the parameters that allow its identification? ❖With the ability to collect data from all possible navigation situations ❖ Know when and how the ship's propellers cavitate, in order to adapt to the limitations established in those navigation areas where it is necessary. In this way it will be achieved: ❖Easy installation, with zero impact on the availability of the ship.
❖ Without modifications to the hull or its structure. ▪ Accurate control of cavitation intensity, allowing navigation in noise restricted areas.
▪ Reduction of on board vibration level.
▪ Reduction of the underwater radiated noise signature.
▪ Optimization of the vessel performance in terms of emissions of and fuel consumption.
▪ Detection of undesirable operating conditions. ▪ Non-intrusive installation.
▪ Control of "silent modes" for Military sub-surface ships and submarines.