Figure 6 shows the increase of the pressure fluctuation when the cavitation is generated over the propeller, in comparison with the propeller sustaining no cavitation phenomenon. The example on the left hand is for tanker, and that on the right hand is for container ship. You will see that in either case, when cavitation is not generated, water pressure fluctuation is smoothly increased in accordance with the propeller shaft speed increased, however, once the cavitation is generated, the situation will abruptly be different. When the cavitation is generated, the water pressure fluctuation will rapidly be increased, which will be a cause for the serious hull vibration. From the viewpoint of the comfortableness to be improved, the less the cavitation is generated, the better the hull condition will be.
With the recent vessels from which high speed and high efficiency are expected, it will be impossible for the cavitation to thoroughly be eliminated. In that sense, efforts were made for devising the reduction of cavitation phenomenon, even if it cannot be avoided. One of the devices successfully realized for practical use is highly skewed propeller.
