Kongsberg Simrad CP200-5C, Installation Manual

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Flow noise
Consider the situations when the vessel is unloaded, and pitching in heavy seas. The vessel
is riding high, and the bow may even be lifted out of the water. This will cause a lot of
air to follow the shape of the hull.
The upper water layers of the sea contain a myriad of small air bubbles created by the
breaking waves. In heavy seas the upper 5 to 10 metres may be filled with air, and the
highest concentrations will be near the surface. Air bubbles absorb and reflect the sound
energy, and they may in worst cases block the sound transmission altogether.
Cavitation
Cavitation is the formation of small air bubbles close to the transducer face. The bubbles
appear because the local pressure becomes negative during parts of the acoustic pressure
cycles. The cavitation threshold increases with the hydrostatic pressure. The noise is made
when the bubbles implode.
Transmitting in air
The transducer must never be lifted free of the water surface. If the transducer is activated
when out of the water it may be damaged beyond repair. Mounting the transducer at a deep
position on the hull will normally prevent this.
Slamming
Slamming happens if the vessel hull climbs out of the water in heavy seas. The force of the
water when the hull falls down can push the transducer up, and this may cause damage
both to the transducer and to its mounting. This is especially important for low frequency
transducers with large faces. The effect of slamming can be reduced by mounting the
transducer as deep as possible on the hull.
Note
Kongsberg Maritime AS takes no responsibility for any damages to the transducer, the cable
or the mounting arrangement, caused by slamming.
Related topics
Preparations, page 22
Where to install the transducer, page 38
Preparations