Simrad ES120-7C - REV D, Руководство по установке, Страница: 75 / 98

330254/B
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• The turbulent flow is a disorderly flow pattern, full of eddies.
A Turbulent flow
B Laminar flow
C Air bubbles
Air bubbles absorb and reflect the sound energy, and they may in worst cases block the
sound transmission altogether.
The boundary layer increases in thickness when it becomes turbulent. The boundary layer
is thin in the forward part of the vessel hull, and increases as it moves aft. The thickness
depends on ships speed and on the roughness of the hull. All objects sticking out from
the hull, or dents in the hull, will disturb the flow and will increase the thickness of the
boundary layer. When the flow speed is high, the turbulence can be violent enough to
destroy the integrity of the water. Small voids or cavities in the water will occur and this
is called cavitation.
It is our experience that a wide and flat bottom, with a rising angle less than around 13
degrees, is prone to giving air problems for the transducer. In any case a transducer location
in the forward part of the hull is preferred in order to minimise the influence of the boundary
layer.
Keep the transducer far away from the
propellers
The propulsion propellers is the dominant noise source on most vessels. The noise is
easily transmitted through the water. This noise may often reduce the overall performance
of your ES120-7C.
The transducer must be installed as far away from the propellers as possible. The best
positions are therefore on the fore part of the hull. Positions outside the direct line of sight
from the propellers are best.
Where to install the transducer