Abstract
The manoeuvreability of a ship is poor at low speed, but it can be improved considerably by installing a bow thruster.
The model tests which KMW have carried out at HyA show that the thrust from the bow thruster jet does not change with speed. However, the pressure distribution on the hull is changed by the jet so that the resulting side force and turning moment vary with the ship speed. For a 60,000 TDW tanker with a 1500 HP bow thruster the turning moment decreases to 50% at 4 knots and increases again for higher speeds. At 15 knots the moment reaches the zero speed value. For a ship with both bow thruster and rudder, the manoeuvreability is considerably higher than for a ship with rudder only, especially at low speeds (up to 8–10 knots). At 8 knots, for instance, the turning moment for bow thruster and rudder is, 28% higher than for rudder only.
Zig-zag tests both ahead and astern should be carried out on the trial trips so that the bow thruster effciency can be investigated.
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