3. Objective
1) To understand the constructional
features of bulbous bow.
2) Operational requirement for
incorporating bulbous bow on ships.
4. Background
• Mr. Froude’s experiment
• Russian sciencetist Mr. VLADIMIR
• SS Normandie
• Mr. TAKAO INUI
5. 1) A bulbous bow is an extension of the
hull just below the load waterline
2) The basic purpose is to create a low-
pressure zone to reduce or eliminate
the bow wave and reduce the
resulting drag
6. Working Principle
• The wave system generated by the bulb interferes
with the kelvin wave system of the ship.
• The length of the bulb defines the phase of
interference and its volume determines the width of
its wave system.
• Destructive interference of waves.
7. 1) Generally at low speeds the effect
of the bulb is negative. When the
Froude Number (FN) increases, its
effect becomes positive and
increases up to a maximum value.
2) Until now, a bulbous bow has been
often designed using Kracht charts,
which were established based on
model test data, but these charts
apply only to ships with a block
coefficient CB = 0.56-0.82, Froude
number Fn = 0.20-0.40, and the
8.
9.
10. Advantages of bulbous bow
• Reduces bow generated waves.
• Act as a robust bumper in event of collision
• It reduces pitching to a small extent
• Allows installation of bow thrusters to maximum fwd of ship’s
length
• Act as reserve buoyancy at forward of ship or reserve for
floatation
• It increases the ship’s water line length, slightly increasing ships
speed
• Decreases fuel consumption by 10 to 15 percent.
• Typical use in ice breaking ships.
