High performance hull form
Optimum hull form for medium-speed ships enabling energy saving and operation time saving
SEA-Arrow (Sharp Entrance Angle bow as an Arrow)
"SEA-Arrow" (patented) is a newly developed optimum shape of bow for medium-speed ships such as LPG carriers. It can significantly reduce the bow wave resistance and enhances the ship's propulsive performance. Furthermore, it can realize a drastic reduction in the fuel consumption and shortening of shipping schedules.
LPG carriers are required to have box-shape tanks arranged forward of the bow for the purpose of efficient arrangement of LPG tanks, and also required to develop a higher ship speed than oil tankers and bulk carriers. Their lengths are restricted due to the facilities of their loading/unloading ports.
Under these restrictions in design, the conventional stem LPG carriers are designed to be relatively full in the bow part, which generates high waves around the bow. These bow waves produce large hull resistance.
In such circumstances, we have carried out R & D of LPG carriers' hull form, aiming at higher propulsive performance by minimizing the bow waves, and developed SEA-Arrow having no protrusion of bulb, keeping the effect of bulbous bow.
The features of SEA-Arrow are as follows:
LPG carriers are required to have box-shape tanks arranged forward of the bow for the purpose of efficient arrangement of LPG tanks, and also required to develop a higher ship speed than oil tankers and bulk carriers. Their lengths are restricted due to the facilities of their loading/unloading ports.
Under these restrictions in design, the conventional stem LPG carriers are designed to be relatively full in the bow part, which generates high waves around the bow. These bow waves produce large hull resistance.
In such circumstances, we have carried out R & D of LPG carriers' hull form, aiming at higher propulsive performance by minimizing the bow waves, and developed SEA-Arrow having no protrusion of bulb, keeping the effect of bulbous bow.
The features of SEA-Arrow are as follows:
- The bow wave resistance can be reduced to half, compared with the conventional stem LPG carriers.
- The required main engine horsepower can be decreased by 6% to 10% from the conventional LPG carriers at the same ship speed.
- The ship speed can be increased by 0.3 to 0.5 knot from the conventional LPG carriers at the same main engine horsepower.
SEA-Arrow has already been applied to ten LPG carriers. Analyzing their voyage data, we have confirmed their high propulsive performance in loaded condition.
Comparison of bow waves at model tank test
Kawasaki SEW (Stern End Wedge)
"Kawasaki SEW" (patented) has a characteristic stern profile having an inflection point near the stern end of the ship. It reduces stern waves and is effective for high speed ships such as container ships and pure car carriers.
The conventional high speed ships generate large stern waves from their stern end. The Kawasaki SEW has a downward stern profile to the stern end from the inflection point. The flows through Kawasaki SEW are accelerated and the accelerated flow field is capable of restraining the wave breaking and the wave height at the stern. As a result, Kawasaki SEW reduces stern wave resistance and required propulsive power by 3% to 7%.
Kawasaki SEW has already been installed on ten high speed ships.
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