A Bulbous Bow and its importance
One thing that often catches the eye of a common man regarding most of the ships, is the bulb like projection at the forward end of the ship, often below the waterline.There is no doubt in the fact that at some point of your life, you have questioned yourself regarding the reason behind the presence of this structure. Well, since it generally resembles the shape of the bulb, and always placed at the bow of the ship, it is known as a Bulbous Bow.
Let’s look back to about a hundred years from now. Remember Titanic? You must have observed it didn’t have a bulbous bow. But try having a look at the bows of modern cruise ships, container ships, LNG carriers, research vessels, etc. All of them are characterized with a bulbous bow. Not only mono hull ships, today almost even catamarans are equipped with a bulbous bows rather than straight bows. Why?
When a ship surges, it generates its own Kelvin waves (the ones you see around a ship when it sails in open sea) as shown in Figure 1.
Now visualize it this way- the waves are basically travelling forms of energy in water medium. Where did this energy come from? In other words, who energized the water particles to form these waves?
It is the moving mass of the ship that does this job. Note the word “moving”. The ship’s movement is powered by its propulsion system. A part of the energy delivered by the engine goes into rotating the propeller, and in turn, a fraction of that thrust generated by the propeller comes handy in actually propelling the ship. Where does the rest of the energy go? Remember, water particles were energized to transmit waves? That’s your answer. This is also called Wave Making Resistance of a ship.
Now, why are we discussing this, and what does this have to do with a bulbous bow?