Benefits from retrofitting a new bulbous bow

The challenges for today’s shipowners are both regulatory and financial. The regulatory matters are difficult to affect, but financial matters can be addressed.

The problem – Every ship traveling through the water creates a bow wave. Creating this wave takes a lot of energy. A sphere moving just underwater creates its own wave, followed by a trough. If you position the sphere just in front of the bow of the ship in the form of a “bulb,” it is possible to align the trough created by the moving sphere with the crest of the bow wave, effectively canceling each other out.

The problem is that the position of the waves created by the bulb and the hull only align under a certain range of speeds and drafts. Slow down or speed up too much and the waves no longer cancel out. In the worst case, the waves become additive and can increase resistance and fuel costs.

The solution – Optimising the Bulbous bow can reduce the wave-making resistance. A retrofitted bulbous bow can reduce fuel consumption from 12% to 15% and reduce CO2 emissions.

The need to change (retrofit) the bulbous bow of the ships is applied when in the process of operation it is established that the actual conditions of use of the ship differ under the conditions for which the bull was optimized at the initial design. There are two main characteristics that determine this discrepancy – the operating draft and the operating speed. The severity of each of these characteristics varies depending on the type of ship.

The engineers from IHB ShipDesign can support you in providing the best solution for using the advantages of this energy-saving retrofit.

In the initial analysis of the retrofit of a bulb, we try to reduce the volume of change of the construction to a possible minimum. The possibilities are:

•  change only part of the bulb (shortening, reducing the height, etc.)
• replacement of the whole bulb
• replacement of the bulb and large parts of the adjacent section

Depending on the requirements set by the client, an analysis is performed and the optimal option is selected, determined by:

• preliminary calculations for the hydrodynamic effect of the change in nose shape for the new operating speed or draft
• the manufacturability of the practical implementation, in accordance with the existing hull construction.
• the impact and compatibility of the change
• multi-objective bulbous bow optimization by means of CFD
• 3D model of the selected bulbous bow for production
• assistance in stability and strength calculations of the new shape for Class requirements

For more details or information – please contact us at office@ihbshipdesign.com.