Answer
Hull optimization means improving the shape, surface condition, and appendages of the hull so that the ship requires less propulsive power for the same speed.
The main principle is:
Lower hull resistance→lower required power→lower fuel consumption
Hull efficiency can be improved by:
- Optimized bow shape / bulbous bow: Reduces wave-making resistance by creating favourable interference between bow waves. It is optimized for the vessel’s actual operating draft and speed.
- Optimized hull form: Proper length-to-beam ratio, block coefficient, entrance angle, stern shape, etc. reduce both viscous resistance and wave resistance.
- Improved stern flow: A well-designed stern gives more uniform water flow into the propeller, reducing flow separation and improving propulsive efficiency.
- Reduced wetted surface / smoother hull: Lower wetted surface area and a smooth fair hull reduce skin-friction resistance.
- Low-friction / antifouling coatings: Prevent marine growth and reduce hull roughness. Fouling can significantly increase resistance and fuel consumption.
- Appendage optimization: Properly designed rudder, shaft brackets, bilge keels, sea-chest openings, etc. reduce appendage and turbulence losses.
- Energy-saving devices: Devices such as pre-swirl stators, ducts, fins and optimized rudders improve the flow reaching or leaving the propeller and recover rotational energy.
- Air lubrication systems: A layer of air bubbles beneath the hull can reduce frictional resistance on suitable vessels.
- Trim and draft optimization: Operating at the optimum trim reduces resistance at the actual speed and loading condition.