Abstract

The recently issued IMO requirements for reduction of GHG emissions for shipping reinforced the attempts to increase the energy efficiency of ships.

One of the measures prescribed by IMO is Ship Energy Efficiency Management Plan (SEEMP). This, among other things, involves trim optimization.

Trim i.e. difference between the draft at the bow and the stern is controlled parameter worthy of attention with respect of fuel usage and GHG emissions while the ship is cruising. It is shown in this paper that the powering performance of vessels varies with different trim conditions.

The main objective function of the trim optimization is the powering performance (resistance and propulsion).

The objective of this paper is to analyze the physics behind the effect of varied trim on ship resistance and propulsion, to detect the origin of this effect.

In particular are examined the change of total resistance depending on the change of some parameters such as length of waterline (hence frictional resistance), submerged surface , change of the residual resistance, wave making/breaking at the bow and analyzed in terms of and viscous – pressure resistance (form-factor). Also examined are parameters influencing the powering performance as: thrust deduction, wake fraction, relative rotative efficiency, and propeller efficiency when the ship is trimmed.
This analysis has been based on experimental data of particular ships.