1 General
Clasification Society 2024 - Version 9.40
Statutory Documents - IMO Publications and Documents - Circulars - Marine Environment Protection Committee - MEPC.1/Circular.796 – Interim Guidelines for the Calculation of the Coefficient fW for Decrease in Ship Speed in a Representative Sea Condition for Trial Use – (12 October 2012) - Annex – Interim Guidelines for the Calculation of the Coefficient fW for Decrease in Ship Speed in a Representative Sea Condition for Trial Use - Part 1: Guidelines for the Simulation for the Coefficient FW for Decrease in Ship Speed in a Representative Sea Condition - 1 General

1 General

1.1 Application

1.1.1 The purpose of these guidelines is to provide guidance on conducting the simulation to obtain the coefficient f w for an individual ship, which is contained in the EEDI.

1.1.2 These guidelines apply to ships of which ship resistance as well as brake power in a calm sea condition (no wind and no waves) is evaluated by tank tests, which mean model towing tests, model self-propulsion tests and model propeller open water tests. Numerical calculations may be accepted as equivalent to model propeller open water tests or used to complement the tank tests conducted (e.g. to evaluate the effect of additional hull features such as fins, etc., on ship's performance), with approval of the verifier for the EEDI.

1.1.3 The design parameters and the assumed conditions in the simulation to obtain the coefficient f w should be consistent with those used in calculating the other components in the EEDI.

1.1.4 f w may also be determined by the verifier's acceptance of the tank test and/or simulated data from the ship of the same type's performance in representative sea condition.

1.2 Method of calculation

1.2.1 Symbols

  • PB : Brake power
  • RT : Total resistance in a calm sea condition (no wind and no waves)
  • Vref : Design ship speed when the ship is in operation in a calm sea condition (no wind and no waves)
  • Vw : Design ship speed when the ship is in operation under the representative sea condition
  • ΔRwave : Added resistance due to waves
  • ΔRwind : Added resistance due to wind
  • ηD : Propulsion efficiency
  • ηS : Transmission efficiency
  • Subscript w refers to wind and wave sea conditions.

1.2.2 The basic procedures in calculating decrease in ship speed is shown in figure 1.1. (See section 4 for more information.)

Figure 1.1 Flow chart of calculation for the decrease in ship speed

1.2.3 Relation between the power and the decrease of ship speed is shown in figure 1.2

Figure 1.2 Relation between power and the decrease in ship speed

Parent topic: Part 1: Guidelines for the Simulation for the Coefficient F W for Decrease in Ship Speed in a Representative Sea Condition
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