Performance Coefficient of a Vessel

(khodkost’ sudna), the ability of a ship to develop a given speed for a given expenditure of power of the main engine or, for a sailing ship, for a specific area of sail. Of two similar ships, the one that develops a higher speed for the same power from the main engine has a better performance coefficient; for sailing ships the coefficient is determined by greater speed for the same area of sail. The performance coefficient is one of the primary characteristics of a ship.

The performance coefficient is affected by the lines of the ship, the type and shape of the ship, the operating regime of the engine, the principal dimensions of the ship and other factors. A theoretical calculation of the performance coefficient does not give reliable practical results, because it is impossible to consider many factors that are difficult to determine. Therefore, in order to ensure that a ship design has the best possible performance coefficient, the results of tests of models, for example, in a test basin, are used in calculations during the design process. After a ship is built, its performance coefficient is determined during trials.