Water Jet Propulsion-Operational Experience from Large Installations

Abstract

To make a power prediction for a propeller driven vessel the hull resistance is usually first determined by separate tests. After that the thrust deduction, wake fraction and relative rotative efficiency are determined in self propulsion tests. After scale effects have been taken into consideration also the model basin's statistical correlation factors are usually put on top of that to predict the required power and shaft speed for the full scale vessel. Theoretically the same procedure could be used for water jet propelled craft. However the measurements involved in the self propulsion tests with water jets, like flow rate measurements must be extremely accurate to give a reliable end result. Further scale effects are more difficult to predict. By extensive testing in the Kamewa' s cavitation tunnels as well as in full scale Kamewa has developed software that very accurately predicts full scale flow rates and shaft speed for given shaft power and ship speed.