Dynamic Wake Identification for Model-and Full-Scale Container Ship

Abstract

Propeller performance prediction is traditionally based on open water calm model basin tests. In waves, and during vessel manoeuvring, inflow to the propeller changes signifi-cantly, i.e. the shape of the wake field will change and propeller load and efficiency are impacted. This paper focus on the changes in wake fraction that can be identified in dynamic conditions. The effects on wake fraction of ship maneuvering and the effects of waves’ orbital velocity are investigated from experimental data. Model basin tests with a free sailing container ship model provide data for identification of propeller load and mean wake fraction during manoeuvring and during passage of waves. The results are verified with analysis during maneuvering in calm sea with a scale model and with the full-scale version of a 45.000 m3 container ship. Experimental results show the wake fraction variation during maneuvering, and estimates of wake fraction derivatives are found with respect to the relative sway velocity at the propeller. The contribution of the paper is to provide evidence for the magnitude of propeller shaft loads that can be expected during passage in a seaway and during manoeuvring.