Estimation of a ship’s nominal wake fraction through full-scale speed trials

A ship’s nominal wake fraction is a key parameter in the design of the marine propulsion system, i.e. the the marine propulsor and main engine. Determination of the wake fraction is commonly done through empirical formulas and / or based on model-scale experiments. However, a discrepancy exists between the model- and full-scale estimation results because of the way scaling is applied. Speed trials are conducted to estimate the full-scale nominal wake fraction. Results show the ability of the developed speed-trial methodology to provide an initial estimation of the full-scale nominal wake. However, comparison between the empirical, model-scale, and full-scale results fails to provide conclusive results. No real insight into the validity of the estimated full-scale nominal wake fraction could be established. However, the applied methodology is deemed to have value but additional research is required before further conclusions can be drawn.