Propulsion performance prediction for towing ship

Abstract

Towing of various objects is a common marine operation. There is a whole group of ships intended for this work, like tugs, fishing vessels, seismic survey ships and industrial vessels. Towing operations of these ships typically proceed at the speeds of 1–4 m/s. The assumptions used to determine pulling performance parameters of towing ships are usually over-simplified. This paper suggests an analytical and experimental method intended to determine pulling performance of propulsion systems for towing ships.Typically, pulling and propulsion performance parameters of ships are obtained through a calculation using the results of towing and self-propulsion model tests. However, this conventional approach is not applicable to pulling performance calculations of towing ships because self-propulsion test results for towing ships at the speeds corresponding to this operation scenario give absurd values for propeller-hull interaction coefficients. The classic system of propeller-hull interaction coefficients does not work for towing ships at low advance ratios.To overcome these difficulties, this paper suggests an alternative system of propeller-hull interaction coefficients that is applicable to towing ships and gives a calculation method of pulling performance calculation for towing ships based on this alternative system, taking Yuribei tugboat as a case study.