Analysis of the thrust deduction in waterjet propulsion – The Froude number dependence
Journal article, 2018

The definition of thrust deduction in waterjet propulsion is different from that of a propeller driven hull and cannot be interpreted in the same way. A particularly interesting feature of the waterjet thrust deduction is the large variation with Froude number. This is well known from experience, but has never been fully explained. The objective of this paper is to use CFD to address the reasons for these large variations. To this end, the thrust deduction fraction is split into resistance increment fraction and jet thrust deduction fraction. The former is due to the self-propelled hull resistance change in comparison with the bare hull resistance and the latter is due to the difference between gross and net thrust. This split reveals that the main reason for the thrust deduction variation is the hull resistance change. Analysis of the resistance increment in different speed ranges is performed by studying the hydrostatic and hydrodynamic pressure changes on the hull as well as the friction change due to the waterjet system. Despite the negative thrust deduction fraction in the intermediate speed range there is no indication of a resistance reduction compared to that of the bare hull at these speeds.

Thrust deduction

Net thrust

Gross thrust

Sinkage and trim

Waterjet propulsion

Resistance

Author

Arash Eslamdoost

Chalmers, Mechanics and Maritime Sciences, Marine Technology

Lars Larsson

Chalmers, Mechanics and Maritime Sciences, Marine Technology

Rickard Bensow

Chalmers, Mechanics and Maritime Sciences, Marine Technology

Ocean Engineering

0029-8018 (ISSN)

Vol. 152 100-112

Driving Forces

Sustainable development

Areas of Advance

Transport

Energy

Infrastructure

C3SE (Chalmers Centre for Computational Science and Engineering)

Subject Categories

Vehicle Engineering

DOI

10.1016/j.oceaneng.2018.01.037

More information

Latest update

6/12/2018