Session: 06-12-01 Ship Hydromechanics I

Paper Number: 101675

101675 - A 4 Degree of Freedom Velocity / Power Prediction Program for Wind (Assisted) Vessels 

Ships driven or assisted by wind propulsion system sail at high drift angles. This is necessary to
generate a transversal force to balance the transversal force from the wind propulsion system. However,
it is important to generate the sufficient transversal hull forces with drift angles as low as possible.
Additionally, the transversal force should be generated by the hull in oblique flow without causing a
huge yaw moment, which would have to be compensated with large rudder angles, which in turn would
cause an increase in longitudinal resistance. This results in an additional target in the design process
which must be observed in the early design state. Therefore, the transversal force of the hull in oblique
flow has to be calculated in a fast and sufficiently accurate way under consideration of the hull shape to
determine the power savings of wind assistance or the achieved ship speed of a wind-propelled vessel.

This paper presents a velocity prediction program (VPP) respectively a power prediction program (PPP)
for ships driven or assisted by wind propulsion systems named ”E4-SAIL”. The program balances the
forces acting on the ship in the 4 degrees of freedom (4DOF) surge, sway, roll and yaw. Therefore,
environmental forces caused by wind, current and sea state can be considered. The VPP/PPP is embedded
within the design tool ”E4”, so the prediction can be refined directly within the design process whenever
more information on the ship is known. Thanks to the integration into the design environment, the
calculation of the transversal forces acting on the hull and the forces due to the sea state takes into
account the shape of the hull and uses not only an amount of ship parameters. Because the VPP/PPP
is intended for use in the early design stage, the calculations have to run very fast, so that the effect of
several changes in hull form and floating position could be easily checked during the design process. In
this paper the calculations of the individual force components are presented and the restrictions of the
calculation methods are discussed. Furthermore, calculations of the VPP are presented and compared to
full scale measurements.

The paper is original and for the first time presented in public.
 

Presenting Author: Johannes Oettle Hamburg University of Technology

Presenting Author Biography: The author graduated from Hamburg University of Technology with a masters degree in Naval Architecture and Ocean Engineering in 2020. Since 2021, the author has been working as a research assistand at the Institute of Ship Design and Ship Safety at the Hamburg University of Technology.

Authors:

Johannes Oettle Hamburg University of Technology
Stefan Krüger Hamburg University of Technolohy