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1 INTRODUCTION
As more ports are targeting to accommodate larger
ships at deeper drafts, there has been lots of pressure
on port planners to increase the port access channel
capacity through capital dredging. The main focus of
such capital dredging attempts is typically deepening
the channels as changing the horizontal profile of
navigation channel is considered to be the expensive
element. Consequently, ships are entering the port
waters with larger drafts, length and breadth while
the channel profile remains largely unchanged.
Resulting in higher risk in handling and
manoeuvering, especially when combined with
extreme weather events. Although in channel
development plans, minor modifications are made on
bend configuration, still there are lots of risk in
navigating big vessels through port waters. NCOS
ONLINE Manoeuvring Module [8] is a cloud based
online operational decision support tool that brings
the capabilities of real time manoeuvring simulation
of FORCE Technology’s SimFlex4 [10] to fast time
simulation, assisting the port operators to identify
risks in pilotage of big vessels under the
environmental forcing within shallow and confined
waterway.
Development and Validation of an Operational Fast
Time Ship Manoeuvring Solver to Increase Navigation
Efficiency in Horizontally Restricted Waterways
M
. Fathi Kazerooni
1
, M. Rahimian
2
, M. Tree
2
, T. Womersley
2
, S. Mortensen
2
& B. Jensen
3
1
DHI Water & Environment, Brisbane, Australia
2
DHI Water & Environment, Gold Coast, Australia
3
FORCE Technology, Brondby, Denmark
ABSTRACT: Growth of demand for containerized cargo shipping has put more ports into pressure to
accommodate larger vessels. Considering the limitations on dimensions of navigation channels, this is not
feasible unless aiming for significant capital dredging or alternatively creating high precision predictions of
vessel motions subjected to environmental forcing and interaction with shallow and restricted waterway. NCOS
ONLINE (Nonlinear Channel Optimisation Simulator) is a state of the art navigation support tool which
combines DHI’s high level forecast of environmental conditions with mathematical model of ship motions to
add an extra level of accuracy in predicting the under-keel clearance and vessel swept path to boost the
efficiency of navigation and pilotage within restricted channels. NCOS Manoeuvring Module utilizes an
autopilot scheme based on PID (Proportional / Integral / Derivative) controller and Line of Sight Algorithm to
FORCE Technology’s SimFlex4 manoeuvring solver for prediction of manoeuvring ship swept path and
response, which will effectively bring the accuracy of real time full bridge simulator to fast time operation
support tool. In this paper, the result of mathematical model is validated against fullscale measurements of
containership transits through Port of Auckland Navigation channel by comparing pilot commands, leeway
drift and swept path through output of portable pilotage unit. According to the results the model is found
promising to predict the behaviour of human pilots with precision required in operational use. Finally, the
swept path and manoeuvring performance of a sample transit is assessed on different environmental conditions
and tide stages to evaluate the safe transit windows in operation.
http://www.transnav.eu
the
International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 17
Number 1
March 2023
DOI: 10.12716/1001.17.01.
06
72
Both real time and fast time manoeuvring solvers
are generally based on the determined hydrodynamic
coefficients that come from captive model tests in a
towing tank or planar motion mechanisms [1]. Most
recently CFD application has been of interest as an
alternative for towing tank model tests [2]. However,
as it is difficult to take into the account the interaction
of propulsion and steering with vessel main hull,
these mathematical models should be validated before
using in manoeuvring solvers. Towing tank
experiments usually suffer from model scale effects,
and as the viscous effects in manoeuvring are not
fully understood, there would be a high level of
uncertainty when extending these results to fullscale
[3], There have been several attempts for validating
the manoeuvring mathematical models. Free-running
model tests can provide a higher level of accuracy as
the size of the model is not restricted by carriage
equipment in the tank and models are typically made
in larger scales [4]. Although the scale effects for hull,
rudder and propeller are still important in free
running model tests, the interaction of hull, propeller
and rudder are fully considered in free running model
tests. Validation of manoeuvring mathematical
models through this method shows more course-
stability than measurements [5,11].
Standard ship manoeuvering tests in fullscale are
considered as part of ship delivery sea trials [6], and
the results are made available through pilot cards or
wheelhouse posters. These results are often used for
validation of ship manoeuvering simulation models
[7]. Although sea trial results are good for developing
manoeuvering models, there are still several reasons
that they cannot be considered as a good measure for
validating fast or real time manoeuvring solvers. The
sea trial is typically handled in deep water as
executing the tests in shallow waters is risky, and in
most cases the vessels are in ballast or half-laden
condition, where the manoeuvering characteristics
can’t be easily scaled to deeper drafts.
NCOS ONLINE Manoeuvring Module is DHI’s