HANSA 03-2024

SCHIFFSTECHNIK | SHIP TECHNOLOGY
based on full-scale data. This application is in line with the initial
vision of ISO 19030, as it focusses on »classic« eneryg saving devices,
like wake-equalizing ducts.
Mads Martinsen (Mærsk Mc-Kinney Møller Center for Zero Carbon
Shipping) look from a ship operator’s side on Performance of
energy efficiency technologies retrofitted on containerships. Other
presentations look at energy saving retrofits which used to be considered
to be exotic, but are increasingly considered in view of the
CII crunch. Ruth (DNV) look at Long-term verification of ALS and
WASP systems. ALS stands for air-lubrication systems, WASP for
wind assisted ship propulsion. Both options have enjoyed exponential
growth in shipping over the past 5 years, and are expected to see
continued exponential take-up in shipping.
Especially for WASP systems, the business case is often difficult
to establish due to high uncertainties, as energy savings depends
highly nonlinearly on ship speed and operational area. Masutani
(Sumitomo) elaborates on this in Navigating a sustainable future
with wind-assisted ship technology: NAPA, Norsepower, and
Sumitomo‘s collaborative journey. The business case is there,
often, but sophisticated performance monitoring is the best approach
to quantify it.
Artificial intelligence
»Ebony and ivory, living in perfect harmony« came to my mind
looking at the papers of this year’s HullPIC. Not thinking about a
piano keyboard, but how the discussion on black-box models
based on Artificial Intelligence and white-box models based on
first-principles CFD simulations has evolved since 2016.
There had been controversy around Artificial Intelligence in
performance monitoring already during the development of
ISO 19030. The standard accepted CFD simulation as a standard
approach to establishing baselines, i.e., the speed-power
curves defining the ship’s calm-water performance for various
drafts. Methods based on machine learning from data collected
on ships, on the other hand, were relegated to Part 3 of
the standard, deemed to be not mature enough or not enough
independent experience was available to judge accuracy and
reliability. Both first-principles and machine learning approaches
continue to be developed, but a notable trend is the
combination of the two, exploiting the respective strong points
of both approaches.
CFD is very valuable for insight into flows, and we continue
to gain insight into CFD through dedicated validation data, ultimately
increasing accuracy and reliability of CFD approaches
which continue to become increasingly accessible, also in
terms of cost. Most CFD validation has been against model
tests, for good reasons. Model tests allow controlled ambient
conditions and detailed measurements of flow details are easier.
Alas, ship hydrodynamicists are well aware of the scale effects,
making the flow around the full-scale real ship quite different
from model-scale flows. While results for model tests are
quite close together, extrapolations to full scale show much
larger scatter.
Dmitriy Ponkratov (JoRes) presents What did we learn from
the ship scale blind CFD validation exercise? There is indeed
much to learn, both because the JoRes team openly shares the test
case data and results, allowing other CFD groups to test their approaches.
»Blind« tests are particularly insightful, as the simulators
do not know the experimental results ahead of their computations.
Thus, there is no chance to tweak parameters until
good agreement with experiments is achieved.
Deep dive into trim optimisation
Inno Gatin (Cloud Towing Tank) takes a Deep dive into trim optimisation:
Physical phenomena behind the fuel savings. Trim optimization
shares the need for baseline curves with performance
monitoring. Parallel computation in numerical towing tanks,
using the cloud for computing power, has brought down costs for
such systematic computations considerably. The computations
are often used as a standard building block in state-of-the-art per-
Dein Partner für
Bunker-Service
Betriebs- und Schmierstoffe für den
sicheren Betrieb Deiner Flotte.
Infos unter:
Tel. +49 40 53798470
hoyer-marine.de
HANSA – International Maritime Journal 03 | 2024
45