FOUNDATION
FOR SAFETY OF NAVIGATION AND ENVIRONMENT PROTECTION
International Workshop on
DYNAMIC STABILITY CONSIDERATIONS IN SHIP DESIGN
HELD IN
13-16 September 2009
PROCEEDINGS
ILAWA 2009
ORGANIZING COMMITTEE:
Chairman:
Scientific Secretary: Miłosz Frackowiak, Assistant Professor,
INTERNATIONAL COMMITTEE AND PARTICIPATION:
Vadim
Belenky
Naval
Bulian
Gabriele
Dept. of Naval Architecture, Ocean and Environmental Engineering (DINMA),
Chris
Bassler
Naval
Frąckowiak Miłosz
Techical University of
Francescutto Alberto, Dept.
of Naval Architecture, Ocean and Environmental Engineering (DINMA),
Grochowalski Stefan, Polish Register of
Shipping,
Hinz
Tomasz , Polish Register of
Shipping,
Kobyliński Lech, Foundation for
Safety of Navigation and Environmet Protection,
Kostas
Spyrou
Szozda
Zbigniew
Marine Academy, Szczecin, Poland
Umeda
Naoya
Department of Naval Architecture and OceanEngineering,
Yamamura
Shinya
Department of Naval Architecture and OceanEngineering,
©
Copyright by Foundation of Safety of Navigation and Environment Protection 2009
ISBN
83-922935-1-7
Electronic version only.
PREFACE
The
world’s fleet is changing and responding to market needs, geometries of novel
ship designs have become considerably different from “conventional” forms. These
considerable differences in geometry may invoke dynamic behavior that is
drastically different from historical experience.
A classic
example of this phenomenon is parametric roll of large containerships. The
buttock flow stern with large overhang and well-developed bow flare provides a
natural solution for a combination of requirements that includes relatively high
speed, volumetric capacity, and fuel economy. However, such a hull form is
characterized by significant changes of waterplane area and shape in
longitudinal waves. Periodically changing stability places the ship into
principal parametric resonance, either in head or following seas, depending on
loading conditions and speed. Capsizing still seems unlikely for these large
ships; however, large roll angles and accelerations may pose an obvious danger
for both cargo and crew. Such behavior is outside of historical expectations for
a ship; therefore dynamic stability concerns are well grounded.
Another
phenomenon related to changes of waterplane is pure loss of stability, when a
prolonged sailing near the wave crest may cause significant roll angles or even
capsizing. Increased speed also elevates the danger of broaching for types of
vessels where it would not be expected otherwise. A ship of novel design may
exhibit unexpected behavior, even in the case of well-studied dead ship
conditions.
Because
the cause of these problems is rooted in hull geometry, increased awareness of
potential problems is needed relatively early in the design stage. However,
sometimes these problems cannot be solved with design modifications, due to
additional constraints. In this case, the risks posed by such behavior need to
be evaluated and ship-specific operator guidance may be needed to help the crew
attempt to avoid dangerous situations where the ship may become dynamically
unstable.
While
working with these new designs, it is important to remember that existing
stability standards are based mostly on previous experience. So when geometry
and/or operations depart significantly from the historical experience, the
applicability and safety margin of existing criteria may no longer be as
comprehensive.
These
stability failures are essentially large motions and accelerations phenomena
occurring in random seas. The challenge is that these phenomena result from a
significantly nonlinear dynamical system under stochastic excitation. These
types of problems can be solved by direct assessment methods: either by a model
test or numerical simulation with an advanced hydrodynamic code in time-domain.
However, direct assessment is expensive and time-consuming. Because the design
process often includes the analysis of many alternatives, application of direct
assessments has to be well-justified.
It means
that a designer should also have relatively simple tools that allow quick
evaluation to determine if a proposed design may be vulnerable to stability
failures related to these phenomena. If such a tool indicates possible dynamic
stability problems, for example, caused by parametric roll or broaching, then
application of direct assessment methods can be formally justified.
For
different modes of stability failure, it may be appropriate to have such tools
be of several levels of different complexity, ranging from simple formulae to
computer software. Simple tools need to be more conservative, so if a
first-level analysis shows no vulnerability to a particular type of stability
failure, it means that this type of failure is practically impossible for this
type of ship. If a first-level analysis indicates possible problems, then the
second-level method is applied and so forth, until the direct assessment is
found to be necessary. The outcome of this analysis is either a change of design
or the development of ship-specific operational guidance.
Design
tools for first and second level vulnerability analysis were the primary focus
of this workshop. However, some contributions also considered direct assessment
analysis and the development of ship-specific operational guidance.
The
contributions from leading experts included in the proceeding of this workshop
may be useful for organizations and individuals involved in the development of
new generation of stability criteria and related design tools.
Prof. L.
Kobylinski,
Chair of
the Organizing Committee
CONTENTS
1.
PURE LOSS OF
STABILITY
1.
Vadim Belenky, Christopher Bassler:
Vulnerability level 2
criterion for pure-loss of stability
2.
Gabrielle Bulian,
Alberto Francescutto:
Vulnerability to
pure loss of stability in following waves: ideas for a framework
2.
PARAMETRIC ROLL
1.
Vadim Belenky , Christopher Bassler :
Vulnerability level 2
criterion for parametric roll
2. Naoya
Umeda, Y. Sogawa, T Tsukamoto: New
generation intact stability criteria- Parametric rolling
3. Gabrielle Bulian,
Alberto Francescutto:
An assessment methodology for 1st level vulnerability check with
respect to parametric rolling
3.
SURF-RIDING. BROACHING
1.
Naoya Umeda, Atsuo Maki, Hiroyouki Sano:
New generation intact stability
criteria- broaching
2.
Shinya Yamamura, Atsua Maki, Naoya Umeda, Hiroyouki Sano:
Numerical study towards
physics-based criteria for avoiding broaching and capsizing in
following/quartering waves
4.
DEAD SHIP
CONDITION
1. Naoya Umeda, S. Izawa.
2. Gabrielle Bulian,
Alberto Francescutto, Alessandro Maccari:
An
approach for 2nd level vulnerability criteria for dead ship condition
5.
OTHER IDEAS
ON FUTURE STABILITY CRITERIA
1. Naoya Umeda: New generation intact stability criteria – general structure
2. Stefan
Grochowalski,
Tomasz Hinz:
Development
of
new
intact
stability
criteria. Comments
on
some
factors
affecting
dynamic
stability
of
ships
in waves.
3. Vladimir Shigunov, Ricardo Pereira: Direct assessment procedure and operational guidance for avoidance of cargo loss and damage on container ships in heavy weather
4.