NEWSWAVE - HSVA

6 NEWSWAVE 2006/2
RESEARCH PROJECT “SINSEE”
SUCCESSFULLY FINISHED
by Walter L. Kuehnlein
Final results of the German research project “SinSee” were presented
at a colloquium held at HSVA on June 22nd. Within the framework of
“SinSee”, HSVA cooperated with four partners
(FSG, TUB, TUHH, and OceanWaves) on the
evaluation of safety issues of vessels in severe seas.
Topics like numerical analysis and
simulation, validation by means of
model test investigations, full scale
measurements and evaluation of capsizing
risks were covered within this project.
Available means for investigating the
sea-keeping performance of vessels are
model tests and/or numerical simulations.
Both model tests and numerical motion
simulations are often used post-accidental
in order to investigate the causes. Standard
seakeeping tests (tank or numerical) are
available for investigating several phenomena
such as slamming, green water, capsizing,
etc. but are only occasionally used –
mainly for rather unusual designs, or in
cases where sea keeping characteristics are
more vital than for standard vessels.
Within the research project “SinSee”,
HSVA developed the following concept of
computer controlled capsizing tests in
order to ensure that the processes of large
rolling and capsizing take into account the
following wave characteristics:
➢ Extreme wave height and wave steepness,
➢ Wave grouping, and
➢ Propagation velocity and direction.
Unfavourable phase relationships between
wave components as well as wave / structure
interactions may lead to dangerous situations
such as:
➢ Loss of stability at the wave crest,
➢ Resonant excitation, especially
parametric rolling, and
➢ Broaching due to a loss of course
stability.
The analysis of this complex, non-linear
behaviour puts high demands on the
capsizing test set-up and procedure:
➢ Exact correlation of cause (wave
excitation) and reaction (ship motion),
➢ Reproducibility, high accuracy of
measurement and control units,
and
➢ Deterministic performance of test
events.
These demands require a highly sophisticated
testing procedure. Figure 1
shows a schematic test configuration for
computer controlled seakeeping tests.
Three main system components have to
be coordinated:
➢ Wave maker,
➢ Towing carriage (including the transverse
carriage), and
➢ Ship model.
In head seas, the ship is positioned at
the end of the tank opposite to the
wave maker. In seas from astern, the
ship model has to wait close to the wave
maker until a defined sequence of the
wave train has passed.
The ship model is controlled by the
master computer which via telemetry
commands a z-manoeuvre at constant
course angle and model velocity. These
test parameters as well as the model
sea parameters are chosen according to
the metacentric height GM of the
model, the expected rolling mode and
occurrence of resonance. Both the towing
carriage and the transverse horizontal
carriage are computer controlled.