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• ANNUAL REPORT 2013
the OATRC2013 expedition to the Greenland Sea. Here
he carried out experiments on the flow of ice in the wake
of the icebreaker.
The development of his numerical model started in
the beginning of 2013 and its preliminary concept was
presented on the International Conferences on Port
and Ocean Engineering under Arctic Conditions in June
2013. After that, considerable efforts were made to
implement the mathematical model in a numerical tool
that now can be used to analyse the motions of multiple
rigid bodies in a fluid.
Validation is an important step in the development of
reliable numerical models which often includes the
comparison of numerically predicted results with the
corresponding data obtained during physical model
tests. In the autumn of 2013, these model tests were
done by a number of towing-tank experiments at the
Harbour and Coastal Laboratories at the Norwegian
University of Science and Technology (Figure 3a) in
order to investigate the hydrodynamic action of a float-
ing structure on submerged ice masses.
In order to study the free surface effect, there were also
several trials in a restricted area with artificial ice cover
represented by paraffin floes. The set-up used in the lab
consisted of a towed cylinder that represents a floater
and a fully submerged sphere (ice mass) mounted on
a three-axial load cell resting on a stiff leg which was
fixed to the flume bottom. The surge and sway forces on
the ice that occurred in response to the passage of the
cylinder were measured as the main indicators of the
hydrodynamic interaction. The main parts of the set-up
for the physical model tests were also reproduced in
the numerical model to simulate the case. Both sets of
obtained data were successfully compared with each
other as shown in Figure 3b. The results of this work
demonstrated the capability of the developed numerical
model to reliably predict hydrodynamic forces and also
indicated the limits of the model’s applicability.
The developed numerical tool is now being used by
Tsarau to analyse local concentrations of managed ice
floes along the hull of a tanker (Figure 4). This case
represents typical problems that may occur during
offloading operations into a transit tanker or during
station keeping of a vessel in ice-covered waters.
Figure 3a. Experiment set-up at one of the flumes at the Harbour and Coastal Laboratories, NTNU. Studies of hydrodynamic
interactions between a floating structure and artificial ice masses.
Figure 3b. Physical model tests vs numerical simulations.
Photo: Andrei Tsarau