MARIN has experimented with artificial ice in recent model test campaigns to give the industry better insight into working in inhospitable environments.


Artifi cial ice research provides fresh insight


1.0 Normalized power (-) 0.5


Power required to sail ship through ice field plotted for different ice coverage percentages


Normalized floes energy, coverage = 60%


100 150


0.6 50


-150 -100 -50 0


0 100 200 300 400 500 600 0 0.5 1.0 1.5


Normalized position in ice field (-)


0.3 0.4 0.8 0.4


100 90 80 70 60 50 40 30 20 10


0.2 0.2


O


ver the past few years as the maritime and offshore industry moves into more challenging


environments where ice is often prevalent, MARIN has placed increasing importance on researching operations in ice. As part of this on-going ice research, MARIN recently experimented with the use of artificial ice in several test campaigns1&2


.


The main aim is not to obtain an alternative for ice model basin tests but to give insight into the involved processes and to provide validation material for numerical simulations. The advantage of artificial ice over cold model ice is the fact that the properties of the material are constant and known. Moreover, it offers the opportunity to make a comparison


Solange van der Werff & Auke Ditzel s.v.d.werff@marin.nl


between model tests results and simulation results in a relatively straightforward manner because both approaches are based on the use of rigid particles.


All the model tests were conducted at the MARIN facilities, whereby MARIN experts worked together with Delft University of Technology bachelor students. In the tests a ‘pre-broken’ artificial ice channel was made, consisting of hundreds of rigid polypropylene (PP) particles in a fishbone pattern. Large PP plates kept the channel together on both sides. A model was towed through the channel, while maintaining constant and equal distance from both plates.


Submersion resistance To get through the channel, the model had to submerge the PP particles, causing a certain resistance, which is referred to as submersion resistance.


18 report


According to the Lindqvist formulation3


,


total ice resistance is a superposition of the submersion resistance and the breaking resistance (which was not present given that the artificial ice was already broken).


With the Lindqvist formulation it was possible to assess whether the measured submersion resistance was close to what it should be. In 2013 this measured resistance was found to be too large and this was probably caused by particles regularly sticking to the hull and being dragged along with the mod- el. Therefore, in 2014 MARIN investigated whether a different coating on the model could reduce the ‘stick-slip’ behaviour and thus reduce the measured submersion resistance.


After conducting friction tests at TU Delft a coating was selected and the same model


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