Sea spray icing
Top image: Anton Kulyakhtin at his field site near the Longyearbyen harbour. Photo: Eva Therese Jenssen/UNIS.
Sea spray icing is a dominant source of ice accumulation on ships and offshore installations and can be quite dangerous. PhD student Anton Kulyakhtin (24) from Russia performs field measurements in Longyearbyen which will be used for validation of a future 3D-model predicting ice accumulation on ships and floating structures.
24 May 2011
Text: Eva Therese Jenssen /UNIS
The activity level in Arctic waters is expected to increase significantly over the next decades. Oil- and gas explorations and increased shipping activity will introduce many new ships and offshore constructions in these waters.
More traffic in ice infested waters will expose vessels and offshore platforms to icing events. Icing on structures may occur when the air temperature is lower than the freezing point of sea water. Freezing of sea spray is generated when the ship’s hull slams an oncoming wave or waves slam into structures.
Proper predictions needed
Sea spray icing is a dominant source of ice accumulation on ships and offshore installations and can be quite dangerous. Icing on ships can in extreme cases affect the vessel’s stability and may cause ships to capsize and sink. But it is not only a danger to ships, it is also a challenge for marine operations and crews onboard ships. Icing on deck makes its surface slippery, thus work on deck becomes difficult and dangerous.
To reduce the risk of icing events, proper predictions of icing conditions is needed. Icing modelling can help predict the ice accumulation rate and be a helpful tool in designing of ships and rigs. This can help save ships and human lives.
The ultimate goal is to create a new 3D ice accretion model. This model is to be used for the production of a large scale model for the prediction of icing on ships and offshore structures.
Small-scale measurements in Longyearbyen
This is what Anton Kulyakhtin’s PhD project is all about. The NTNU and UNIS student has been spending the last couple of months performing small scale measurements in the Longyearbyen harbour area.
The construction set up in the harbour is designed by Kulyakhtin and professor Sveinung Løset. The cylinder is designed to modulate a ship rail. The construction pumps up sea water to spray water on the cylinder within a distance of about 5 m.
In addition, Kulyakhtin measures the weather conditions. For instance, the wind defines the amount of water sprayed and the temperature influences the ice formation.
He is also investigating the salinity of the ice and the ice density. The density of atmospheric icing is lighter, with the ice having a lot of air bubbles inside the ice, whereas the icing from sea water is denser due to the high salt content and less porosity.
The data collected will now be analyzed. He will conduct similar field experiments at the end of the year to get more data for a future model.
-The ultimate goal is to develop a model that will describe ice build-up on ships and large structures, and predict how much ice will accumulate due to the weather conditions. When should a ship set sails so to speak and when should it stay in the harbour, Kulyakhtin explains.
-The model will be basic, a simple model for simple structures. In the longer run, hopefully we will develop more complex models that can simulate icing on all types of ships or large offshore structures, Kulyakhtin says.
The PhD project is expected to be completed in 2012. Anton Kulyakhtin wants to thank the Harbour Authorities in Longyearbyen for being very helpful in facilitating the experiments.