Ice tank

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An ice tank is a ship model basin whose purpose is to provide a physical modeling environment for the interaction of ship, structures, or sea floor with both ice and water. Ice tanks may take the form of either a towing tank or maneuvering basin.

Many un-refrigerated ship model basins use ice simulants such as paraffin wax, plaster, and mixtures of foam or plastic beads. The cleanup and handling of such simulants often proves cumbersome. What differentiates an ice tank from other ship model basins is that an ice tank has purpose built provisions into its structure for handling such material conveniently. Use of a refrigerated basin containing mostly water allows freezing and melting to be a convenient method of model ice preparation and cleanup.

Ice scaling[edit]

Ship model basins often simulate full-scale processes in miniature. Ships and structures are reduced linearly in size, and cubic in mass, displacement, and volume. The challenge in ice modeling is correctly reducing the ice properties of interest to provide an accurate simulation.

Many factors and properties are of interest when simulating ice. The actual environment that will be simulated is of prime concern. For example, ice pieces flowing then jamming a spring river would be modeled very differently from a ship model traversing a simulated arctic ice sheet. Different again would be a ship traversing an area of loose broken ice pieces or pack ice.

Weakened ice method[edit]

One important factor in icebreaker model testing is the effect of changing ice strengths and thickness. For example: if a 1 to 30 scale is chosen, then the ship model is 1/30 the size. The ice used must also be 1/30 the thickness and 1/30 the strength.

If one was to use pure-water ice, the problem is that pure-water ice does not soften.

Many ice tanks simulate ice using a mixture consisting mostly of water and chemical additives called dopants, which are chemicals which reduce the melting temperature of pure water ice. Common dopants used are salt, ethanol, ethylene glycol, and urea.

By using a sufficiently cold temperature, both water and dopant are frozen in solution together forming an ice sheet. This impure ice sheet is inherently softer than pure-water ice but may be much harder than the scale strength desired. Once a desired thickness is achieved, the air temperature is raised to a tempering temperature. As the temperature of the ice rises the dopants come out of frozen solution and form liquid brine pockets. These brine pockets slowly drain out of the ice sheet thus weakening it. Provided the ice-sheet isn't allowed to refreeze, the strength of the ice continues to decrease approaching an asymptotic value. Choosing a correct ice scale then becomes a question of when to conduct the test. This softening is often referred to as tempering.

Different ice simulants model ice differently. For example, most icebreakers break ice by riding upward unto the ice and breaking downward by the weight of the vessel. In this case, correctly modeling ice's downward flexural strength is most important.[citation needed] In the case of bridges or offshore structure, compressive strength or upward flexural strength may be of more interest. The effects of ice on ship propulsion often require model ice density to be reduced by adding controlled amounts of gas or air during the freezing process.

List of ice tanks[edit]

Facility Location Years Length Width Depth Technology Notes Ref
Aalto University Espoo, Finland 1980s–present 40 m (131 ft) 40 m (131 ft) 2.8 m (9 ft) Fine-grained with ethanol Undergoing renovations as of 2016 [1]
Korea Research Institute of Ships & Ocean Engineering (KRISO) Daejeon, South Korea 42 m (138 ft) 32 m (105 ft) 2.5 m (8 ft) [2]
National Research Council of Canada (NRCC-IOT) St. Johns, Newfoundland, Canada 90 m (295 ft) 12 m (39 ft) 3.0 m (10 ft) [3]
HSVA, Large Ice Model Basin Hamburg, Germany 78 m (256 ft) 10 m (33 ft) 2.5 m (8 ft) [4]
Aker Arctic Technology Inc Helsinki, Finland 2006–present 75 m (246 ft) 8 m (26 ft) 2.1 m (7 ft) Fine-grained with salt [5]
Masa-Yards Arctic Research Centre (MARC) Helsinki, Finland 1982–2006 77.3 m (254 ft) 6.5 m (21 ft) 2.3 m (8 ft) Fine-grained with salt Wärtsilä Arctic Technology Centre (WARC) until 1989; Aker Arctic since 2005. [5]
Wärtsilä Ice Model Basin (WIMB) Helsinki, Finland 1969–1982 50 m (164 ft) 4.8 m (16 ft) 1.15 m (4 ft) Saline water Built inside an old air raid shelter [5]
CRREL Hanover, New Hampshire, United States 37 m (121 ft) 9 m (30 ft) 2.4 m (8 ft) [6][7]
NMRI Mitaka, Tokyo, Japan 35 m (115 ft) 6 m (20 ft) 1.8 m (6 ft) [8]
Krylov State Research Centre St. Petersburg, Russia 102 m (335 ft) 10 m (33 ft) 2 m (7 ft) [9][10]
HSVA, Environmental Test Basin Hamburg, Germany 1971– 30 m (98 ft) 6 m (20 ft) 1.2 m (4 ft) [5][11]
National Research Council of Canada (NRCC-CHC) Ottawa, Ontario, Canada 21 m (69 ft) 7 m (23 ft) 1.1 m (4 ft) [12]
Arctic and Antarctic Research Institute (AARI) St. Petersburg, Russia 35 m (115 ft) 5 m (16 ft) 1.8 m (6 ft) [13]
Arctic and Antarctic Research Institute (AARI) Leningrad, Soviet Union 1955–?? 13.4 m (44 ft) 1.85 m (6 ft) 1.1 m (4 ft) Saline water World's first ice tank. [5]

References[edit]

  1. ^ Aalto Ice Tank. Aalto University. Retrieved 2016-10-16.
  2. ^ [1]
  3. ^ [2]
  4. ^ "HSVA Home - Hamburgische Schiffbau-Versuchsanstalt". Retrieved 15 October 2016. 
  5. ^ a b c d e 40 Years of Model Testing. Aker Arctic. Retrieved 2016-10-16.
  6. ^ [3]
  7. ^ [4]
  8. ^ "National Maritime Research Institute - Main Facilities". Retrieved 15 October 2016. 
  9. ^ "Krylov State Research Centre". Retrieved 15 October 2016. 
  10. ^ "Experimental facilities". Retrieved 15 October 2016. 
  11. ^ [5]
  12. ^ [6]
  13. ^ [7]