1 Numerical Predictions of Global and Local Ice Loads on Ships and Comparison with Field Measurements Biao Su Department of Marine Technology, NTNU January 7 th, 2013 Author CeSOS Centre for Ships and Ocean Structures
2 Outline Motivation Numerical model Case studies Numerical results Improvement and extension of the model
3 Motivation Global ice load Local ice load
4 Numerical model Sea ice Level ice The definition of design ice conditions is simplified in most ice class rules (e.g. Finnish-Swedish Ice Class Rules) by using the equivalent level ice thickness
5 Numerical model Research on the numerical modeling of ice hull interaction and ship maneuvers in level ice can be found for example in: Valanto, 2001 Liu et al., 2006 Martio, 2007 Nguyen et al., 2009 Sawamura et al., 2010 Lubbad and Løset, 2011 Source: Valanto, 2001 Source: Liu et al., 2006
6 Numerical model Simplification A A Section A A Source: Riska, 2007
7 Numerical model Integration
8 Numerical model Iteration Icebreaking pattern Transverse icebreaking force Transverse ship speed
9 Numerical model F( t ) F( t ) F( t ) k 1 k 1, 0 k 1 F( tk 1) F( tk 1 ) 6 3, i 1 x( tk 1) 2 M+A B C F( tk 1) M+A ak B bk Solve equations of motion Update hull nodes t t No Detect the contact zones between ice and hull Update the forces F( t ) F( t ) k 1 k 1, i 1 Acceptable? F( t ) F( t ) F( t ) k 1, i 1 k 1, i k 1, i Yes Update ice nodes Next time step
10 Case studies Tor Viking II (Sweden) - Ship s performance and maneuverability (Su et al., 2010a&b) Icebreaker AHTS/IB Tor Viking II Full-scale ice trials (Riska et al., 2001)
11 Case studies MT Uikku (Finland) - Ice-induced frame loads (Su et al., 2011a&b) Icebreaking tanker MT Uikku
12 Case studies MS Kemira (Finland) - Ice-induced frame loads (Su et al., 2011c) Chemical tanker MS Kemira The distribution of 12-hour load maxima measured on board MS Kemira and the estimated long-term extremes (Hänninen, 2003)
13 Case studies CIVArctic vessel (MARINTEK) - Full-scale and model-scale comparison (Su et al., 2012) Comparison of the icebreaking patterns, running ahead in 22 mm (0.53 m in full-scale) thick level ice Comparison of the icebreaking patterns, running astern in 52 mm (1.26 m in full-scale) thick level ice
14 Case studies CIVArctic vessel (MARINTEK) - Full-scale and model-scale comparison (Su et al., 2012) R i P 3 R i M V P V M The ice resistance that the vessel encountered, running astern in the ice of increasing thickness The speed that the vessel could attain, running astern in the ice of increasing thickness
15 Case studies S.A. Agulhas II (South Africa) - Full-scale ice trials in March, 2012 Multipurpose vessel S.A. Agulhas II
16 Numerical results Icebreaking patterns (Tor Viking II)
17 Numerical results Ship s performance (Tor Viking II) - Ship speed (h-v curve) Ice thickness Shoulder crushing! Ship speed
18 Numerical results Ship s performance (CIVArctic vessel) - Turning circle diameter Heeling angle: 1 Even keel Heeling angle: 2
19 Numerical results Ship s performance (Tor Viking II) - Turning circle diameter Snow cover included 1000 900 800 Even keel Turning diameter [m] 700 600 500 400 300 Heeled Required value T=6.9 m 200 100 0 0 20 40 60 80 Ice thickness [cm] Full-scale turning tests with even keel and heeled (Riska et al., 2001)
20 Numerical results Local ice loads (MT Uikku) - Spatial distribution
21 Numerical results Local ice loads (MS Kemira) - Probabilistic distribution Source: Hänninen, 2003
22 Numerical results More results can be found in: [1] Su, B., Riska, K. and Moan, T., 2010a. A numerical method for the prediction of ship performance in level ice. Cold Regions Science and Technology, Vol. 60, pp. 177-188. [2] Su, B., Riska, K. and Moan, T., 2010b. Numerical simulation of ship turning in level ice. Proceedings of 29 th International Conference on Offshore Mechanics and Arctic Engineering (OMAE), Shanghai, China. [3] Su, B., Riska, K. and Moan, T., 2011a. Numerical simulation of local ice loads in uniform and randomly varying ice conditions. Cold Regions Science and Technology, Vol. 65, pp. 145-159. [4] Su, B., Riska, K. and Moan, T., 2011b. Numerical study of ice-induced loads on ship hulls. Marine Structures, Vol. 24, pp. 132-152. [5] Su, B., Riska, K. and Moan, T., 2011c. Numerical simulation of ships operating in level ice. Proceedings of 21 st International Conference on Port and Ocean Engineering under Arctic Conditions (POAC), Montreal, Canada. [6] Su, B., Riska, K., Moan, T. and Berg, T.E., 2012a. Full-scale and model-scale simulations of a double acting intervention vessel operating in level ice. Proceedings of 21 st IAHR International Symposium on Ice, Dalian, China. [7] Su, B., 2012b. Full-scale and model scale simulations of the level ice performance of CIVARCTIC Vessel. Report No. 530529, MARINTEK, Trondheim, Norway. [8] Su, B., 2012c. Model scale simulation of the floe ice performance of CIVARCTIC Vessel. Report No. 530529, MARINTEK, Trondheim, Norway.
23 Improvement and extension of the model Fluid-ice interaction during ice bending (Sawamura et al.) Source: Sawamura et al., 2010
24 Improvement and extension of the model Ice submersion and accumulation (Zhou et al.) Source: Zhou et al., 2012
25 Improvement and extension of the model Stationkeeping of a moored ship in level ice (Zhou et al.) Source: Zhou et al., 2012
26 Improvement and extension of the model 6-DOF ship s motions in level ice (Tan et al.) 3-DOF model 6-DOF model Source: Tan et al., 2012
Improvement and extension of the model Ice management: strategy and efficiency (Su et al.) Level ice Managed ice Illustration of two-stage ice management in front of a protected stationary vessel (Source: Hamilton et al., 2011) Source: Su et al., 2012
28 Thank you for your attention!