Feasibility study of a semi-empirical simulation model for level ice-breaking

Transcription

1 Kemi Arctic Feasibility study of a semi-empirical simulation model for level ice-breaking Floris Goerlandt Lauri Kuuliala, Pentti Kujala Aalto University Department of Applied Mechanics, Marine Technology

2 Presentation overview Models for ship performance in ice Methods for simulating ship performance in level ice Physical and mathematical basis of the method Research questions Results and conclusions

3 Models for ship performance in ice SEMI- EMPIRICAL MATHEMATICAL MODELS DATA-DRIVEN MODELS BASED ON FULL SCALE AIS, ICE AND SHIP DATA SEMI- EMPIRICAL, PHYSICS- BASED SIMULATION MODELS Lindqvist 1989 Riska et al Montewka et al Valanto 2001 Sawamura et al Su et al Lau et al Tan et al. 2013

4 Semi-empirical simulation models for level ice-breaking Valanto 2001 Sawamura et al Su et al Lau et al Tan et al. 2013

5 Physical and mathematical basis of the method 3 degree of freedom ship dynamic model for ship performance and ice loads in level ice Coupled differential equations Time domain simulation Force-balance equations of motion Su et al. 2010

6 Physical and mathematical basis of Ice parameters Coefficient of friction Poisson s ratio Strain modulus Crushing strength Bending strength Thickness the method Input parameters Force models t>t_end YES Save results EOM solver NO Advance time NO Update location and motions. Update ice field geometry YES Excitation converges? INPUT PARAMETERS Ship parameters Ship hull parameters Length of waterline Breadth of waterline Draught Block coefficient Entrance waterline angle Flare angle at bow Hull normal angle at bow Mass of displacement Moment of intertia about z-axis Added mass matrix Damping matrix Bollard pull Open water speed

7 Physical and mathematical basis of the method Input parameters FORCE MODELS Hydrodynamic forces NO Force models t>t_end YES Save results EOM solver NO Advance time Update location and motions. Update ice field geometry YES Excitation converges?

8 Physical and mathematical basis of the method Input parameters FORCE MODELS Ice model: icesheet contact NO Force models t>t_end YES Save results EOM solver NO Advance time Update location and motions. Update ice field geometry YES Excitation converges?

9 Physical and mathematical basis of the method Input parameters FORCE MODELS Ice crushing and friction NO Force models t>t_end YES Save results EOM solver NO Advance time Update location and motions. Update ice field geometry YES Excitation converges? Linear crushing force model Non-linear crushing force model

10 Physical and mathematical basis of the method Input parameters FORCE MODELS Ice bending NO Force models t>t_end YES Save results EOM solver NO Advance time Update location and motions. Update ice field geometry YES Excitation converges? C f, C l and C v Empirical constants

11 Physical and mathematical basis of the method Input parameters FORCE MODELS Ice submerging NO Force models t>t_end YES Save results EOM solver NO Thrust model Advance time Update location and motions. Update ice field geometry YES Excitation converges?

12 Physical and mathematical basis of the method Input parameters NO Force models t>t_end YES Save results EOM solver NO Advance time Update location and motions. Update ice field geometry YES Excitation converges? NUMERICAL SOLVER FOR EQUATIONS OF MOTION

13 Physical and mathematical basis of the method Input parameters NO Force models t>t_end YES Save results EOM solver NO Advance time Update location and motions. Update ice field geometry YES Excitation converges? BOOKKEEPING Update ship location and motions Update ice field geometry Update time step Save results

14 Physical and mathematical basis of the method Input parameters MODEL OUTPUT Updated position of ship and ice sheet NO Force models Time history of force components t>t_end YES Save results EOM solver NO Advance time Update location and motions. Update ice field geometry YES Excitation converges? Time history of velocity components

15 Research questions How feasible is the use of the presented model in ship design stage For ship resistance prediction? For ice loads prediction? Particularly Empirical coefficients C f, C l and C v based on best estimates Ice crushing model Fc: linear or non-linear Method: Parameter sensitivity study Comparison: calculated ice loads with full scale measurements crushing force models systematic study

16 Results Reality check: Ice breaking pattern

17 Results Ice resistance

18 Results Ice resistance

19 Results Attainable speed versus ice thickness

20 Results Ice contact lengths

21 Results Ice loads: parameter sensitivity

22 Results Ice loads: comparison with full scale Time history Distributions of peak line loads Maximum line load

23 Conclusions Empirical coefficients Ship performance: noticeable effect Ice loads: very significant effect No clear trends in parameter combinations Crushing force model Ship performance: minor effect Ice loads: very significant effect Comparison with full scale Shape and size of ice floes is quite reasonable, but simplified Maximum predicted loads significantly affected, especially at higher ice ticknesses

24 Conclusions The method can be used with some confidence for ship performance prediction [added value?] Ice load prediction involves large uncertainty Focus on justifying the values for the empirical coefficients Accounting for uncertainty in prediction Su et al. 2010

25 Kemi Arctic Feasibility study of a semi-empirical simulation model for level ice-breaking Floris Goerlandt Lauri Kuuliala, Pentti Kujala Aalto University Department of Applied Mechanics, Marine Technology