Correction of ship speed by ice compression effect
Ice pressure is exerted on a ship when ice floe is compacted due to wind and current. That will prevent ship progress and maneuvering. Ice pressure acts as side force when the ice-breaking vessel breaks the ice sheet. The side force causes frictional force between ship hull and ice and decreases the ship speed. The influence of ice pressure against the ship speed is incorporated in NEWSIM2 and then the relation between ice index and the influence was investigated.
The influence of ice pressure is considered when the total ice concentration equals 10.The adjust parameter Cco is shown in Table 2.6.8. The friction coeflicient between ship and ice is assumed 0.1, and the speed of ice flow is assumed 0.3m/sec. Here, the adjust parameter Cco is multiplied to the ship speed.
2.6.5 Development for the charts of ice index v.s. ship speed
Figure 2.6.8 to 2.6.11 shows the relations between the ice index and the ship speed of each service ship and escort icebreaker. Table 2.6.8 summarizes the input data set for NEWSIM2. Tables corresponding to Figure 2.6.8 to 2.6.11 are listed in the Appendix B. Ship speeds corresponding to arbitrary width of ice index were distributed within some range of speeds, thus the discrete probability distribution of the ship speed responding to every two pitches of ice index was developed as shown in Table 2.6.9. The ship speed distributions for the three service ships and escort icebreaker are summarized in Table 2.6.10 and Takie 2.6.11.
In the voyage simulations mentioned in chapter 3, IA, IB and IC are calculated for each segment in the selected route. Then the ship speed is calculated using the charts obtained here.
