After the analysis of the environmental data supplied WP2,the data (mean-standard deviation (low value), mean, mean + standard deviation (high value)) shown in the Table 2.6.5 were selected as the basic environmental data.

　

Table 2.6.5 Basic environmental data

　

Finally, the total of 3⁵=243 combinations of environmental data were produced from the basic environmental data. However the data combinations under the following conditions were cut out.

・The combination of data in which the total ice concentration ＞10

・ The combination of environmental data which does not exist in the real situation (for example, data in which mean ice thickness is 27 cm, the mean sail height is 149cm or 94cm, and the ridge density is 27.7/km.)

　

The combination data and the ice index obtained by the method that we discussed chapter 2.6.2 were presented in Tables in Appendix B. When the ice index was calculated, I_C is not considered because its value is very small compared with I_A or I_B.

　

Ship speed distribution for each type of vessels

Using the code NEWSIM2, the ship speed distribution was obtained for three service ships and Arctica type escort icebreaker. As the data of floe size (para.12), the average data (12.2 m) was used. The input data of the ships are shown in Table 2.6.6. The ice multipliers for TYPE A and CAC1 in Table 2.6.3 were applied for the three icebrcaking cargo ships and the escort icebreaker respectively. The combination data in the Appendix B were used as the environmental data.

Then, the ship speed was corrected by both maneuvering factor and ice compression effect, as described below.

　

2.6.4 Speed correction factors

Correction of ship speed by maneuvering factor in severe ice condition

On the navigation in the ice covered waters, a master of the icebreaking cargo ship tends to avoid severe ice condition and chooses open leads. The decision of the operation is made depending on the condition of ice thickness and concentration. If he avoids the severe ice condition, the navigation distance becomes longer, although the ship speed appears to be increased. Consequently, the transit time in one segment tends to be shorten in less concentrated ice. C_ma, is defined as the adjust parameter for maneuvering referring to the model porposed by the CRREL (Mulherin, 1996) as shown in the Table 2.6.7. The maneuvering effect is 3-5%, of the ship speed. Here, the adjust parameter C_ma is multiplied to the ship speed from NEWSIM2.

　

Table 2.6.7. Adjust parameter Cma for the maneuvering

前ページ　　　目次へ　　　次ページ