Detailed simulation logic
Following the stepwise logic used in the model,
1. Set initial speed
this section descibes how the simulated ship's base
based on ice conditions.
speed is first established and then adjusted for the
current environmental conditions. Figure 11 shows
a generalized flowchart of steps completed at the
2. Get winds.
start of each segment of the simulation procedure.
We define a simulation segment as any portion of
a transit for which all variables remain constant.
Variables are re-evaluated according to steps in
3. Adjust speed
for waves.
the shaded box every 8 transit hours, which is the
longest period of time spanned by a single seg-
ment. Segments may be shorter if, for instance, the
4. Adjust speed
simulation clock indicates that the sun rises or sets
for visibility factors.
within an 8-hr period, or if the ship reaches a data
point or decision node before a full 8-hr segment
is completed. The objective of the logic outlined in
5. Add currents.
Figure 11 is twofold: a) to establish the steaming
speed that the cargo vessel will maintain during
the entire transit segment that is about to begin,
6. Update time
and, once speed has been established, b) to keep
and distance travelled.
track of ship position and distance traveled so that
simulation variables (heading, ice, wind, fog, cur-
rents, etc.) can be updated when the next data or
7. Save
segment statistics.
decision node is reached.
Ship speed is considered as a function of four
groups of variables: a) ice conditions, b) sea state,
c) fog, snowstorms, icing, and darkness as they
Figure 11. Simplified flowchart of steps
affect visibility and maneuvering ability, and d)
performed during each simulation seg-
ocean currents. Ice conditions determine the ini-
ment.
tial speed, which subsequently is adjusted down-
ward if warranted by environmental factors such
as wind, waves, and conditions that degrade vis-
speed that the vessel can maintain, but also
ibility and maneuverability.
whether escort by an Arktika-class icebreaker is
needed. The initial speed of the cargo ship is es-
Set initial speed for ice conditions (step 1)
tablished by selecting values for sea-ice concen-
We established an initial speed for the cargo
tration and thickness using the MC algorithm.
vessel by evaluating sea ice conditions. Ice condi-
Table 10 gives initial speed as a function of ice
tions not only determine the maximum forward
Table 10. Base ship speed initialized as a function of sea-ice thickness and
concentration. Shaded cells indicate conditions that trigger icebreaker escort.
Ice thickness (cm)
Ice free
<120
120180
180240
>240
Ice free
Full speed*
Ice
<30
8
8
7
6
concentration
3060
Full
8
8
7
6
(%)
6080
speed*
6
10
10
10
80100
8
6
6
4
*Full speed values: a) Noril'sk (containerized cargo): 17.0 kn; b) Lunni (liquid bulk cargo):
14.5 kn; Strekalovsky (dry bulk cargo): 15.2 kn.
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