抄録
A recently proposed Distributed Mass/Discrete Floe model (DMDF model) is a model for practical computations of pack ice motion. The floes are divided into bunches, in which they are assumed to be distributed uniformly. As a result, larger number of floes can be treated in comparison with discrete element models. The ice interaction force is formulated from the momentum conservation in the collisions of floes in a bunch and between the bunches. The movement of floes is calculated in combination with water flow using a multi-layer model to express the surface flow more accurately. This paper describes an improved disk floe version. In a circulation water channel, drift tests of physical model floes were performed in order to investigate characteristics of their motion and interaction with the structure. The results are summarized as follows :
The floe motion near the structure depends on the floe shape. Disk floes show a lateral motion in front of the structure. They flow out from both sides. As a result, the number of the floes is front of the structure decreases with time. Rectangle floes, however, have no motion in front of the structure. The number of the floes in front of the structure remains constant with respect to time. These experiments indicate that when the motion of pack ice is simulated around a structure, it is important to choose the floe shape. The disk floe motion and the rectangle floe motion can be regarded as the two extreme cases of real pack ice motions. An actual pack ice motion may be between these two extreme cases.
Two computations using DMDF model were made. Simulation results were compared with the circulating water channel experiments and the forecast of the operational model of Environment Canada. The DMDF predicted the circulating water channel drift tests quite closely. The DMDF results also compared quite well with the computations at the Environment Canada.
