Simulation of Ice Management Operations

Abstract

InthecontextofincreasingindustrialandeconomicalactivitiesintheArcticOcean, thepresent work focuses on physical ice management, the set of techniques used to reduce the threats from potentially hazardous or restrictive ice conditions relatively to a platform or structure. The objective is to develop a MatLab simulation tool for ice management operations. Accordingtoseveralinputparameters,thesimulationcodeisabletopredictanoperationscenario, generate a visualization of the operation and produce post-processed results. Software structure is developed in the following. First, the relevant parameters of the operating conditions are defined: ice thickness, drift velocity, icebreaking vessel power, etc. and maximum acceptable size of the broken floes. In level ice, the resistance is estimated thanks to the semi-empirical theory of Lindqvist (1989). The simulation tool determines then the equilibrium point of the icebreaker, i.e. the ship velocity such that propeller thrust equals ice resistance. For the resistance in ridges, a dynamic simulation model is developed from the theories of Slettebø & Ueland (2010) and Ehle (2011). Another part of the tool defines the turning ability of the icebreaking vessel(s). The code is based on a theoretical approach of the turning maneuver, coupled with the Lindqvist (1989) resistance estimation method in linear motion. In order to manage the ice updrift a structure to defend, a management strategy (linear, sector, circular,...) is selected according to the actual ice configuration : drift velocity, varying direction, etc. The area within the icebreaking vessel(s) will work is then defined from the dimensions of the protected structure, but also from the drift speed and directional variability. The trajectory of each vessel is calculated and an animation of the ice management operations is obtained, including drift motion of the ice pieces. If the requested ice management appears to be impossible, the software gives the reasons and suggests solutions (requested icebreaking power,...). From the resulting broken ice field, the software measures the corresponding floe size, mass and momentum distributions that can then be used to compare the different management techniques, regards to the ice conditions and available icebreaking fleet. Validation is performed through comparisons with full scale or model scale results. Thanks to the large database of experimental results of the Hamburg Ship Model Basin, several parameters of the calculation can be adjusted with values from similar vessels/maneuvers in order to improve the accuracy of the simulation. The report ends with some conclusions and suggests further work to be performed in order to enhance the model.