Abstract

This paper investigates the influence of sea disturbance on towing system behavior with the means of numerical modelling. The obtained results showed wide possibilities of proposed numerical models for investigation of the nonstationary process of iceberg towing by single tow line (rope). Estimations of maximum forces are important characteristics for design of towing systems, implementation of which can enhance efficiency and safety of the iceberg management operations.

Introduction

Drifting icebergs may threaten offshore structures, vessels and suspend marine operations in a number of Arctic and Antarctic regions. Multifunctional ice breaking supply vessels are usually used to eliminate ice threats to offshore constructions by physical impact on the ice cover and icebergs. These vessels tow icebergs and their debris away. Technical success of iceberg towing operation is directly related to the reliability of the towing system, which is a subject to significant dynamic loads. The planning of iceberg towing operations involves mathematical models which are based on the very few available results of field experiments and basin modelling.

At present, there are no universal mathematical models for the process under consideration. This absence is caused by uniqueness of each ice feature characteristics, diversity of marine and weather conditions. That is why it is necessary to take into account unsteadiness and high degree of non-linear nature of the dynamic process.

Calculation models of the iceberg towing process is important for engineering applications and safety of navigation. In works (C-CORE, 2004; Rudkin et al., 2005; Young et al., 2006) authors investigate the relationship between iceberg stability and towing parameters such as tow force, point of application, acceleration and tow speed. Recently a number of publications were devoted to the problem of models development (Eik et al., 2010; Yulmetov et al., 2016; Yulmetov et al., 2017). These works describe numerical models based on analytical dependency of mechanics and reveal significant difficulties in the modelling of iceberg towing process and calculation of non-linear dynamic effects in the "vessel- tow line-iceberg" system.

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