Investigations on the effect of friction on the total ice resistance in brash ice conditions

Abstract

The maritime industry is an ever evolving one. It has felt the presence in the change in trends and demands of globalization. Along with it new routes emerge which let us venture into unknown paths. Although the sailing time in ice is limited, merchant ships often need significant extra powering to meet the ice class requirements. It is important to study the resistance of ships in brash ice as it helps us to determine the required engine power of the ship and helps us to reduce the fuel consumption leading to reduced greenhouse gas emissions. In Arctic regions, waterways often become covered and congested with relatively small-sized ice rubble, known as brash ice. Brash ice is composed of accumulated ice fragments, primarily the debris produced when the ice cover over a channel is broken by a ship passing through the channel. With each transit, more brash ice is produced from the ice cover regrown from the channel. Though properties and growth has been studied before, there is a need for further study on the frictional effects in brash ice conditions. To understand brash ice conditions better, HSVA focuses on the study of the effect of friction on the total ice resistance. The portion of different resistance components in brash ice are studied along with the effects. For the same, model test results are evaluated with different friction coefficients. In this current thesis, literature study of the limited resources on ice resistance in brash ice conditions are presented. This would help us to understand the past research on similar topic. Along with that model scale test results along with its associated results are also exhibited. The ship were initially grouped on the basis of the dimensional parameters. Then parameters of the same have been varied and the effects on the relative resistance that pertains to a certain group is noted. Mathematical models are also followed using the same test values to evaluate the same and hope to emerge into a converging result. The mathematical models have been processed by using empirical relations as well as totally analytical derivations. One of the mathematical model stated as Dobrodeev model has down the total resistance into various sub groups i.e. frictional resistance, momentum resistance etc. Every sub group has been evaluated based on different criteria's and then summed up to derive the total resistance. Riska model as followed has empirical formulas and derived constants from earlier studies of other vessels. The Mellor model is totally analytical method which is primarily based on the hull shape. This all is done to improve our understanding the effect of friction on the total resistance in brash ice conditions