Statistical Estimation of Uncertainties Associated With Ship Operations in Fresh Water Ice

Cheemakurthy, Harsha (Royal Institute of Technology) | Zhang, Meng (Royal Institute of Technology) | Garme, Karl (Royal Institute of Technology) | Burman, Magnus (Royal Institute of Technology) | Ehlers, SÖren (Hamburg University of Technology) | von Bock und Polach, R. U. Franz (Hamburg University of Technology)

OnePetro 

ABSTRACT

Operational Time Window (OTW) and its confidence level are important for vessels operating in ice covered waters. This can be evaluated by quantifying all contributing factors in terms of their influence along with respective associated uncertainties. For a case study involving a barge operating in Lake Malaren, Sweden, five criteria are evaluated, and associated uncertainties are quantified using Variation Mode and Effect Analysis (VMEA) to give individual contribution towards overall uncertainty. Ship resistance due to ice and ice loads dominated over other criteria with highest contributions to uncertainty at 28% and 72% respectively.

INTRODUCTION

Inland Waterway Transportation (IWT) is a competitive alternative to road and rail transport, offering a sustainable and environment-friendly mode of transport (Wiegmans, Witte and Spit, 2015). It is also often the most economical inland transport mode with superior safety, high versatility, good reliability, low costs, high energy-efficiency, good carbon footprint, low noise levels and low infrastructure costs (Sihn, Pascher, Ott, Stein, Schumacher and Mascolo, 2015). In 2012, United Nations Economic Commission for Europe (UNECE) earmarked 29,172 km of Inland Waterways as E waterways (minimum dimensions of navigating vessels: 80.00 m × 9.50 m) in Europe. Sweden, a country characterized by its long coastline, lakes and inter connecting canals and rivers, is estimated to have IWW of 2052 km (CIA Statistics, 2018). This provides Swedish IWW with a huge potential to enhance existing transport network with IWT. However, due to geographical reasons, water bodies freeze for certain months during winter every year which impede usage of these water bodies.

Ships operating in ice are subjected to higher resistance and increased structural loads compared to open water. The difference can be attributed to ice properties like thickness, concentration, salinity, ambient temperature and its interaction with ship design variables like stem angle, flare angle (bow), hull strength etc. Several analytical, statistical, and numerical methods including class rules like Finnish-Swedish ice class regulations (FSICR) have been introduced in the past for estimating ship resistance and structural response in ice covered waters. However, these methods and existing research has been primarily focused on addressing sea water ice whose properties are very different from fresh water ice and direct application of these methods for prediction of ship performance in inland waterways is not accurate and subjected to associated uncertainty.