Efficient hull design for ice conditions in inland waterways
Time: Thu 2022-09-15 10.00
Location: F3, Lindstedtsvägen 26 & 28, Stockholm
Subject area: Vehicle and Maritime Engineering
Doctoral student: Meng Zhang , Farkostteknik och Solidmekanik
Opponent: Professor Pentti Kujala, Aalto university
Supervisor: Karl Garme, Farkostteknik och Solidmekanik; Magnus Burman, Farkostteknik och Solidmekanik
With increasing interest in utilizing the inland waterways (IWW) in European countries, the design of IWW vessels gains attention both from a transport efficiency and an emission control point of view. Usually, IWW ships are designed without ice operation concerns and are structurally weaker than ships designed according to ice-class notifications from the classification societies. It poses a potential danger for countries with long winter seasons and frozen waterways. Designing such ships requires particular concerns since there are no strict requirements regarding ice-class notifications for IWW ships. Among all the design issues, the primary challenge is to estimate the ship resistance and impact load on the ship hull structure.
To consolidate the design challenges for IWW ice-going ships, Lake Mälaren is selected. The mechanical properties of ice have a significant influence on the ice load. Ice conditions, e.g. ice type and concentration, and ice data, e.g. thickness and flexural strength, are extracted and analyzed for the ice load estimation. Ice characteristics are studied based on empirical formulae and calibrated by reference data.
Determination of the ice impact load is the first vital step in designing a lightweight structure. A deterministic approach and a probabilistic approach are used to predict the ice loads. The Finnish Swedish Ice Class Rule (FSICR) is the deterministic approach used for the first-year freshwater ice conditions. The probabilistic approach includes a probabilistic and a numerical method. The probabilistic method simplifies the ice pressure in relation to the contact area between the ice and the ship hull. The numerical method investigates the idealized ship-ice impact model regarding the ice failure process, ice conditions, and ship geometry. Given the impact load, a lightweight panel is designed, and it saves almost 83.5% weight compared to a stiffened steel panel. This is achieved by using a sandwich structure with a composite face and PVC core.
Ship resistance in ice-covered water plays a significant role in assessing the operational scenario. It is essential for ship owners and operators to evaluate ship economics. In order to estimate ship resistance in ice-covered water, an Artificial Neural Network (ANN) model is developed by using suitable ship and ice parameters. A statistical model is designed to account for the most important ship operation variables, i.e. ship speed and ice thickness. Combined, the two models provide a very promising way to estimate a ship's Operation Time Window.