Propeller-ice interaction

In the project HealthProp (MARTera co-fund scheme, H2020) we seek to model the ice failure against a propeller blade. The project is based of a series of experiments with increasing complexity that are modeled in the process. The image shows the simulation of an experiment where a balde edge cuts a cylindrical ice specimen. The main goal of HealthProp is to develop a digital twin platform - by combining intelligent sensors, data acquisition systems and fault detection algorithms through physical and data-driven models in the cloud - towards monitoring the propulsion system and drive line of ships in Arctic and Antarctic operations, with the aim to improve the system reliability and increase the operational safety in harsh environmental conditions. The TUHH develops in Healthprop a new ice load model for propellers. The research is a combination of large scale experiments an simulations. With the results in our work packages we seek to predict the ice loading on a propeller more accurately and therewith the longterm impact regaring fatigue and wear of components. The project is part of MarTERA - an ERA-NET Cofund scheme of Horizon 2020 of the European Commission - and the Research Council of Norway (Project no. 311502), the Federal Ministry for Economic Affairs and Climate Action of Germany (Project no. 03SX519B), and Department of Science and Technology of South Africa, through the HealthProp project.

– Jonas Behnen (former researcher), Angelo Böhm (researcher), Franz von Bock und Polach (PI)

Non-linear wave-ice interaction

During a test campaign in the Ice Tank of the Hamburg Ship Model Basin (HSVA), we investigated the damping of regular waves in non broken model ice. Both active ultra sonic and passive video tracking sensors were used to detect the properties of the waves. By distributing narrow spaced passive sensors over a five meter distance on the solid ice sheet, it was able to reconstruct the wave number and to derive the dispersion relation in ice. In the left figure the exponential decay of the wave amplitude for the different wave numbers is shown. The decay represent the damping of the waves due to the ice sheet and corresponds well to other research. Furthermore, the trend of increasing exponential coefficient with increasing wave number is visible by comparing the four figures which indicate that higher wave frequencies are stronger damped by the solid ice sheet. Hartmann, M. C. N., von Bock und Polach, R. U. and Klein, M. ‘Damping of Regular Waves in Model Ice’, 2020, ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. Research project "Nonlinear wave-ice-interaction" funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)

– Moritz Hartmann, Franz von Bock und Polach, Marco Klein (PI)

Large-scale Ice-Structure Interaction Tests

Ice loads pose a significant hazard to ship and offshore structures. Unlike in automotive industry, for example, full-scale collision tests of ships are hardly possible. In order to be able to investigat critical ice-induced deformations of real ship structures in a laboratory envirement the ice extrusion test was developed at the Instiute of Ship Structural Design and Analysis at Hamburg University of Technology. During the experiment, an ice specimen is pushed out of a confining pipe (orange) against the considered test structure. In previous campaigns, both quasi-rigid and ice-strengthed panels, such as those commonly used for ships in the Baltic Sea, were investigated. Plastic deformations of the panel up to 87 mm were achieved at 4 mm/sec cylinder velocity. The experimental data are now available to improve the understanding of ice-structure interaction and for the development of new or the enhancement of existing numerical models to enabable reliable simulatins of ice loads for e.g. risks accessment, operational guidance or rule development.

– Hauke Herrnring

What role does the ice shape play in ship collisions scenarios with icebergs or ice floes?

In our project IceShape we investigate experimentally and numerically ice-structure interaction scenarios with different shaped ice specimen. This serves to find the potentially most dangerous impact case in ship-ice collision scenarios. To analyze the influence of different geometry parameters we conducted experiments in model scale with 17 different ice shapes. Therefore two different test rigs were utilized to be able to test a high range of interaction velocities of 10 to 2000 mm/s. In both test setups the ice was crushed by a steel plate, that was in one case hydraulically driven and in the other case released from a predefined drop height and fell vertically guided onto the specimen. The force acting in vertical direction was recorded by load cells and the displacement of the steel plate was measured by a displacement transducer. A comparision of the maximum measured forces showed a high dependency on the ice geometry. Ice geometries with a large parallel contact area to the steel plate (like a cylinder) showed the highest forces with values up to over 300 kN. Whereas ice specimen with no or small parallel contact areas (like a cone or dome) showed very low forces with values below 50 kN. The experiments showed further that even a inclination of 1° between the contact area of the ice and steel plate leads to a drop in max. load of over 50%. With respect to the interaction velocity is was found, that low velocities between 10 and 100 mm/s lead to similar results. Interaction velocity of 2000 mm/s lead, depending on the ice shape, to loads that are 70% higher compared to lower interaction velocities. In a next step the experimental data will serve as a database to validate the numerical simulation and further develope it to be able to apply it to full-scale ship-ice collision scenarios.

– Franciska Müller