Global climate changes decrease the ice extent across the Arctic Sea, i.e., the ice retreats northwards of the Russian north coast. This promotes an increase of commercial shipping in the Arctic, in addition to oil and gas resource exploitation activities. Arctic passages from Northern Europe to the Far East are economically appealing alternatives to existing sea-transportation routes, i.e. via the Suez Canal, due to up to 40% shortened distances and significant fuel savings. Furthermore, the reduction in sea ice increases the window for offshore operations and makes them feasible in formerly inaccessible areas.
The benefits of more profitable transport routes and explorations of natural resources come at the expense of significantly more demanding environmental conditions, which are also less well known, to which the ship has to comply to. The compliance concerns primarily a vessels ability to break ice while transiting.
The current icebreaking analysis is based on empirical knowledge and experience from relatively thin first-year ice, gained to a large extent in the Baltic Sea. As opposed to this, the availability of a direct simulation approach for an icebreaking vessel operating in various target ice conditions is of large commercial interest.
PRICE will address this interest and aims to develop a direct simulation approach for the prognosis of the hull load and icebreaking resistance. It brings together icebreaking ship designers from industry with academic experts from ice & structure mechanics, hydrodynamics & computational engineering as well as physical models and probabilistic methods in a joint collaborative effort. Unique to this project will be the synergy of these disciplines.
Direct simulations for an icebreaking vessel are of commercial interest, because extrapolating from small Baltic Sea vessels can be a major source of errors and the alternative to downscale, e.g. Russian polar icebreakers, will not result in economic concepts for merchant vessels.
Furthermore, a distinct winter navigation system is in place for the Baltic region, where the required ice performance is a function of economic constraints, because the vessels ice class is reflected in the port fees. For the arctic region, such system does not apply, but a considerable increase of transits is seen. A mission-based design method is thus required to ensure safe and economic performance in the Arctic (Ehlers et al. 2014). The shortage of direct simulation methods for the performance analysis in regions covered fully or partially by level ice, has also become an issue for design departments and consultants that focus on ice-class vessels for offshore and polar technologies.
Against the background of a lack of experience, common requests to design for competitive advantages and enhance the vessels performance under the aegis of decreasing time frames and financial restrictions might become business critical. This situation will be addressed by the strategic aim of the PRICE project to shift design practices towards efficient direct numerical simulation methods based upon first-principles.
Compared to the classical design approach – which combines class rules, experience and model tests – direct numerical methods offer some advantages, in particular when leaving the existing range of experience. Moreover, rule-based designs often display an economically disadvantageous level of conservatism in such cases (e.g. Lee, 2006). On the contrary, computational models promise the ability to evaluate more design options and operating conditions already during an early design phase.
Scientific aims of the project
PRICE scientifically aims at improvements of physical models and probabilistic approaches and their efficient combination in direct calculations of the icebreaking performance of ships. The computatio-nal framework refers to coupling a 3D flow solver to a modified contact-dynamic code. Key goals are:
Ship-ice-interaction is a fairly complex process. It depends on the ice thickness, the ice strength, the 3D hull geometry as well as the velocity of the ship and involves hydrodynamic aspects. Ship induced icebreaking is initiated by a localised crushing of the free ice edge. As the ship advances, the crushing forces increase parallel to the ice contact area. The ice sheet eventually deflects, also dynamically, and bending stresses promote a flexural failure at a certain breaking distance from the crushing region.
As opposed to model tests, computational approaches are not subjected to scale effects, which is deemed to be a major advantage. This is especially true, if the lack of scalability of model ice experiments and model ice itself is considered, see von Bock und Polach and Ehlers (2014). However, simulations of industrial problems usually have to compromise between accuracy and efficiency.
For this reason they often rely on physical models. As regards the ship-ice-interaction, the breaking pattern, loading & strength variation, environmental & cruise influence as well as hydrodynamic and geometric aspects are often covered by models that are occasionally supported by probabilistic features. In particular, the bending failure is neither fully understood nor accurately integrated into physical models of direct simulation tools. Without improving the employed models or progressively resolving the underlying physics at a moderate computational surplus, simulation-based icebreaking analysis tools will not be able to advance the industrial engineering capabilities.
(Coordinator) - Pella Sietas GmbH - Shipyard - Germany
The Pella Sietas GmbH results from a merger in April 2014 between the J.J. Sietas KG and Open JSC Pella from St. Petersburg, Russia. Pella is the leading company in the Russian tug building market. Tugs of Pella's new generation are successfully operating in all main Russian harbours. High quality and modern techniques of Pella's tugs were appreciated by customers from Norway, Italy and many other countries. Sietas is the oldest German ship yard and delivered worldwide the first container vessel “Bell Vanguard”. Many special purpose vessels like open-top containerships, heavy-lift vessels, tankers, ferries, self-unloading bulkers and an offshore installation vessel followed. The yard has a long experience in the design of specialised vessels fulfilling the demanding requirements from its worldwide customers. The new challenge for Pella Sietas results from increasing demand of ice-going vessels for the Arctic seaways. The first designs, which are currently developed, are a tug boat with a high ice class Arc 5, a rescue vessel with an ice class Arc 6 and an icebreaker design with the class notation Icebreaker 6 according to the Russian class rules.
Rolls Royce Marine AS - Blue Ocean Team - Norway
Rolls-Royce Marine has a world leading range of capabilities in the marine market, encompassing vessel design, the integration of complex systems and the supply and support of power and propulsion equipment. Rolls-Royce has a long experience in delivering mission-critical systems for offshore oil and gas rigs, offshore, merchant and naval vessels. Today the Rolls-Royce Marine product range is one of the broadest in the world. 70 of the world’s maritime forces and over 30,000 commercial vessels use Rolls-Royce equipment. With the ice-breakers Fennica and Nordica, Rolls-Royce are demonstrating the capability of being the frontiers of azimuthing thrusters with a high polar class, US-ARC. Furthermore three Rolls-Royce designed icebreakers has been delivered to Sakhalin Energy to support their offshore activities, showing the capabilities of a complete integrated system delivery including dynamic positioning in ice. As being an engineering company, Rolls-Royce is participating in various arctic technology studies together with other major player in the field. Through these studies the company has gathered a wide experience in model testing in arctic conditions as well as an excellent connection between model testing and full scale testing.
Hamburg University of Technology (TUHH M-8) - Institute for Fluid Dynamics and Ship Theory - Germany
The team has been / is involved in several activities in the area of computational engineering. About 15 national and international collaborative industrial research projects involving some 20 researchers are/were performed during the last 4 years. Emphasis is put on computational hydrodynamics (Greve et al. 2012; Manzke and Rung 2012; Manzke, Voss and Rung 2012), multibody/multi-continua hydrodynamics (Ulrich and Rung, 2012; Ulrich et al. 2013), flow-physics modelling (Yakubov et al. 2013, 2015), fluid-structure interaction (Gropengießer et al. 2012, 2014) or simulations based optimisation (Stück and Rung 2011, 2013; Stück, Kröger and Rung 2011) using mesh based or particle simulation strategies for high-performance computing systems (Yakubov et al. 2012). During the last three years, the team has developed a GPU-only free-surface flow procedure based upon the Lattice-Boltzmann Method (Janßen et al. 2012, 2015; Banari et al. 2014; Koliha et al.; 2014; Mierke et al. 2015). The latter is connected to a modified open source Physics Engine and has recently been supplemented by a simple ice-model.
Hamburg University of Technology (TUHH M-10) - Institute for Ship Structural Design and Analysis - Germany
The Institute for Ship Structural Design and Analysis (M-10) headed by Prof. Sören Ehlers currently consists of 35 employees ranging from academic to technical staff working in the vast strength laboratory. The institute is concerned with research on ships and offshore structures under service and extreme conditions using experimental, analytical and numerical analysis techniques. Prof. Ehlers has a long history on collision and impact simulations and experiments and within his institute he can test large to full-scale structures on a variety of testing rigs, which can be flexibly adjusted to research and development needs. The latest experimental facilities include besides resonance pulsators, a large 4 MN test rig, a wheel loading and friction rig and many more besides latest developments in low and very low temperature tests and structure-ice-interaction testing capabilities. The large 4 MN test rig will allow for large-scale structure ice experiments under controlled conditions by moving laboratory ice created in a cold room within a cylindrical container against rigid and deformable structures in a continuous crushing mode of the ice. The latter also contributes to the institute’s research on numerical modeling of ice mechanics and ice-structure interaction.
Norwegian University of Science and Technology (NTNU) - Department of Marine Technology - Norway
The Department of Marine Technology at NTNU has long experience in relation to analysis and design of ships and offshore structures. This also comprises testing both in the hydrodynamic and structural strength laboratories. Validation of calculation models has also extensively been performed by comparison with results from full-scale measurements. The department has a permanent staff of 25 professors in addition to a large support staff. Presently there are around 100 Phd and Postdoc employees which are engaged in a variety of research topics. A significant number of papers and Phd theses during the last decade have been concerned with operation and design of ships and offshore structures in Arctic regions. This also includes analysis and testing of ship hulls subjected to extreme loading caused by impact and collision with different types of ice features. Professor Leira has a long experience from reliability analysis applied to a variety of marine structures. This comprises statistical modeling of loads and structural strength properties as well as development of efficient and versatile calculation methods. Particular focus has been on statistical models related to ice loading on ship hulls based on full-scale strain measurements obtained from operation in the Svalbard region. Both extreme loading and fatigue accumulation due to repeated loading have been addressed. He is presently participating in a European Cost Action (started in 2015) which is concerned with “structural health monitoring” by performing processing of response measurements.