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Marine icing due to freezing sea spray has been attributed to many safety incidences. Prediction of sea spray icing is necessary for operational safety, design optimization, and structural health. In general, lack of detailed full-scale measurements due to the complexity and costs make validation difficult. The next best option is that of controlled laboratory experiments. The current study is the first study in the field of sea spray icing that investigates the use of new data science technologies like machine learning and feature engineering for the prediction of sea spray icing based on data collected from controlled laboratory experiments. A new prediction model dubbed "Spice" is proposed. Spice is designed "bottom-up" from experimentally collected data, and thus, if the input variables are accurately known, it could be said to be highly accurate within the tested range compared to existing theoretical models. Results from the current study show promising trends; however, more experiments are suggested for increasing the range of confident predictions and reducing the skewness of the training data. Results from spice are compared with five existing models and give icing rates in various conditions in the middle of the spectrum of the other models. It is discussed how validation from two existing full-scale icing measurements from literature proves to be challenging, and more detailed measurements are suggested for the purpose of validation. [ABSTRACT FROM AUTHOR]

Sea spray icing on ships and marine structures depends on a complex correlation between metocean parameters and vessel characteristics. Sea spray icing rates have mostly been investigated and given as a function of general metocean parameters. The existing models suffer from the lack of experimental data. More experimental data are required for better prediction models and understanding of the icing process. This article presents results from a comprehensive cold laboratory study of the dependence and trends of sea spray icing rates related to eight parameters. Experiments were performed simulating sea spray from a nozzle toward a vertical surface in the freezing environment. This study presents 20 unique tests structured into eight experiments, each of which focuses on change in icing rates due to one independent variable. Results showed that the sea spray rate dependence of the investigated parameters complies with the existing knowledge; however, preliminary analysis points out various unintentional covariates for most experiments that call for further investigations. This is the greatest number of variables tested in one set of experiments to date and serves as valuable sea spray icing data experimental data--a limitation for the evaluation of previous models that pointed out the lack of enough icing measurements in this field of research. [ABSTRACT FROM AUTHOR]

For ships navigating in ice floe fields, ship-ice-wave interactions may affect ship performance and ice impact forces. This paper presents an approach to evaluate the cross-coupling added mass and hydrodynamic damping between a passing ship and a free-floating small/medium size ice floe based on the boundary element method (BEM). The influences of added mass and hydrodynamic damping are explored for different wave frequencies and headings. Results are presented for a regular waves scenario whereby a tanker progressing at a slow speed is passing by a free-floating ice floe modeled as a round disk. Radiation and diffraction potentials of the interacting floating bodies are linearly superimposed to reflect the influence of hydromechanical coupling on responses. Parametric analysis of response amplitude operators (RAOs) indicates that the cross-coupling terms of added mass and hydrodynamic damping are of the same order of magnitude as those of the ice floe but smaller by one or two orders of magnitude than those of the ship. It is concluded that hydrodynamic interactions primarily influence the motions of the ice floe and are significant attributes in terms of suitably idealizing ship-ice system dynamics. [ABSTRACT FROM AUTHOR]

Global warming has extensively transformed Arctic sea ice from continuous level-ice coverage to unconsolidated ice floe fields. Whilst the ice floes have a mixture of different sizes and their locations are randomly distributed, contemporary computational models lack effective methods to generate floe fields with such a natural pattern. This work introduces two original tools that can generate realistic ice floe fields for computational models. They are a sequential generator that sequentially handles ice floes one by one, and a genetic generator based upon a genetic algorithm. Demonstration of the tools is given, presenting samples of generating various shapes of floes and arbitrary mixtures of different shapes. Furthermore, an example is provided that combines the generated floe field with computational work modeling a ship transiting in ice floes. In addition, the source code of the tools is sharable to the public. [ABSTRACT FROM AUTHOR]

Design life of offshore structures is in general in the 20-to 30-year range, with some cases going up to 50 years. Fatigue is one of the major design criteria for such structures. Climate change may affect the fatigue life of offshore structures, it would be necessary to update the design procedures to take into account climate change effects on structural performance. This paper aims to investigate the impact of climate change in the long-term fatigue life of offshore structures due to wave loading. For this purpose, available environmental conditions for two locations (South East Brazilian Coast and North Atlantic Ocean) generated by the HadGEM-2S global climate model, considering representative concentration pathway (RCP) 4.5 and RCP 8.5 future scenarios and the historical (past) scenarios are considered. The assessment in both locations is performed for two structural models: an idealized stress spectrum for a generic fatigue hot-spot and a steel lazy wave riser (SLWR) connected to a floating production storage and offloading (FPSO). Fatigue life is estimated using the S-N curve approach. Results show that the impact on the fatigue life depends on the structure dynamic characteristics, on the geographic location and mainly on the greenhouse emission scenario. In general, for the Brazilian location, when compared to the historical scenario, most of the future scenarios lead to slightly higher fatigue damages (lower fatigue lives). On the other hand, for the North Atlantic location, there is not a clear trend for future climate change scenarios. [ABSTRACT FROM AUTHOR]

This paper presents a finite element model for the simulation of ice-structure interaction problems, which are dominated by crushing. The failure mode of ice depends significantly on the strain rate. At low strain rates, the ice behaves ductile, whereas at high strain rates it reacts in brittle mode. This paper focuses on the brittle mode, which is the dominating mode for ship-ice interactions. A multitude of numerical approaches for the simulation of ice can be found in the literature. Nevertheless, the literature approaches do not seem suitable for the simulation of continuous ice-structure interaction processes at low and high confinement ratios in brittle mode. Therefore, this paper seeks to simulate the ice-structure interaction with the finite element method (FEM). The objective of the here introduced Mohr-Coulomb Nodal Split (MCNS) model is to represent the essential material behavior of ice in an efficient formulation. To preserve mass and energy as much as possible, the node splitting technique is applied, instead of the frequently used element erosion technique. The intention of the presented model is not to reproduce individual cracks with high accuracy, because this is not possible with a reasonable element size, due to the large number of crack fronts forming during the ice-structure interaction process. To validate the findings of the model, the simulated maximum ice forces and contact pressures are compared with ice extrusion and double pendulum tests. During validation, the MCNS model shows a very good agreement with these experimental values. [ABSTRACT FROM AUTHOR]

As part of the Mechanics of Ice Rubble project, recent experiments have been carried out to study the strength and failure behavior of ice rubble beams and the freeze bonds that form between individual ice blocks. In this study, we present results obtained from a newly developed model for the three-dimensional (3D) discrete element modeling (DEM) open-source code LIGGGHTS. The ice model contains normal and shear springs that operate between neighboring particles which are bonded or that overlap due to compressional stresses. Energy dissipation is accounted for by using a viscous damping model. Using this DEM model, medium-scale freshwater ice rubble punch tests have been simulated. Rubble specimens were generated by "raining" individual DEM ice pieces into a rectangular form and compacting the rubble mass to achieve the target porosity. Before the compacting pressure was removed, bonds between contacting blocks were introduced with parameter values based on representative freeze bond experiments. The rubble beam was then deformed by pushing a platen vertically downward through the center of the beam until failure occurred. Two types of block size and shapes have been simulated: cuboid blocks generated based on the size distribution of the actual rubble, and rubble blocks generated by image processing of actual blocks of broken ice used in the comparison experiments. The mechanism of flexural rubble failure for both cuboid block [s4.2] simulations and empirical block [s4.3] simulations is in line with experimental results; however, the empirical block simulations provide a significantly better estimation of the failure force. [ABSTRACT FROM AUTHOR]

It is well known that material properties undergo significant changes with temperature. In order to meet extreme environmental requirements for ships and offshore structures operating in Arctic regions, the effect of temperature on material behavior needs to be considered. In recent studies, significantly higher fatigue strength was observed for base materials and welded joints in comparison to room temperature. Fatigue strength increased even for temperatures far below the allowed service temperature based on fracture toughness results; however, sub-zero temperatures fatigue data are scarce and the effects of steel strength and welding type on fatigue strength changes are unknown. Material selection for ships and offshore structures is typically based on empirical Charpy and fracture toughness relations at the design temperature, minus a safety margin. Thus, this study presents material test results including fatigue tests of butt-welded joints, tensile test, and Charpy impact toughness tests at room and sub-zero temperatures of different structural steel types. Additionally, the effect of welding techniques and steel strength are discussed. The results can be used to extend design approaches for ships and offshore structures subject to sub-zero temperatures and to improve material selection for ships and offshore structures operating in Arctic regions. [ABSTRACT FROM AUTHOR]

This paper presents a state-of-the-art digital twin of a hydraulic actuated winch that is used for heave compensation in offshore applications. The digital twin is used as part of a larger simulation model that involves all necessary components to perform lift planning and, subsequently, determine the corresponding weather window. The winch simulation model is described and verified by means of full-scale measurements. In addition, a set of acceptance criteria are presented that should be used whenever verifying digital twins of heave compensating winches that are to be used for lift planning. [ABSTRACT FROM AUTHOR]

A simplified analysis method was developed to evaluate the fatigue damage of an ice-going ship under broken ice conditions. The ice resistance, which is available in the early design stages of an ice-going vessel, and the hull form information were used to estimate the local ice load acting on the outer-shell of the ship. The local ice load was applied to a finite element analysis model, and the Weibull parameters of the local stress range at the target fatigue point were derived. Finally, the fatigue damage was evaluated by applying the S-N curve and Palmgren-Miner rule. To verify the proposed method, numerical analyses using the direct approach, which takes into account the detailed interaction model among the fluid, structure, and ice, were performed under the same conditions. Fatigue analyses of the Baltic Sea for actual ice conditions were performed to check the validity and applicability of the proposed method, and the resulting fatigue damage was compared with that obtained by the classification society's recommended practice. [ABSTRACT FROM AUTHOR]

This paper investigates the question of the existence of nonlinear wave-ice interaction with the focus on nonlinear wave propagation and dispersion of waves. The scope of this investigation is to provide a better understanding of ice and wave conditions required to observe nonlinear wave effects under level ice. Direct numerical simulations of nonlinear waves in solid ice are performed within the weakly nonlinear Schrödinger equation (NLSE) framework, using the theoretical findings from Liu and Mollo-Christensen's 1988 paper. Systematic variations of wave and ice parameters address the impact of the mechanical ice properties and ice thickness on traveling waves of certain wave lengths. The impacts of parameter characteristics on nonlinear focusing and wave dynamics, as well as possible constraints regarding physical consistency, are discussed. It is presented that nonlinear focusing in level ice occurs theoretically. Hereby, distinctive areas of validity with respect to nonlinear wave focusing are identified within the parameter study, which strongly depends on the material properties of the level ice. The results obtained in the parameter study are subsequently used to investigate wave focusing under level ice. Therefore, an exact solution of the NLSE, the Peregrine breather, is utilized. The analytical solution for level ice is compared to the open water solution and accompanied by direct numerical simulations. These investigations show that nonlinear wave focusing can be predicted under level ice for certain parameters. In addition, the agreement of the direct simulations and the analytic solution verifies the numerical approach for nonlinear waves in solid ice. [ABSTRACT FROM AUTHOR]