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The issue of thermodynamic modeling of brash ice accumulation in an ice channel is considered. The determining influence of the fill factor (or porosity) on the calculation results has been revealed. Based on theoretical assumptions and field data, an approximation of the fill factor vertical distribution has been proposed. Using the thermodynamic model, test calculations of brash ice accumulation have been carried out taking into account the proposed approximation. The calculation results have demonstrated a clear effect of nonlinearity in the rate of brash ice accumulation. Some recommendations are given for taking this fact into account in modeling the interaction in the ship–brash ice system. [ABSTRACT FROM AUTHOR]

Polar transport ships frequently traverse in the brash ice channel opened by icebreakers. Although the substantial ice resistance caused by direct collisions with the level ice is avoided, the hull still encounters collisions with the brash ice, leading to periodic damage and exacerbating the fatigue issues of the hull structure. To address the fatigue challenges faced by ships sailing in the brash ice channels, this paper proposes an ice-induced fatigue damage assessment method based on the CFD-DEM-FEM. Referring to the brash ice model test conducted at the Hamburg Ship Model Basin (HSVA), a discrete element ice model and a numerical brash ice tank are established using the CFD-DEM coupling method. The simulated ship-ice interaction is compared with HSVA's experimental results to validate the reliability of the numerical brash ice tank and ice load. The ice load time history resulting from the ship-brash ice collision is applied to the hull, and the hot spot stress time history under each fatigue subcondition is calculated using the FEM. The improved rain-flow counting method is employed to determine the stress level of the hot spot stress time history, and the S-N curve method based on the linear cumulative damage criterion is used to calculate the total fatigue damage of hot spots. Finally, the results of the proposed method are compared with those of the LR method. This study can serve as a valuable reference for the ice-induced fatigue assessment of ships navigating in brash ice channels. [ABSTRACT FROM AUTHOR]

The urgency of brash ice study is growing in connection with intensive shipping in fast ice zone of freezing seas as well as inland waterways. In addition, an important incentive for such studies is the design and construction of port infrastructure in these water areas. The review shows that the main directions of research refer to three main topics. 1) Investigation of morphometrical brash ice characteristics in navigable channels and harbors, their variability under ambient factors. The most well-studied morphometrical parameters of brash ice are relative channel thickness and its distribution over channel width. Size distribution details about brash ice floes are of great interest for researchers. 2) Investigation of porosity and mechanical properties of brash ice as a granular material taking account of freezing between individual ice blocks. In many respects, these parameters determine the pattern of brash ice interaction with ships and the possibility of their movement. 3) Description of consolidated layer formation in brash ice and refinement of predictions for brash ice growth in the water area under consideration depending on the intensity of ship traffic and the number of degree-days with negative temperatures over the time interval between ship passages. Large attention is given to new methods of studies including full-scale and laboratory experiments, as well as the use of ice basins for this purpose, with a brief review of thermal methods for brash ice management. The paper formulates some of the problems yet to solved, which require extra studies.

The thickness and properties of brash ice are usually compared with the properties of the surrounding level ice. The differences between these ice types are important to understand since the consolidated brash ice layer is typically assumed to have the same properties as level ice. Therefore, significant effort in the measurement campaign during the winters of 2020–2021, 2021–2022, and 2023 was made to develop a better understanding of the full-scale brash ice channel development. The channels were located near the shore in the Bay of Bothnia, Luleå, Sweden. The main parameters investigated were the snow, slush, and total ice thicknesses, including ice formed from freezing water and from freezing slush as well as the ice microstructure and strength. To our knowledge, this is the first paper to report the influence of snow in brash ice channels. It was observed that a significant amount of snow covered the brash ice channels between the ship passages. After each ship passage, the snow was submerged and formed slush-filled voids, which thereafter transformed into snow ice (SI) clusters frozen together with columnar ice. The SI content in the brash ice and side ridges was estimated from image analyses. The analyses showed that the snow ice content was 73% in level ice in the vicinity of the ship channel, 58% in the side ridges of the channel, and 21% in the middle of the test channel, whereas in the main channel, the SI contents were 54%, 43%, and 41% in each location, respectively. [ABSTRACT FROM AUTHOR]

Formation navigation in brash ice channels is increasingly utilized by merchant vessels in the Arctic and Baltic Sea, offering benefits such as improved efficiency and reduced carbon emissions. However, ship–ship interference poses a significant challenge to this method, impacting resistance performance. This paper presents full-scale simulations using the CFD–DEM coupling method in brash ice channels, which is validated by comparing simulation results with ice tank measurements. By varying the distance between two ships from 0.05 to 5 ship lengths, ship–ship interference in full-scale brash ice channels is analyzed using the CFD–DEM coupling strategy. The study examines hydrodynamic and ship–ice interactions, ice resistance effects, and simulation results. It is found that ship-to-ship distance significantly influences the velocity field, dynamic pressure distribution on the hull, and hydrodynamic interaction forces. Distances less than one ship length result in increased water resistance for the forward ship and decreased resistance for the rear ship. The forward ship demonstrates favorable interference with the ice accumulation of the rear ship. When distances are less than two ship lengths, the ice resistance of the forward ship remains mostly unaffected, while the ice resistance of the rear ship decreases as the distance decreases. These insights enhance our understanding of ship–ship interference in formation navigation, aiding in the optimization of brash ice channel navigation strategies. [ABSTRACT FROM AUTHOR]

Main engine power prediction is important for polar ships operating in brash ice channels, which is one of the most important concerns of shipowners. Self-propulsion simulation is an efficient method to predict the developed power. At present, such models as the discretized propeller model (DPM) and the body force model (BFM) are used for self-propulsion simulation. However, these models are often limited to open water. There is little research on self-propulsion calculations in ice-infested water. This paper presents the BFM to carry out self-propulsion simulations in a brash ice channel. Research on simulation strategy for open water performance based on the BFM is carried out. Ship–ice–water interactions are simulated using computational fluid dynamics-discrete element method (CFD-DEM) coupling method. Both loaded and ballast conditions are considered in the model-scale self-propulsion simulations. Numerical results based on the BFM are compared with the simulation results based on the DPM, as well as model test results. Ship–propeller–ice interactions and propeller suction effects are also compared with photographs taken at an ice tank test. The results show that the differences of the developed power based on the BFM for both loaded and ballast conditions are 8.94% and 15.25%, respectively. The prediction accuracies of the developed power based on the BFM for both loaded and ballast conditions are 1.56% and 7.01%, respectively; lower than those based on the DPM. However, the computation efficiency based on the BFM is 12 times higher than that based on the DPM. To conclude, the proposed BFM could be used as an effective means to calculate the developed power and to evaluate the trend of hull-line optimization at the development stage.

Formation navigation in brash ice channels is increasingly utilized by merchant vessels in the Arctic and Baltic Sea, offering benefits such as improved efficiency and reduced carbon emissions. However, ship–ship interference poses a significant challenge to this method, impacting resistance performance. This paper presents full-scale simulations using the CFD–DEM coupling method in brash ice channels, which is validated by comparing simulation results with ice tank measurements. By varying the distance between two ships from 0.05 to 5 ship lengths, ship–ship interference in full-scale brash ice channels is analyzed using the CFD–DEM coupling strategy. The study examines hydrodynamic and ship–ice interactions, ice resistance effects, and simulation results. It is found that ship-to-ship distance significantly influences the velocity field, dynamic pressure distribution on the hull, and hydrodynamic interaction forces. Distances less than one ship length result in increased water resistance for the forward ship and decreased resistance for the rear ship. The forward ship demonstrates favorable interference with the ice accumulation of the rear ship. When distances are less than two ship lengths, the ice resistance of the forward ship remains mostly unaffected, while the ice resistance of the rear ship decreases as the distance decreases. These insights enhance our understanding of ship–ship interference in formation navigation, aiding in the optimization of brash ice channel navigation strategies.

The repeated passage of ships through ice-infested waters create a field of broken ice pieces. The typical size of the broken ice pieces is generally <2.0 m. This area might be referred to as a brash ice field. The movement of ships and vessels leads to the transportation and accumulation of broken ice pieces in a brash ice field. A better understanding of the properties and behavior of brash ice could improve the estimates of ice load that are associated with shipping in a brash ice field. An in situ test referred to in this study as a pull up test will be performed in Luleå harbor, Luleå, Sweden. An attempt will be made to estimate the mechanical and physical properties of a brash ice field based on the in situ test results. The test setup, procedure, and test results will be described in detail. Furthermore, the test will be simulated using the smoothed particle hydrodynamics (SPH) formulation. The numerical simulations will calibrate the numerical and material model of brash ice using the pull up test measurements. In this numerical model, a discrete mass-spring-dashpot model will be used to simulate buoyancy and drag. The continuous surface cap model (CSCM) will be used as a material model for the brash ice. The elastic modulus and the fracture energy of brash ice as a material model input will be estimated by an ad hoc scaling formula. The parameters, such as void fraction (Vf), cohesion (c), and angle of internal friction (f) will be altered to assess their influence on the test data. The analysis of the in situ test results and the simulation results provide a preliminary approach to understand the brash ice failure process that could be further developed into modeling techniques for marine design and operations. [ABSTRACT FROM AUTHOR]

It is important to understand the properties and parameters of ice growth models, to enable reliable assessment of the impact ice may have on facilities or to ship navigation. To improve the understanding of the different models, the theoretical formulations for ice growth are investigated and calculated results compared with laboratory and full-scale measurement data. The paper describes the ice growth models for level sea ice and how these are applied in brash ice consolidation modelling. In particular, analysis is made to account for modelling of snow cover in level ice growth models, and subsequently also salinity, porosity and the atmospheric boundary including wind effect in brash ice models. The paper presents an overview of laboratory tests and results for both level ice and brash ice. Also models for level ice growth for the case of snow cover are derived and compared with thetest results. Specifically, inclusion of snow thickness in the growth model presents some practical difficulties, as the thickness of snow cover is often not known a priori, and comparison between calculated level ice thickness and measurements suggests that a good assumption in predictive models is to assume the snow cover thickness to be proportional to level ice thickness. Further, it was observed that the wind influences much the heat transfer to atmosphere, which is not zero at the zero wind speed, a value for the heat transfer coefficient to atmosphere is derived based on laboratory tests. The findings from these analyses provide an improved understanding of the ice growth and consolidation process which can be incorporated into modelling techniques for marine design and operations. • Models for brash ice growth and the parameters therein • Laboratory tests on brash ice growth, effect of porosity, salinity and wind • Values for atmospheric heat transfer coefficient with and without wind [ABSTRACT FROM AUTHOR]

• ·The effect of brash ice content on the pool fires were studied. • ·The brash ice melting behavior in pool fires burning was observed. • ·The heat transfer mechanism of pool fire with brash ice was analyzed. • ·Model of the mass loss rate and the melting rate were established. In-situ burning is an effective method for oil spill cleanup in ice-covered areas. Although brash ice is commonly contained in the oil spill, nearly no work has been conducted to explore the influence of brash ice on pool fire burning. Aiming at characterizing the influence of the brash ice content on pool fire, a series of small-scale pool fire experiments were conducted using burners with different sizes (5, 7.5, and 10 cm). The results show that the brash ice significantly affects the ignitability and burning behavior of pool fires. When the brash ice content exceeds the critical value, the pool fire with brash ice is non-ignitable. And during the brash ice melting process, the flame height and mass loss rate decrease with the brash ice content increasing. Based on the theoretical and heat transfer analysis, it was found that the heat transfer between the fuel and ice would decrease the mass loss rate. Furthermore, the dimensionless mass loss rate could be correlated with the dimensionless size of brash ice and brash ice content. In order to explore the brash ice melting behavior in pool fire burning, a dimensionless correlation was proposed to describe the melting rate. This work provides basic experimental data and understanding of burning behavior for pool fire with brash ice, which can inform more practical in-situ burning applications in ice-covered areas. [ABSTRACT FROM AUTHOR]

Abstract Brash ice growth in frequently navigated areas like fairways or ports is quick due to the 'freezing – breaking' cycle induced by sub-zero temperatures and ship traffic. This problem is very acute in ports in Arctic areas where the temperatures are very low for long durations and the ship traffic is frequent. In order to take adequate action in managing the brash ice, the forecasts of the amount of brash ice expected should be reliable. The aim of this work is to develop and validate these prediction methods. The growth model developed is based on extension of earlier growth models which modify the Stefan type growth modelling. The improvement on the earlier models is that the brash ice layer is divided into three layers (instead of two in earlier models): The consolidated layer just below the water level, the brash ice over the water level and the unfrozen brash ice below the consolidated layer. The thermodynamic model follows the Stefan formulation including only the heat flux from latent heat release upon freezing (Stefan, 1891 and e.g. Anderson, 1961). The modelling includes the cyclic breaking and refreezing. The validation of the model is made using measurements carried out in winter 2013 in Luleå port and in winter 2015 in Sabetta in the Yamal peninsula. Luleå data suggests that the sideways motion of brash ice due to ship motion and wake should be taken into account when assessing the brash ice thickness. The analytical calculation over-estimates the brash ice thickness in the actual channel but under-estimates the total amount of broken ice. When applied to Sabetta data, the analytical calculation predicts well the observed brash ice thickness. It can be concluded that the analytical method that does not take into account any radiation heat fluxes can be applied in the high Arctic where solar radiation plays a minor role and ice surface is clearly below zero. Highlights • A new thickness calculation routine for brash ice • Validation of the model with measurements in Lulea and Sabetta • Brash ice management is described [ABSTRACT FROM AUTHOR]

The paper presents results of research hydraulic processes at the intake structures of diversion power plants in winter. On the basis of the physical modeling results the flow characteristics of sluiceway channel of water intake on the river Issyk-Ata, Kyrgyzstan were determined. Statistical models of discharges of elements of sluiceway channel with their mutual influence were obtained, using the methods of experimental design and data analysis. The influence of the concentration of brash ice on the sluiceway channel and its elements is described. The comparison of experimental data with data obtained by other authors before is made by comparing flow coefficients. Recommendations for normal operation of ice pass at sluiceway track channel of water intake structure for diversion power plant are given.

For polar ship operating in the brash ice channel, self-propulsion performance prediction is a significant topic. In this paper, the CFD-DEM coupling method is presented to investigate self-propulsion performance of an ice-strengthened Panamax bulk carrier in brash ice channel. The hydrodynamic performance of propeller was simulated by CFD tool, while ice load was calculated by DEM method. The ship model was towed by a carriage with propulsion assistance of rotating propeller through brash ice in numerical simulation, which is consistent with ice tank test. In general, the simulation results could reproduce both ship-ice interaction and propeller-ice interaction processes in a reasonable way. Self-propulsion simulations in model scale under the loaded and ballast conditions were analyzed. As key parameters, the thrust, developed power, propulsion efficiency, as well as ice load on hull and propeller were calculated and compared with model test data. The results show that the difference between simulated power and the measurements in model tests is within 8.5%. The present work can provide a technical tool for hull line development of ice-strengthened polar ships and ship navigation guidance in brash ice channel. • We present a CFD and DEM coupling method to evaluate self-propulsion performance of polar merchant ship in brash ice channel. • We simulate the self-propulsion performance using towed propulsion method consistent with the ice tank test. • The simulation results are validated with experimental results, and the difference is within 8.5%. • The method could well reproduce ship-ice interaction and propeller-ice interaction. [ABSTRACT FROM AUTHOR]

In order to investigate the ice loads of an Arctic LNG carrier under different ice conditions, a series of model tests are carried out in an ice tank, the ship model is attached to the towing dynamometer and the resistance force is measured for the specified model speed in level ice, broken ice and brash ice. During the test observations, several phenomena, including the ice-hull interaction modes and the failure modes of ice are captured. Ice loads in level ice and brash ice condition present a characteristic of periodicity, while ice force fluctuated randomly in broken ice because of nonuniform distribution of ice foes. The results also show that ice resistance has a liner fitting relationship with the ship speed. The achievable speed in broken ice condition is almost 3.5 times of that in level ice with the same thickness. With the same thrust power and the same speed, in brash ice condition, the ship can transit the ice 2.7 times thickness of that in level ice condition. Besides, model test results are compared with the results derived from some empirical formulas and the empirical formulas appropriate for resistance estimation in different ice conditions are summarized according to the comparison result. Lindqvist formula is suitable for ice resistance in level ice condition, Zuve & Dobrodeev formula coincides well with the experimental result in broken ice condition, Dobrodeev formula is proper for ice resistance in brash ice condition. • A series of model tests of an arctic LNG carrier under different ice breaking conditions are carried out. • Several phenomena including the ice-ship interaction modes and the failure modes of ice are captured. • Ice loads in level ice and brash ice present a characteristic of periodicity, while ice force fluctuated randomly in broken ice. • The achievable speed in broken ice is almost 3.5 times of that in level ice. • Empirical formulas available for resistance estimation are summarized according to experimental measurements. [ABSTRACT FROM AUTHOR]

A large-scale shear apparatus has been originally developed and built to test the mechanical properties of coarse-grained material. It was used to evaluate the shear behaviour of brash ice. The brash ice blocks were collected at Luleå harbour in two separate measuring campaigns in March 2020 and March 2021. The shear cylinder was loaded with brash ice in Luleå port in two different locations for the two test campaigns, and the displacement-controlled shear tests were conducted. A vertical actuator was used to set a constant normal load and then a horizontal actuator was used to move the shear swing. In this setup, time, forces, and displacements were recorded at the forward and return stroke of the horizontal actuator. In total 6 shear cycles on two brash ice samples with axial stress of 4.8 kPa, 2 kPa and 1 kPa were performed. The test data was analysed to determine the relationship between shear stress and shear strain. The macro-porosity and confining axial force were found to be the most influential factors in determining the strength and deformation of the brash ice. Furthermore, an attempt has been made to estimate a few parameters of a material model known as the Continuous Surface Cap Model. • Brash ice properties. • Large-scale shear test. • Kinematic hardening. • Volumetric hardening. • Continuous Surface Cap Model (CSCM). [ABSTRACT FROM AUTHOR]

To investigate the impact of brash ice on the dynamics of the water exit of an axisymmetric vehicle, an experimental study was conducted on the water exit of an axisymmetric vehicle in brash ice using a water tank, launching system, control system, data acquisition system, and high-speed camera system. The brash ice zone was modeled using actual observational data from the Antarctic marginal ice zone off Wilkes Land in late winter. Brash ice was created from polypropylene material, and the influence of brash ice on the dynamics of the water-exit of the vehicle is analyzed. The results show that the collapse of bubbles during water-exit of a vehicle in the presence of brash ice creates a state of eruption, which splashes upward from the shoulder to the center of the vehicle, and the underwater cavities undergo shrinkage and shedding. The effects of brash ice on the magnitude of the force and moment on the vehicle during the process are diverse and operate in different directions. The overall deflection angle is greater than that under ice-free conditions. As water-exit speed increases, the splash time becomes earlier, and the extent of the splash becomes more dispersive. In addition, pressure falls as the vehicle approaches the water surface, and the extent and magnitude of pressure fluctuation during the whole water-exit process becomes more severe. [ABSTRACT FROM AUTHOR]