Ice Basin Research Articles

Features of Modeling the Load from Hummocks in the Ice Basin

Features of Modeling the Load from Hummocks in the Ice Basin

Results of Experimental and Theoretical Studies of the Possibilities of the Resonance Method of Ice Cover Destruction

Based on experiments carried out: in ice basins; with large-scale models of hovercraft in the field; with full-scale hovercraft, as well as using theoretical dependencies for calculating the stressstrain state of the ice cover from the action of moving loads, the possibilities (patterns) of the resonant method of ice destruction, i.e., by excitation of resonant flexural-gravity waves (FGW), were studied. Its physical essence, the expediency of its implementation by a hovercraft are explained, the possible areas of effective use of this method are indicated. The results of the information review on the topic of the work are given, on the basis of which the purpose of the research is set. When describing the viscoelastic nature of the relationship between stresses and strains in ice, the Kelvin-Voigt law of deformation of an elastically retarded medium was used. The theoretical bending potential energy density of an infinite plate was taken as a criterion for the ice breaking capacity of FGW. In this case, the condition is used that when it reaches a certain value, complete (with the opening of cracks) destruction of ice occurs. The initial data for these calculations are taken from the performed experiments. Dependences are given that make it possible to determine the parameters of a load moving at a resonant speed (hovercraft parameters) sufficient to destroy an ice cover of a given thickness under given ice conditions.

Особенности влияния формы кормовой оконечности современных крупнотоннажных судов на их ледовую ходкость при движении задним ходом

Object and purpose of research. Object of the study is the analysis of aft shape effect of modern heavy-tonnage ships on ice performance indices when moving astern. The purpose of the work is to identify additional specific factors that affect the performance of ice performance when moving stern first, which are usually not taken into account when considering moving ahead. Materials and methods. Material for the development are provided by the data from model experiments results, as well as previously published works devoted to the study of the ship's stern-first movement in ice. Main results. Models tests results of large capacity ice-going ships models moving stern first in an ice basin are analyzed. The phenomena of stern interaction with the ice cover in comparison with the mode of bow first movement are identified and discussed. Approximate estimates are done of the size of ice fragments formed when large capacity ships are moving astern. The obtained results create prerequisites for the development of a methodology for designing large capacity ships with increased ice-going capability. Conclusion. Analysis of heavy-tonnage vessel interaction with ice when sailing astern was carried out based on model tests in the ice basin. It was concluded that in order to develop the calculation procedure for ice resistance when the ship is sailing astern, it is necessary to elaborate new criteria for describing the main components of the ship hull lines and peculiarities of hull interaction with ice.

Ship operation in brash ice: results of investigations

The paper gives a review of the studies concerned with operation of vessels in brash ice. Recently, the ice conditions have received an ever increasing attention of the researchers related to the fact that shipping in the Arctic regions and freezing seas, as well as in inland waterways has been scaled up. One of the important fields of brash ice studies is specifics of sailing under these conditions and primarily determination of the ship ice resistance. The paper shows that theoretical methods combined with physical modeling in ice basins are used for determination of the ship ice resistance under brash ice conditions. The paper traces the evolution of theoretical models utilized for calculations. It is mentioned that the models are mainly based on loose material mechanics. A rapidly developing computer modeling of ship motion in brash ice based on discrete element method is considered. Physical modeling techniques used for modeling brash ice in ice basin are described, and challenges of experimental investigations are discussed. It is pointed out that experimental studies in ice basin can provide valuable data not only about ship ice resistance but also about the mechanisms giving rise to ice channels filled with brash ice. The paper describes the methods for studying operation of ship propellers in brash ice conditions. It is concluded that further research into brash ice is needed.

Modelling of a DP Drillship Advancing in Managed Ice Fields: Comparison Between Numerical Simulations and Ice Basin Tests

Modelling of a DP Drillship Advancing in Managed Ice Fields: Comparison Between Numerical Simulations and Ice Basin Tests

Modelling of Dynamically Positioned vessels and managed ice-field interactions using multiple regression techniques

Empirical models based on full-scale or model scale measurements are often preferred over high-fidelity numerical models when real-time predictions for ice actions on ships and floating offshore platforms are needed. This paper presents multiple regression-based empirical models for predicting a Dynamically Position (DP) controlled vessel and managed ice-field interactions developed using a large dataset from ice basin tests of two distinct DP-controlled vessels. The authors carried out a detailed analysis of measurements from two physical modelling programs for developing a unique database. A multiple regression modelling procedure was developed to predict the time-averaged and average peaks of forces and moment of the DP-controlled vessels due to ice actions in multiple configurations of managed ice-field. The models were validated using model scale measurements for the predictions of time-averaged and average peak responses. The models were then used to evaluate the effects of each ice-field parameter on vessel forces and moment and interaction event parameters. The models presented in this paper showed reasonable accuracy in predicting the effects of several ice-field parameters on the forces and moments of two distinct DP-controlled vessels in a range of realistic operating conditions.

The adhesive behavior of the polyethylene component in the “GP-ice” for studying the ice propulsion of the promising Arctic icebreakers

The maritime constituent is the crucial component of the Artic transport and logistics system. In the modern period of the development of science and technology, the ice model experiment in the experimental model basin is the main instrument of the research engineer, who creates and develops the existing arctic vessels forms. The article is dealt with the one of the aspects of the composite model ice (“GP-ice”) consisting of the polyethylene granules frozen into natural ice. The crucial factor providing the modelling conditions is the model ice strength reduction due to lower adhesion forces on the granules. The aim of this investigation was to assess the reliability of the existing data and to obtain the one’s own results in terms of the adhesion strength value at the normal fracture. The experimentation procedure in the NNSTU small ice tank is presented. The adhesive compound strength of the high-pressure polyethylene and ice at the normal fracture was determined. The analysis of results, which has satisfactory statistical characteristics, is presented. As the experiments results, the dependence of the adhesion strength value on the temperature inside the heat chamber (-20, -10) was revealed. The influence of the frozen surface boundaries was also significant and had a negatively impact on the results of the samples separation of a smaller dimension-type. In further the obtained results will be used in the mathematical models of the “GP-ice” deformation and fracture, as well as for improving the ice cover composite model for testing the promising Arctic icebreakers forms in the experimental model ice basin.

Estimation of Ice Thickness and the Features of Subglacial Media Detected by Ground Penetrating Radar at the Baishui River Glacier No. 1 in Mt. Yulong, China

Using ground-penetrating radar (GPR), we measured and estimated the ice thickness of the Baishui River Glacier No. 1 of Yulong Snow Mountain. According to the position of the reflected media from the GPR image, combined with the radar waveform amplitude and polarity change information, the ice thickness and the changing medium position at the bottom of this temperate glacier were identified. Water paths were found in the measured ice, including ice caves and crevasses. A debris-rich ice layer was found at the bottom of the glacier, which produces strong abrasion and ploughing action at the bedrock surface. This results in the formation of different detrital layers stagnated at the ice-bedrock interface and numerous crevasses on the bedrock surface. Based on the obtained ice thickness and differential GPS data, combined with Landsat images, the kriging interpolation method was used to obtain grid data. The average ice thickness was 52.48 m and between 4740 and 4890 m above sea level, with a maximum depth of 92.83 m. The bedrock topography map of this area was drawn using digital elevation model from the Shuttle Radar Topography Mission. The central part of the glacier was characterized by small ice basins with distributed ice steps and ice ridges at the upper and lower parts.

Lithological and geomorphological indicators of glacial genesis in the upper Quaternary strata, Nadym River basin, Western Siberia

Abstract. Analysing the genesis of Quaternary sediments is important for understanding the glaciation history and development of marine sediments in the northern part of Western Siberia. The problem is relevant since there is no consistent concept of the Quaternary sediment genesis in the north of Western Siberia. The formation of sediments is associated with marine, glacial and interglacial sedimentation conditions. The research objective is to identify the persistent features characterising the conditions of sedimentation and relief formation using the Nadym River basin as an example. The best method for studying this problem is a comprehensive analysis of the lithological, chronostratigraphic, petrographic and geomorphological studies of the Quaternary sediment upper strata. This study provides data from the analysis of the basic characteristics of quartz grains at the site. The rounding and morphology of the quartz grains provide evidence of possible glacial processing of some of the site strata. A petrographic study of selected boulder samples was performed. Some of them, by the shape and presence of striation, can be attributed to ice basins. The first use of a detailed digital elevation model applied to the study area made it possible to identify specific relief forms that could very likely be created during glaciations. Based on the analysis, we propose to consider the vast lake alluvial plains in the Nadym River basin as periglacial regions. This idea lays the lithological framework for understanding the reasons for the formation of the modern landscape structure. The materials and descriptions provided are of interest to researchers of Quaternary sediments, topography, vegetation and soil cover, particularly researchers engaged in revising the history of the natural environment development in the north of Western Siberia.

Estimation of pack ice concentration using histogram peak analysis and image subdivision

Numerous studies on icebreaking vessels have been reported recently owing to a potential increase in the number of passable Arctic routes. Model ship tests of pack ice models in ice basins have been actively conducted to investigate the performance of different icebreakers. The estimation of the pack ice concentration is critical as pack ice directly affects the performance of such experiment. In this paper, an algorithm that automatically determines the concentration of pack ice is proposed. This study aimed to measure the area of pack ice, based on digital images captured in an ice basin, using an image processing technique. A local binarization technique, coupled with image subdivision based on a quadtree structure, was developed. Independent thresholds were calculated for the subdivided images and rapid image separation was achieved. To demonstrate the accuracy of the proposed method, the concentration results obtained with the developed algorithm were compared with the manually measured data, with both results and data showing good agreement. The main advantage of the developed algorithm is that it facilitates the near-real-time estimation of the pack ice concentration from captured digital images.

Calculation Methods of Icebreaking Capability for a Double-Acting Polar Ship

As a key parameter, icebreaking capability is often used to judge whether a polar ship could navigate in level ice at a certain speed. This paper presents two methods to calculate icebreaking capability. The first one is a static method based on the estimation of ice resistance under different ice thicknesses and ship speeds. The second is a dynamic method that involves solving the equation of motion. A series of model tests with a double-acting icebreaking tanker were also carried out in the ice basin of the Krylov State Research Center to measure ice resistances. The simulated ice resistances were compared with model tests results for both ahead and astern running operations. The calculated icebreaking capability based on static and dynamic methods was validated with the model test result. A good agreement was achieved between measurement and simulation. The discrepancy between the model test result and the result simulated by the static or dynamic method was minor.

Efficient discrete element simulation of managed ice actions on moored floating platforms

The current design standard lacks the detailed approach to estimate managed ice actions, which in turn forces the industry to rely on ice basin model tests and calibrated numerical simulations. To address the need for a reliable assessment of managed ice actions on large-scale floaters, this paper proposes an efficient two-dimensional discrete element simulation with polygonal elements, which integrates smoothly with a mooring system modeling and a hydrodynamic force representation. The study aims at establishing a range of numerical parameters suitable for managed ice, as well as the boundaries within which the two-dimensional assumption remains acceptable. The study includes validations against the empirical data on isolated ice impacts and the towing model test conducted in the Hamburg Ship Model Basin (HSVA), for which the discrete element simulations demonstrate reasonable agreements. Using this validated tool, this paper conducts a case study using a hypothetical floater based on the Kulluk, a heavily studied conical drilling platform with years of deployment in the Arctic. The study examines the effect of different ice and mooring characteristics on the simulated load, which provides insights on the design of floating platforms and its mooring systems for managed ice conditions.

Application of continuum breakage mechanics to ice rubble modelling

The need exists for more accurate models to predict various ice loads including the load from ice rubble. When ice rubble is modelled as continuum, the derivation of a constitutive relationship requires tests with uniform strain fields. Here, the model is based on biaxial compression and oedometer (one-dimensional compression) tests available in the literature. Moreover, continuum breakage mechanics is used to introduce the ice-rubble parameters that are connected to the properties of constituting ice fragments. The developed model agrees with the ice-rubble load measured on a structure tested in an ice basin. For floating unconsolidated ice rubble, the model suggests that the load on the structure is governed by the ice-rubble accumulation rather that the breakage of ice fragments in it.

Water resistance forecasting of the icebreaking aircushion platform

The forecasting resistance method of the icebreaking platform, based on dummy tests in NSTU experimental model ice basin is proposed in the article. Experimental research data of ice breaking air cushion platforms resistance in calm water are presented. The dummy tests main results taking into account the key parameters influencing the platform resistance are given. The effect analysis of aircushion pressure, airflow, icebreaking platform velocity, aircushion size ratio in plan and the variable basin depth on wave resistance is made. The formula of water resistance calculation is proposed.

Method for estimation of icebreaker propulsion performance in ice

Classical methods of ship propulsion estimations based on the traditionally applied system of hull and propeller interaction coefficients are not suitable for prediction of icebreaker performance in ice. This is because the wake fraction tends to assume negative values in operating conditions typical of navigation in ice. This paper suggests an alternative system of hull/propeller interaction coefficients to overcome the problem. The alternative system comprises the thrust deduction factor t and the factors allowing for hull effect on thrust iTB and hull effect on torque iQB. An alternative method of ship propulsion performance estimations is developed based on this system of coefficients to take into account all characteristics of icebreaker sailing in ice. The method was used to analyze the full-scale data obtained from sea trials of the icebreakers Vladivostok and Novorosiisk. The initial data inputs for the analysis were ship speed in ice and consumed power measured during the sea trials. The number of propeller revolutions and ice resistance were calculated. The estimated propeller revolutions were compared with the full-scale data gathered during the sea trials in ice. The ice resistance was compared with the predictions based on model tests in ice basin. It is shown that at slow speeds in ice, ranging from 0.5 to 5.0 knots, the predicted number of propeller revolutions is in good agreement with the data measured during the sea trials. Propulsion performance of the Vladivostok icebreaker in 1.5-m thick ice was estimated

Purity and mechanical strength of naturally frozen ice in wastewater basins

A fairly clean ice cover can form over a contaminated water pond when the air-cooled surface of water freezes and impurities are efficiently expelled to the remaining water underneath. Natural freeze crystallization has recently been studied as a potential wastewater purification method with aqueous solutions on a laboratory scale. The effect of impurity inclusions on ice strength has been researched in model ice basins over the past few decades. It is of interest to discover how efficiently natural freeze separation works under real weather conditions before freezing can be utilized for wastewater treatment application. Herein, understanding the mechanical strength properties of naturally frozen wastewater (ice) is important when planning ice breaking and harvesting devices.This research implemented in-situ measurements of the flexural and compressive strength of ice in natural ice-covered environments of a freshwater lake, two peatlands and three mining site basins, and compares the determined strength with analyzed impurities of the ice. The results showed that despite varying ice growth conditions and initial water constituents, it was possible to deduce an evident yet simple relationship between mean ice strength and ice impurities: the more impure the ice is, the lower the value of strength is Based on this exploration, it was concluded that separation efficiencies, i.e. the impurity removal ratio between basin water and ice, from 65% up to 90% can be achieved by natural freezing.

A skewed movement of large-size ships in “narrow” ice channel

This work investigates a previously unknown phenomenon taking place when a large carrier ship moves in a channel made by an icebreaker narrower than the carrier ship. Usually, the studies of these movement conditions assumed the center line of the ship to coincide with the channel axis and the interaction of ship sides with channel edges to be symmetric. However, the observations made in Ice Basin and in real conditions have shown that in most of cases interaction of ship sides with channel edges is not symmetric. The ship moving in the channel breaks ice only with one of her sides, the other side only rubbing against the edge. The numerical assessments of ship position stability in the channel given in this paper made it possible to understand how this interaction becomes asymmetric. The study also yielded ice resistance assessments for a large carrier ship moving along the channel in these asymmetric conditions.

The action of long multi-year ridges on upward sloping conical structures

In ISO 19906 (2010), there are no algorithms provided for calculating loads on sloping structures due to interaction with multi-year (MY) ridges; only references are provided for a range of methods. A study was undertaken to review and improve the theories for MY ridge breaking and ride-up on a slope.This article reports on the new methods developed for long ridges which are defined as being long enough to develop both centre and hinge cracks. Short ridges, which are defined as being too short to develop hinge cracks, have also been investigated and new theories for short ridges are reported in an accompanying paper.The new method for long ridges includes a simplified approach for secondary failures of the hinge pieces which are successively broken as a ridge is pushed higher prior to rotation of the broken pieces around the structure. As well, for wide ridges, a new theory for failure across their width has been developed which leads to lower loads than if this failure mode is not included.Results using the new methods have been compared to tests conducted at the Imperial Oil outdoor ice basin in Calgary. These are the largest scale tests ever conducted in studying multi-year ridge loads on conical structures.A recommended methodology which includes closed-form equations for the various load components is presented. The method is considered suitable for inclusion in probabilistic methods and in future code developments. In this paper, examples of deterministic loads on typical Arctic structures are given.Continuing uncertainties are discussed and recommendations are made to address them.

쿼드트리 분할영상의 국부이진화를 통한 팩아이스 집적도 측정 알고리즘

Recently, many research works on the icebreaking vessels have been published as the possibility of passing Arctic routes has been increasing. The model ship test on the pack ice model in the ice basin is actively carried out as a way to investigate the performance of icebreaking vessels. In this test, the concentration of pack ice is important since it directly affects the performance. However, it is difficult to measure the concentration because not only the pack ice has uneven shape but also it keeps floating around in the basin. In this paper, an algorithm to identify the concentration of pack ice is introduced. From a digital image of pack ice obtained in the ice basin, the goal is to measure the area of pack ice using an image processing technique. Instead of the general global binarization that yields numerical errors in this problem, a local binarization technique, coupled with image subdivision based on the quadtree structure, is developed. The concentration results obtained by the developed algorithm are compared with the manually measured data to prove its accuracy.

Further study on level ice resistance and channel resistance for an icebreaking vessel

In this paper, further research is carried out to investigate the resistance encountered by an icebreaking vessel travelling through level ice and channel ice at low speed range. The present paper focuses on experimental and calculated ice resistances by some empirical formulas in both level ice and channel ice. In order to achieve the research, extra model tests have been done in an ice basin. Based on the measurements from model test, it is found that there exists a relationship between ice resistance, minimum ice load, maximum ice load and the standard deviation of ice load for head on operation in level ice. In addition, both level ice resistance and channel ice resistance are calculated and compared with model test results.