Browsing by Author "Suominen, Mikko"
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Item Analysis of structural safety of ice-going vessels in the Arctic and Antarctic(2016-06-13) Kurmiste, Andres; Suominen, Mikko; Insinööritieteiden korkeakoulu; Kujala, PenttiMaritime operations in the Arctic and Antarctic are driven by different causes. In the Arctic the gradual decrease of the ice cover opens up possibilities for new routes for shipping mainly the Northern Sea Route. In addition, Arctic operations are increasing due to the natural resources found in the region. The operations in Antarctic waters are mainly related to ocean research and supplying research bases with goods in the Antarctica. Both regions have severe ice conditions compared to other regions where ice may occur. This is due to these regions having multiyear ice in addition to first year ice. Therefore, to ensure the safety of the ships operating in those regions knowledge is require on loads occurring on the ship. There have been studies on the ice-induced loads based on full-scale measurements in Arctic and Antarctic waters. Though, no research has been made on how the different ice conditions affect the safety of the ships in those regions. The effects of ice conditions on the ice-induced loads have been studied before only in The Baltic Sea. However, only the effects of ice thickness on the loads were studied. Therefore, there are gaps in the knowledge on ice-induced loads and especially on the effects that ice conditions have on the ice-induced loads in polar waters. The thesis aims to analyze the effects of different ice conditions on the structural safety of ice-going vessels operating in polar waters. The ice conditions are categorized based on ice thickness and ice concentration. The structural safety is analyzed for local structures in ice strengthened areas of the hull. The results based on full-scale measurements onboard S.A. Agulhas II in the Antarctic were more reliable than the results measured onboard M/T Uikku in the Arctic. Since, S.A. Agulhas had 6 times more data on ice-induced loads, due to more time spent in ice. Nevertheless, the results were interesting, as generally for the bow both ships showed a decrease in safety indices with the increase of the ice thickness and ice concentration. However, for the stern an increase in safety indices was observed with increasing ice thickness and ice concentration.Item Antarctic sea ice properties on zero meridian side during Austral summers 2012-14 and 2018-19(2021-06-14) Suominen, Mikko; Lu, Liangliang; Kujala, Pentti; Bekker, Anriëtte; Department of Mechanical Engineering; Marine Technology; Stellenbosch UniversityPolar Supply and Research Vessel S.A. Agulhas II has visited Antarctic continent annually since her maiden voyage 2012. Commonly, the voyage duration is from December to Februaryor March. Aalto University and Stellenbosch University have been conducting ship and ice conditions related measurements with varying focus since the maiden voyage. The mechanical properties of sea ice (flexuraland compressive strength) have been measured during voyages 2012-13, 2013-14, and 2014-15 while the focus in voyage 2018-19 was in physical properties, i.e. the salinity, density, temperature, and grain sizeof ice.This paper presents themethods and results of these measurementsto contribute to therelatively rare dataset of Antarctic sea ice properties. The mean flexural strength was around 280 kPa. The measured compressive strength of sea ice varied from 100 kPa to 3.0 MPa in the vertical direction, and from 100 kPa to 1.5 MPain the horizontal direction, the averages being 740 kPa and 560 kPa, respectively. The shelf ice compressive strength varied generally from 100 kPa to 400 kPa with an average of 160 kPa.The measured ice temperature generally varies from air temperature on the top to -1.8°C in the bottom. Ice salinity varies from around 1‰ to 8‰ and ice density is in the range from 830to 940kg/m3.Item An Artificial Bee Colony optimization-based approach for sizing and composition of Arctic offshore drilling support fleets considering cost-efficiency(Schiffahrts Verlag Hansa, 2022-05-04) Kondratenko, Aleksandr; Bergström, Martin; Suominen, Mikko; Kujala, Pentti; Department of Mechanical Engineering; Marine TechnologyThis article presents an optimization-based approach for sizing and composition of an Arctic offshore drilling support fleet considering cost-efficiency. The approach studies the main types of duties related to Arctic offshore drillings: supply, towing, anchor handling, standby, oil spill response, firefighting, and ice management. The approach considers the combined effect of the expected costs of accidental events, the versatility of individual support vessels, and ice management. The approach applies an Artificial Bee Colony algorithm-based optimization procedure. As demonstrated through case studies, the approach may help to find a range of cost-efficient fleet compositions. Some of the obtained solutions are similar to corresponding real-life fleets, indicating that the approach works in principle. Sensitivity analyses indicate that the consideration of the expected costs from accidental events significantly impacts the obtained solution, and that investments to reduce these costs may improve the overall cost-efficiency of an Arctic offshore drilling support fleet.Item Beräkningsmetoder för fartygs motstånd i fast is(2011) Jaatinen, Juuso; Kujala, Pentti; Suominen, Mikko; Insinööritieteiden korkeakoulu; Marquis GaryItem Capacity of ice-strengthened structures subjected to different ice-loading scenarios(2017-02-20) Ghosh Dastidar, Sabyasachi; Korgesaar, Mihkel; Suominen, Mikko; Insinööritieteiden korkeakoulu; Romanoff, JaniThis thesis investigates the critical loading scenarios of multiple ice-strengthened ship structures when subjected to different load configurations. Evaluation of structural performance has been conducted using Non-linear Finite Element Analyses. Using a non-uniform pressure patch (NUPP), the capacity of ship structures was investigated and the safety margins against different capacity levels was determined. Results show that the point of yield and load for permanent deformation are highest for a structure built with IA Super ice class of the Finnish Swedish Ice Class Rules (FSICR). The values are observed to decrease for weaker ice classes. Although the present approach of FSICR is to design structures to yield once per winter, the safety factor against yield was about two for ice classes IA and IB, but slightly lower for IA Super. Comparison of different loading approaches, namely present design approach and non-uniform pressure patch, show that the FSICR approach yields much stiffer response. This justifies the use of less conservative NUPP for structural capacity evaluation, results of which show that the present FSICR design approach is extremely conservative. Alternatively, the current design pressure patch approach renders structures more safe than they actually are. Therefore, future investigations must clarify the pressure profile due to the ice loads.Item A CFD investigation of the effects of passing ship on a small size ice floe(Institute of Physics, 2023-08-09) Jiang, Zongyu; Suominen, Mikko; Tavakoli, Sasan; Kujala, Pentti; Hirdaris, Spyros; Department of Mechanical Engineering; Hirdaris, Spyros; Wan, Decheng; Marine and Arctic TechnologyA RANS (Reynolds Averaged Navier-Stokes) CFD STAR-CCM+ model is used to investigate the hydrodynamic interactions between a ship and a circular ice floe. The overset mesh technique is employed to simulate the advancing movement of the passing ship. The ship has a hull of similar configuration to the KCS MOERI container ship. The ice floe has a diameter of 30% of the ship's length and a thickness of 3 m. The paper primarily focuses on the motions of the ice floe and the hydrodynamic forces induced by the ship progressing in different speeds and calm water conditions. A parametric study on the influence of the ice floe surge and sway motions and associated hydrodynamic loads is presented. It is concluded that ship-generated waves can significantly affect the motions of the ice floe and the influence on sway is greater than that on surge. The ship speed is also found to have a distinct impact on ice floe motions.Item A CFD study on the hydrodynamic response of a small-scale ice floe induced by a passing ship(Elsevier Science Inc., 2024-04) Jiang, Zongyu; Hirdaris, Spyros; Tavakoli, Sasan; Suominen, Mikko; Kujala, Pentti; Department of Mechanical Engineering; Marine and Arctic TechnologyA Reynolds averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) model is built to investigate the hydrodynamic response of a circular ice floe under the influence of a passing ship in calm waters. The ship, mirroring the KRISO Container Ship’s hull design, progresses near an ice floe whose diameter is 30% of the ship’s length and its thickness is 3 m. The ship advances at a constant speed, which is handled by using the overset mesh technique. This study focuses on the ice floe’s motions and the hydrodynamic forces induced by three speeds and three transverse distances of the passing ship. Findings reveal that ship-generated wakes notably influence the ice floe’s motions, with a greater influence on sway than surge. Additionally, the ship’s speed and proximity distinctly affect the ice floe’s motions.Item A comprehensive approach to scenario-based risk management for Arctic waters(Schiffahrts Verlag Hansa, 2022-09-02) Bergström, Martin; Browne, Thomas; Ehlers, Sören; Helle, Inari; Herrnring, Hauke; Khan, Faisal; Kubiczek, Jan; Kujala, Pentti; Korgesaar, Mihkel; Leira, Bernt Johan; Parviainen, Tuuli; Polojarvi, Arttu; Suominen, Mikko; Taylor, Rocky; Tuhkuri, Jukka; Vanhatalo, Jarno; Veitch, Brian; Department of Mechanical Engineering; Marine Technology; Solid Mechanics; Memorial University of Newfoundland; University of Helsinki; Hamburg University of Technology; Norwegian University of Science and Technology; Tallinn University of TechnologyWhile society benefits from Arctic shipping, it is necessary to recognize that ship operations in Arctic waters pose significant risks to people, the environment, and property. To support the management of those risks, this article presents a comprehensive approach addressing both short-term operational risks, as well as risks related to long-term extreme ice loads. For the management of short-term operational risks, an extended version of the Polar Operational Limit Assessment Risk Indexing System (POLARIS) considering the magnitude of the consequences of potential adverse events is proposed. For the management of risks related to long-term extreme ice loads, guidelines are provided for using existing analytical, numerical, and semi-empirical methods. In addition, to support the design of ice class ship structures, the article proposes a novel approach that can be used in the conceptual design phase for the determination of preliminary scantlings for primary hull structural members.Item Corrigendum to “The influence of waves and hydrodynamic interaction on energy-based evaluation of ice loads during a glancing impact in sea states” [Ocean Engineering, (310), Part 1, 15 October 2024, 118719] (Ocean Engineering (2024) 310(P1), (S0029801824020572), (10.1016/j.oceaneng.2024.118719))(Elsevier Ltd, 2024-11-15) Jiang, Zongyu; Kujala, Pentti; Hirdaris, Spyros; Li, Fang; Mikkola, Tommi; Suominen, Mikko; Department of Mechanical Engineering; Marine and Arctic TechnologyIn the published version of this paper, there was an error in the formulation of Equations (14) and (15). The authors would like to correct these equations as follows: The original Equations (14) and (15) were incorrectly presented as: [Formula presented] [Formula presented] The corrected Equations (14) and (15) are now as follows: [Formula presented] [Formula presented] This correction does not affect the results or conclusions of the study because the computing code was compiled with the correct equations.Item Effect of Maneuvering on Ice-Induced Loading on Ship Hull: Dedicated Full-Scale Tests in the Baltic Sea(MDPI AG, 2020-10) Suominen, Mikko; Li, Fang; Lu, Liangliang; Kujala, Pentti; Bekker, Anriëtte; Lehtiranta, Jonni; Department of Mechanical Engineering; Marine Technology; Stellenbosch University; Finnish Meteorological InstituteManeuvers in level ice are common operations for icebreakers and polar supply vessels. Maneuvering exposes the midship and stern area to ice interaction, influencing the magnitude and frequency of ice-induced loading in these areas. However, full-scale measurements do not typically cover the midship and stern areas, as measurements have commonly focused on the bow area. Controlled maneuvering tests were conducted during the ice trials of S.A. Agulhas II in the Baltic Sea. During these tests, ice-induced loading at different hull areas was measured simultaneously with ship control, navigation, and ice condition data. This work studied the effect of maneuvers on the characteristics and statistics of ice-induced loading at different hull areas and compared the impact to ahead operations. The study showed that the maneuvers had minor impact to the magnitude, frequency, and duration of loading at the bow and bow shoulder. On the other hand, maneuvers had a clear effect on the load magnitude and frequency at the stern shoulder. Additionally, a statistical analysis showed that the load magnitude increased as a function of load duration in all hull areas. Furthermore, the analyzed measurement data are presented and made available with the paper.Item The effect of the extension of the instrumentation on the measured ice-induced load on a ship hull(2017) Suominen, Mikko; Kujala, Pentti; Romanoff, Jani; Remes, Heikki; Department of Mechanical Engineering; Marine TechnologyDue to the complexity of the ice-structure interaction, the knowledge about the ice-induced loads on a ship hull has been gained from full-scale measurements. As the instrumentation of the hull for the measurements is expensive, the extension is concerned at the planning phase. However, a narrow instrumentation can cause an error in the measurements, as the response of the adjacent frames with respect to the observed frame is not known. Thus, this paper studies the differences between loads measured from one or several frames on board S.A. Agulhas II. The difference results from the ability of the structure to transport loading internally. The results show that when the loads affect only an individual frame, the instrumentations give similar results. However, the difference increases with the load length and the loading that is determined can be 15% higher for one frame instrumentation for a structure similar to the aft shoulder of S.A. Agulhas II. Furthermore, the difference in the mean value and standard deviation of the measurement time histories can be up to 10%. The study presents a new efficient method to obtain a rough estimate of the possible difference in the measured results between extensive and narrow instrumentation.Item Enhancing System Capacity and Robustness by Optimizing Software Architecture in a Real-time Multiprocessor Environment(2004) Suominen, Mikko; Koskinen, Ilkka; Eloranta, Juha; Sähkö- ja tietoliikennetekniikan osasto; Teknillinen korkeakoulu; Helsinki University of Technology; Jormakka, JormaItem Equivalent ice thickness for evaluating ship resistance in ice(2015-04-27) Niiler, Hardi; Suominen, Mikko; Insinööritieteiden korkeakoulu; Kujala, PenttiThe current thesis investigates the Antarctic sea ice and found an equivalent value for evaluating ship actual resistance in ice. The full-scale measurements were conducted on board S.A Agulhas II in the Antarctic waters during 2013-2014. For ice resistance calculations the Lindqvist’s method was used. The equivalent ice thickness concept was taken as the geometric method, where all the ice forms in some certain area are taken into account and the result is given by one simple thickness value. The equivalent ice thickness of the ice was found using the real measurements data for level ice thickness, ridges height, snow thickness, ice concentration and the porosity of ridged ice. The work was based on the ten pre-selected cases, where each case was one hour period. Ice thicknesses were measured by stereo images, electromagnetic sounding and visually for all ten pre-selected cases. These three method’s results were compared by probability distributions and they show quite similar results, which confirms that the results are realistic. Ridges heights were measured from electromagnetic sounding figures. Snow thickness was measured in stereo images. The ice concentration was taken into account on the basis of visual observations. The calculated resistance of equivalent ice thickness has been compared with the ship average actual thrust, which was measured from the shaft line. After that, four suitable cases are selected for more detail analysis, where the periods were shortened to get smoother navigational parameters for ice resistance calculations. The results indicate that the ship actual thrust is similar with calculated ice resistance, although the final phase of the work the four different cases results have differed up to 33%. This result can be considered as good as the ice conditions were not as smooth as they might be and ice mechanical properties were not measured as tight as the thicknesses of the ice.Item Estimating operability of ships in ridged ice fields(2017-03) Kuuliala, Lauri; Kujala, Pentti; Suominen, Mikko; Montewka, Jakub; Department of Mechanical Engineering; Marine TechnologyA method for estimating ship's resistance caused by sea ice ridge keels is revised and used as a part of a method for predicting performance of ships in ridged ice conditions. The resistance method is based on a continuum plasticity model of ridge rubble and is simple to compute. The performance prediction method combines deterministic simulations of ship motion with probabilistic modelling of ridged ice fields. Performance estimates given by the model are distribution of attainable mean speeds for given ice conditions and probability of the ship being able to operate independently. A comprehensive sensitivity analysis was performed to gain insight into the model and identify possible problematic parameters. The sensitivity analysis covered both the ice conditions and modelling assumptions. Two data-sets were used to test the simulation method. One set included the depth profile of sea ice, machinery data and the speed of a ship operating in ridged ice. The resistance method was able to predict the mean speed over 3km well. The second data-set consisted of a history of ship's speeds and positions from AIS data and ice conditions estimated by a numerical ice model HELMI, developed in the Finnish Meteorological Institute. Observed mean speeds were mostly well within the distributions of mean speeds simulated by the transit simulation model. Predictions of independent operation were also promising.Item Estimation of propeller ice torque in preliminary design phase - Development of a numerical model(2024-06-10) Sevón, Miku; Lehtonen, Jesse; Suominen, Mikko; Insinööritieteiden korkeakoulu; Musharraf, MashruraPropeller-ice interaction crucially impacts ship's operational performance and safety in icy conditions. Ice torque, an essential design parameter for assessing a ship's propulsion system performance, refers to the additional rotational force applied to the propeller during interactions with ice. Estimating ice torque is challenging due to the randomness of ice loads. This thesis develops a method and a numerical model for the estimation of ice torque in preliminary design phase. The model, developed in MATLAB, utilizes a theoretical framework of propulsion system dynamics and full-scale propulsion data from existing reference ships to estimate ice torque for new designs. The model firstly calculates the reference ship ice torque inversely from propulsion motor torque and normalizes the result for a new design in preliminary design phase using scaling factors based on ice torque design regulations. Preliminary model assessment is conducted via comparative and sensitivity analyses. The model's maximum ice torque estimations matched the comparison data values with 84.3 to 93.3 % accuracy and qualitative similarities were found between the model estimates and the results of previous studies. Consistent performance was also proved with minimal sensitivity errors, ranging from -2.3 to 2.1 %, indicating low sensitivity. The numerical model was successful due to its comprehensive framework and usage of propulsion data. On the other hand, the accuracy of the model can be limited if the quality of the input propulsion data is insufficient. The main feature of the model is its ability to provide ice torque estimates, which can be used as key inputs for propulsion system simulations, enabling the optimization of the design. The model can be further developed through a broader validation process and by refining the normalization process.Item Evaluation of ice induced loads on ships in compressive ice(2014) Filipovic, Antonio; Suominen, Mikko; Sovelletun mekaniikan laitos; Insinööritieteiden korkeakoulu; School of Engineering; Kujala, PenttiItem Experimental study on friction coefficient correction method for model scale testing in brash ice channel(2022-01-24) Rehman, Aqeel; Suominen, Mikko; Insinööritieteiden korkeakoulu; Kujala, PenttiMaritime traffic in the polar regions has been surged in recent years due to a decrease in ice-covered areas. Climate change plays a pivotal role in contracting the ice thickness, which escalates the trade through the northern sea route. Navigation of icebreaker across uniform ice creates a broken channel in level ice. The recurrence of ships maneuvering through this broken channel causes the ice pieces to break and refrozen repeatedly, forming the brash ice channel. This channel is used by other ships as it offers less resistance than level ice. The resistance offered by brash ice channel is studied at model scale in this research. Model scale tests can be used to verify the performance of vessel before building a prototype. Model scale tests are economical and easily manageable compared to full-scale tests. In model scale testing, often, test parameters deviate from the target values. To recoup this situation, test results are corrected according to specific techniques. In the ice model test, deviation in friction coefficient between ship hull and ice is corrected using Finnish-Swedish Ice Class Rules (FSICR). This thesis aims to improve the friction coefficient correction method in brash ice channels using model scale tests. In this study, a simplified ship model is designed and manufactured. Paints of three different friction coefficients are used for brash ice tests. Brash ice channels are prepared according to the International Towing Tank Conference (ITTC) guidelines. Before brash ice channel tests, Ice-hull friction coefficients of each paint are measured. Two bow shapes (Round and Wedge) are tested in a brash ice channel. Total resistance, as well as its components, are measured during the test. Results from the tests are verified using ice resistance models developed in earlier research. These ice resistance models are developed using theoretical and experimental knowledge. Then, a new friction coefficient correction formula is proposed based on tests results.Item Experimental validation of an inverse method for the determination of ice loads on a ship hull(2022-05-16) Veltheim, Oskar; Suominen, Mikko; Ikonen, Teemu; Insinööritieteiden korkeakoulu; Kujala, PenttiThe decrease of the Arctic ice coverage enables increasing number of ships to operate in new shipping routes. To ensure safe operation in Arctic conditions safe and efficient ship designs are required. One important aspect of current ship-ice interaction studies is the determination of the extend of the ice load area, which is especially interesting in terms of structural design. The aim of this thesis is to develop and validate an inverse load determination method. The method is validated using experimental data, which was measured during the building phase of the ropax ferry Aurora Botnia. The data consists of measured strains and loads from sets of experimental loadings of the hull. This thesis presents an inverse method, which uses an influence coefficient matrix to represent the strain response of the structure to the unit pressure applied to discretization areas of a selected load discretization. The matrix is constructed based on the strain response of a finite element model, which is verified using the collected experimental data. The method determines the loading from the measured strains in the structure using the influence coefficient matrix and a simplified Tikhonov regularization equation. Based on the results, the inverse method succeeds to locate the load in a 3-by-3 grid load discretization in 42 of 46 loading events. The average relative error of determined load magnitude is 13.5 %. Three major sources for uncertainty are the inaccuracies of the experimental measurements, inaccurate finite element presentation of the real structure and the drift of the experimental strain data. These sources and possible solutions are discussed.Item A goal-based approach for selecting a ship's polar class(Elsevier Ltd., 2022-01) Bergström, Martin; Li, Fang; Suominen, Mikko; Kujala, Pentti; Department of Mechanical Engineering; Marine TechnologyFollowing the International Code for Ships Operating in Polar Waters (Polar Code), ships operating in ice-covered polar waters must comply with an appropriate Polar Class (PC) or equivalent ice class standard. For the selection of an appropriate Polar Class, ship designers and operators are encouraged to use the Polar Operational Limit Assessment Risk Indexing System (POLARIS). A limitation of POLARIS is that it does not consider the extent to which a ship operates in various ice conditions, and thus also not the probabilistic nature of ice loading. To address this limitation, this article outlines a goal-based approach that is intended to complement POLARIS when selecting a ship's Polar Class. Following the proposed approach, the appropriateness of a ship's minimum required Polar Class as determined using POLARIS is evaluated by assessing the ship's long-term extreme ice loads, and by relating these to the design loads behind the considered Polar Class standard. To account for the probabilistic nature of ice loading, the approach calculates a ship's long-term extreme ice loads considering its intended operating profile and expected ice exposure. This is achieved by synthesising a modified version of the so-called event-maximum method, discrete-event simulations, and satellite ice data. The utility of the proposed approach is demonstrated through a case study, in which it is used as a complement to POLARIS to select an appropriate Polar Class for a double-acting ship intended for year-round independent operations along the northeast coast of Canada.Item Impact of ship speed on ice-induced loads on ship hull(2024-08-19) Kemppinen, Inkeri; Valtonen, Ville; Insinööritieteiden korkeakoulu; Suominen, MikkoThe reduction of ice cover in the Arctic due to climate change has sparked interest in Arctic shipping as potential new shipping routes open up. However, while the ice cover may decrease, the ice conditions may become more unpredictable. Therefore, it is crucial to understand how different operational parameters affect the ice-induced loads on a ship hull. One of these operational parameters is the speed of the ship. While multiple studies have been conducted on its impact on ice-induced loads, no clear consensus has been reached. Hence, further study on the topic is required. The aim of this thesis was to study the effect of ship speed on the local ice-induced loads on a ship hull. Data collected onboard icebreaking polar supply and research vessel S. A. Agulhas II was utilized in the study. The data included ice load measurements, visual observations of ice thickness, and the speed of the ship collected with GPS. The ice load measurements were divided into smaller datasets, first based on ice thickness and then on speed. These datasets were studied with quantiles and a three-parameter Weibull distribution. The study concluded that the magnitudes of the highest ice-induced loads decrease with increasing speed in ice thicknesses less than 160 cm. In ice thicknesses over 160 cm, the loads seemed to stay approximately constant regardless of speed. Possible explanations were identified in the severity of ice conditions, the ship's bow waves, and the load patch's development during ship-ice interactions.
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