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Keywords: model experiment
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Proceedings Papers
Paper presented at the The 29th International Ocean and Polar Engineering Conference, June 16–21, 2019
Paper Number: ISOPE-I-19-536
... rate of 0.1 mm/s. The data was measured every 0.01 sec. The depth of cover H was 140 mm (i.e. H/D=2.0) Experimental Cases In addition to the previous works (Ohta, 2018), four model experimental cases were performed in this study as shown in Table 3.Ohta et al. (2018) conducted the model experiments...
Abstract
ABSTRACT Serious damage of buried pipelines is caused at the bends due to thrust force. In the current design in Japan, the sliding factor for pipelines against thrust force is determined by the passive earth pressure without considering bending angle and under two-dimensional conditions, whereas the soil failure is expected to be caused three-dimensionally. In this study, in order to clarify the uncertainty, lateral loading experiments have been conducted for model pipes. The results of the experiments show the bending angle slightly relates to the lateral resistance force and the soil failure was caused under three-dimensional conditions. INTRODUCTION Buried pipelines such as agricultural pipelines are damaged due to earthquake. In particular, in the pipe bend, serious damage such as uplifts and separations of pipe joints is caused due to unbalanced force called thrust force, which is always applied due to centrifugal force by water flow and disproportion of water pressure. Thrust force depends on the bending angle and the internal water pressure as expressed in Eq.(1). (Equation) Where, P ' = thrust force (kN), p = design water pressure (kN/m 2 ), a c = cross-sectional area of pipes (m 2 ), θ = bending angle of pipes (°). In Japanese current design standard, the passive earth pressure behind pipes is given as resistance force against thrust force and the sliding safety factor is determined by the magnitude of the passive earth pressure (MAFF, 2009) as shown in Fig. 1. The resistance force is calculated based on the Rankine's theory as expressed in Eq.(2). (Equation) Where R h = the lateral resistance by passive earth pressure (kN), F = the correction factor for the passive earth pressure acting on the curve ( F is 0.65 in the Japanese current design standard), K p = the coefficient of passive earth pressure [tan 2 (45°+ ϕ /2)], ϕ = the inner friction angle (°), γ = the unit weight (kN/m 3 ), H 1 = the depth from the ground surface to the top of the pipes, H 2 = the depth from the ground surface to the bottom of the pipe, B b = the projected width behind the pipe as shown in Fig. 2. Here, the calculation formula for R h is open to some discussion. a.) The formula depends on the projected width ( B b ). In other words, the effects of the bending angle - are not considered at all. b.) Rh expresses the resistance force under the two-dimensional failure strain conditions and ignores the side friction of soil wedge, whereas the soil wedge is expected to cause the three-dimensional failure because B b is the finite width. The effects of the failure are likely to depend on the interface friction between the pipe surface and backfill. c.) If the soil slips along the pipe surface as shown in Fig. 2, the width receiving the resistance force may be smaller than B b .
Proceedings Papers
Paper presented at the The 29th International Ocean and Polar Engineering Conference, June 16–21, 2019
Paper Number: ISOPE-I-19-538
... lower end interaction mechanical behavior sheet-pile extraction model experiment right pipe deflection ground density deformation experiment flexible pipe left pipe pipe sheet pile extraction extraction twin pipe pipeline pile extraction model pipe Model Experiments on...
Abstract
ABSTRACT Twin pipelines are often constructed in one trench for effectiveness of water management. However, in the Japanese current design for pipelines, interaction of twin buried pipes is not considered at all and they are treated same as single pipes. In this study, in order to clarify the influence of the sheet pile extraction on twin buried pipes, model experiments were conducted. As a result, it has been revealed that the deflection of the twin buried pipes is less than that of a single pipe and the reduction of the deflection depends on the distances between the twin pipes. INTRODUCTION Twin pipelines are often constructed in one trench for the efficient distribution of agricultural water as shown in Fig. 1. In the current Japanese design guidelines for irrigation pipelines (MAFF, 2009), the distance between twin pipes has been described. However, this distance was decided only due to the workability and economy for the construction of pipes regardless of the soil-pipe interaction. In other words, the influences of the distance on the mechanical behavior of pipes have not been considered yet. Additionally, sheet piles have often been used in Japan to install pipelines under poor ground conditions such as the soft ground and high ground-water levels or because of limited work sites. The installed sheet piles are generally extracted after the completion of backfilling. During sheet pile extraction, large deformation and change of stress condition are caused in the surrounding soil. Hence, it has been reported that excessive deformation and cracks occur in flexible and rigid pipes respectively. In many past researches, the influence of the sheet pile extraction on single pipes has been studied. For instance, Mohri et al. (1987) conducted field tests for single buried FRPM (Fiberglass Reinforced Plastic Mortar) pipelines with a large-diameter to examine the changes of the deformations of pipes and the earth pressure distribution due to the sheet pile extraction. Yoshimura et al. (1997) conducted centrifuge tests for single buried flexible pipes to investigate the mechanical behavior of the pipes with the extraction. As the study on twin buried pipes, Kawabata et al. (1991; 1992) conducted a series of loading tests and FEM analyses for twin buried flexible pipes, and investigated the mechanical behavior of the pipes. Mohri et al. (1999) conducted field tests for twin buried pipes with large-diameter, and evaluate the safety of the twin pipes. Moreover, Young et al. (1984) proposed the calculation methods for the vertical pressure applied to the twin or more rigid pipes in single ditch, but these methods didn't include the case of the flexible pipe and the coefficient of subgrade reaction.
Proceedings Papers
Paper presented at the The 29th International Ocean and Polar Engineering Conference, June 16–21, 2019
Paper Number: ISOPE-I-19-256
... characteristics of ships, especially high-speed ships, in shallow water differ significantly from those in deep water. In this paper, model experiments of a patrol craft were conducted to determine the effect of shallow water on its resistance and sinkage. Firstly, the bare- hull and the hull with part of...
Abstract
ABSTRACT The resistance characteristics of ships, especially high-speed ships, in shallow water differ significantly from those in deep water. In this paper, model experiments of a patrol craft were conducted to determine the effect of shallow water on its resistance and sinkage. Firstly, the bare-hull and the hull with part of appendages (rudders, propeller shafts and deadwood) were used to conduct the resistance experiments in shallow water. Secondly, the influence of the angle of the stern wave suppression plate on the reduction of resistance in shallow water was discussed. Additionally, the wave eliminating appendages were adjusted to two different geometric shapes to investigate the differences of resistance resulting from the shape. The model tests were also carried out in deep water for comparison. Finally, the best appendages of the patrol craft in shallow water were presented based on the experimental results. INTRODUCTION The inland navigation plays an important role around the world. The influence of shallow water on the ship resistance is one of the most challenging problem for inland ships. Unlike in deep water, flow separation usually occurs in shallow water. And it is well known that the accuracy of turbulence model employed in RANSE approach is problematic when flow separates. In consequence the accuracy of CFD computation in predicting resistance in shallow water is unreliable. Zhihong et al. (2002) analyzed pressure variation caused by moving ship in shallow water and developed a conversion formula. Zou and Larsson (2013) developed a numerical study of the ship-to-ship interaction in shallow water using a steady Reynolds Averaged Navier-Stokes solver. Lilan and Gao (2013) proposed a method that coupled a potential flow theory with a wave spectrum method for calculating the wash waves of high speed displacement ships. Deng et al. (2014) predicted the resistance and sinkage of two different ships in shallow water through CFD computation and assessed its accuracy. Shuai et al. (2015) investigated the characteristics of ship resistance and flow field in shallow water. Rotteveel and Hekkenberg (2015) presented the effects of the hull form variation and shallow water on a 110-meter inland ship. Mucha et al. (2016) compared and validated two methods used in numerical prediction of ship sinkage and resistance in shallow water. Pacuraru and Domnisoru (2017) developed numerical analyses for the viscous flow around a barge hull and investigated the shallow water effect on the barge ship resistance. Mucha et al. (2017) conducted resistance and propulsion model tests of a modern inland waterway ship to provide reference data for benchmarking of numerical methods.
Proceedings Papers
Paper presented at the The 29th International Ocean and Polar Engineering Conference, June 16–21, 2019
Paper Number: ISOPE-I-19-283
..., rather than rely on planar two-dimensional mod els(Nagayama,2016;Nagayama,2017). case 1 velocity head model experiment modeling coastal urban flooding scenario cross section breakwater upstream oil & gas case 2 flow velocity water level specific energy experiment case 0 mesh...
Abstract
ABSTRACT The 2011 Great East Japan Tsunami caused enormous damage to coastal urban areas in the Tohoku region of northeast Japan, despite numerous engineered breakwaters. Conventional two-dimensional shallow-water models of urban inundation, and tsunami wave-pressure models that approximate hydrostatic pressures on a single building, do not accurately predict actual flooding processes or tsunami wave-pressures. This study investigates urban flooding scenarios in which the tsunami overtop breakwaters, explicitly evaluating tsunami waveforms, typical breakwater shapes, and typical building placements based on model and numerical experiments. We propose use of specific energy rather than hydrostatic-pressure approximations to model wave pressures on multiple buildings. INTRODUCTION The Japanese government has classified the tsunami initiated by the 201 1 Great East Japan Earthquake as a Level 2- and Level 1 tsunami (L2 ts unami and L1 tsunami, respectively) and has recommended implementa tion of additional disaster-prevention activities in response to each type of tsunami. The basis of this disaster-prevention activity is a tsunami ha zard map, which depicts the supposed inundation caused by a tsunami b ased on predictions. Such a map has been created and released in almost all coastal municipalities in Japan (Shuto et al.,2007;Arikawa et al.,2013). However, these inundation simulations are based on a two-dimensio nal shallow-water model in which the effects of coastal structures such as breakwaters cannot be evaluated. Previous studies have pointed out t hat the actual range and level of inundation during the 2011 Great East Japan Earthquake was vastly different from the expectations recorded o n previous tsunami hazard maps and have suggested that these differenc es are caused by factors such as the breakwater shape (Yanagawa et al., 2016). Simply put, to improve the accuracy of conventional tsunami haz ard maps, it is necessary to use a three-dimensional numerical model ca pable of taking into account the three-dimensional arrangement and sha pe of coastal structures, rather than rely on planar two-dimensional mod els(Nagayama,2016;Nagayama,2017).
Proceedings Papers
Paper presented at the The 29th International Ocean and Polar Engineering Conference, June 16–21, 2019
Paper Number: ISOPE-I-19-056
... the ship's tops. The visor gate dimension is as follows; Span : 57m, Crown height : O.P.+7.4m, Height of gate : 11.9m. Here O.P. stands for Osaka Peril. model experiment dissipater hydroplane tsunami barrier wave height removable breakwater breakwater tsunami energy visor gate variation...
Abstract
ABSTRACT A river gate may become an effective tool to prevent the tsunami-run up in the river. The gate which is originally designated for storm surge mitigation, is capable to prevent the tsunami-penetration into the river becomes necessary to reduce the tsunami pressures. The paper describes the applicability test on the removable river gate and its reduction rate for the wave parameters. INTRODUCTION Tsunami hazards cause the wide inundation in the innermost area with law ground heights as well as port and coastal areas. Such the inundation hazards become remarkable in case that the tsunami runs up along a river. A river gate may become an effective tool to prevent the tsunami-run up in the river. The gate, which is originally designed for storm surge mitigation, is capable to stop the tsunami-penetration into the river mouth. In case that its strengthen is not endurable against the tsunami impulsive pressures, a tsunami energy dissipater becomes necessary to reduce the tsunami pressures acting the river gate. The tsunami energy dissipater may lie on the sea bed in normal dates and it has to stand up in the emergency time like tsunami coming. So it should be removable and be enough strong against the external forces. The Hydro-Plane type movable tsunami breakwater has been developed since 2014 to prevent the tsunami energy at the mouth of a harbor (Azuma et al., 2014, 2015, 2016). Figure 1 shows the image of the Hydro-Plane type removable breakwater. The breakwater consists of a base plate, a flouter and tension-tied rubbers. The flat float connected in rubber belts is capable to stand in the positive wave coming and also it stands up in negative waves. Standing by the negative waves becomes the prevention of dispersion of debris due to tsunami. The target river in the research is Aji-river flowing at the central area of metropolitan Osaka, west Japan. The river gate was constructed in 1970 and the type is Visor-gate. Photo 1 shows the overview of the gate. Just after the construction, river transportation by ship was the peak so the top of the gate becomes higher than the ship's tops. The visor gate dimension is as follows; Span : 57m, Crown height : O.P.+7.4m, Height of gate : 11.9m. Here O.P. stands for Osaka Peril.
Proceedings Papers
Paper presented at the The 28th International Ocean and Polar Engineering Conference, June 10–15, 2018
Paper Number: ISOPE-I-18-394
... model experiments. INTRODUCTION So far, many Japanese coastal researchers have made effort on the tsunami fluid analysis, and the Japanese government has implemented tsunami disaster prevention measures. But the unexpected huge tsunami devastated Tohoku area in The 2011 Great East Japan Tsunami. With...
Abstract
ABSTRACT The 2011 Tohoku-oki Tsunami demolished a number of breakwaters in various forms, so we should investigate the failure mechanisms of breakwaters and their external forces; tsunami flows around breakwaters. When a tsunami strikes a caisson-type breakwater, the tip of the tsunami runs vertically up the front face of the structure. Herein, this phenomenon is called the tsunami jet flow. However, the relationship between the behavior of tsunami jet flow and the front slope of the breakwater has not fully understood yet. This paper discusses the above relationship by physical and numerical model experiments. INTRODUCTION So far, many Japanese coastal researchers have made effort on the tsunami fluid analysis, and the Japanese government has implemented tsunami disaster prevention measures. But the unexpected huge tsunami devastated Tohoku area in The 2011 Great East Japan Tsunami. With this background the Japanese government proposed the idea o "persistent structures"; even when an unexpected huge tsunami would attack, breakwaters are able to keep effect of the facilities. After the proposal, a number of studies were carried out on the destruction phenomena of structures caused by the tsunami. For example, Arikawa et al(2013) showed that when a tsunami overflows a breakwater, the breakwater safety margin can be evaluated by investigating hole sections which the tsunami dig behind the breakwater. It has been said when a huge tsunami attack a coastal the structure tsunami pressure can be represented by an impact wave pressure and a sustained wave pressure(Shuto et al,2007). An impact wave pressure is caused by rapid pressure rise in a short time, whereas a sustained wave pressure can be measured by gauge pressure. Especially, such an impact wave pressure usually generates three-dimensional flows around a structure. However, the phenomenon is difficult to reproduce in conventional two-dimensional numerical model which simplifies the flows by integrating in the depth direction to decrease a numerical cost. Moreover, conventional cartesian grid is difficult to reproduce a shape of complicated structures.
Proceedings Papers
Paper presented at the The 28th International Ocean and Polar Engineering Conference, June 10–15, 2018
Paper Number: ISOPE-I-18-550
... necessary to perform an outlier analysis when analyzing the model experimental data. The existing statistical analysis method is likely to lead to misinterpretation results due to the outliers due to lack of convergence of model experiments. The function approximation method using the most commonly used...
Abstract
ABSTRACT The present paper introduces outlier analysis of sloshing-induced random impact pressure. Analysis of outliers is one of the essential steps in the study of conducting experiments and data analyses. However, it is difficult to find systematic study of outlier analysis in sloshing load problem due to the statistical characteristics of probabilistic distribution of sloshing impact pressure. In this paper, outlier analysis, which is a method to improve convergence through statistical analysis on experimental sloshing pressures lacking convergence, was developed. In order to validate the outlier analysis method, a series of 1:50 scale sloshing model test was carried out for 138k LNG cargo hold. From this study, it can be found that existing statistical analysis method is likely to lead to misinterpretation results due to the outliers due to lack of convergence of model experiments. Also, when the outlier analysis is performed, it is possible to reduce the distortion of the analysis result caused by the outliers and to predict the sloshing load more reliably based on the same model test data. INTRODUCTION Sloshing is one of the key issues in the design of cargo holds for Liquefied Natural Gas (LNG) Carriers and other LNG-related offshore structures such as LNG-FPSO and FSRU. The interpretation of the sloshing phenomena within an LNG cargo is generally the use of experimental methods rather than analytic or numerical methods due to the complexities of physical phenomena. Earlier, Mathiesen (1976) and Gran (1981) made pioneering achievements in statistical analysis of the sloshing problem. Mathiesen (1976) conducted a model test of irregular swaying motion and applied statistical analysis to the Weibull distribution function. Gran (1981) performed statistical analysis by applying the model test results to the Frechet distribution function. Graczyk et al. (2006, 2008) presented a systematic method of analyzing sloshing problems covering ship motion analysis, model test, structural response, and statistical analysis. Based on previous studies, many international classifications have published their guides or procedures for estimating sloshing design loads. The procedure of the International Classification Society is similar in that it estimates the sloshing load through the model test. However, each Classification is building its own procedure in the method of performing model test, analyzing experimental data, and estimating sloshing design load. The International Classification Society states that long-term model tests should be carried out to obtain sufficiently converged results for sloshing load prediction, but there is no clear standard (LR 2009). It is known that the minimum recommended time of the proposed model experiment is significantly lower than the convergence time (Kuo et al., 2009; Fillon et al., 2011; Kim et al., 2014).
Proceedings Papers
Paper presented at the The 28th International Ocean and Polar Engineering Conference, June 10–15, 2018
Paper Number: ISOPE-I-18-557
... navigation channels and applicability for general ship shape in a harbor. Through several sets of numerical simulations representing ship waves measured in model experiments, a tuning parameter related to the ratio of ship width and length to computational mesh size is introduced for each approximation...
Abstract
ABSTRACT In recent busy ports and harbors, their tranquility must be affected with not only storm waves propagated from outside but also harbor waves generated by inside ship navigation. In this study, a new generation method of ship waves is developed and installed to a Boussinesq-type wave transformation model, considering expandability of setting of ship navigation channels and applicability for general ship shape in a harbor. Through several sets of numerical simulations representing ship waves measured in model experiments, a tuning parameter related to the ratio of ship width and length to computational mesh size is introduced for each approximation function of ship shape. INTRODUCTION On harbor tranquility analysis, a distribution of wave height inside a harbor is usually estimated with a numerical wave transformation model, considering wave diffraction around breakwaters and wave reflection on seawalls. Recently, many kinds of nonlinear wave transformation model, e.g. Boussinesq-type, have been employed to simulate wave field in shallow water. NOWT-PARI (NOnlinear Wave Transformation model by Port and Airport Research Institute) produced by Hirayama (2002), which has been already widely used to estimate harbor tranquility in Japan, is one of them. By dealing with several boundary conditions, it can reproduce the wave transformation in a harbor and a coastal area in random seas (Hirayama, 2013). In recent busy ports and harbors, their tranquility must be affected with not only storm waves propagated from outside but also harbor waves generated by inside ship navigation. The ship waves are, however, not always focused on in coastal engineering except by a few researchers because their height and period are usually smaller than storm wave's height and period. On the other hand, though the ship waves are studied in naval architecture in order to reduce one of sailing resistances (e.g. He et al., 2017), their propagation and transformation are rarely focused on.
Proceedings Papers
Paper presented at the The 28th International Ocean and Polar Engineering Conference, June 10–15, 2018
Paper Number: ISOPE-I-18-684
... pressure distribution straight pipe earth pressure lateral resistive force engineering lateral resistance pipe displacement lateral displacement resistance model experiment pipe bend Model Experiments on Influence of the Bending Angles on Lateral Resistance Acting on Buried Pipe Bends Yoko...
Abstract
ABSTRACT Damage to buried pipeline has often occurred at the bend section during earthquakes due to a thrust force. Although the passive earth pressure behind the pipe is expected as the resistive force that act against the thrust force in the current design, there have been few studies that focused on the influence of the bending angles on the mechanical behavior of the pipes. In this study, the lateral loading experiments have been conducted for model pipes buried in sandy soil with various bending angles. The result of the experiments showed that the bending angle of the pipe has no influence on the force-displacement relationship under the present experimental condition. INTRODUCTION In a bending section of pressure pipelines such as agricultural pipelines, un-equilibrium force called thrust force always acts depending on the internal pressure and bending angle. According to the current Japanese design guidelines for irrigation pipelines (MAFF, 2009), the passive earth pressure behind the pipe is expected as the resistive force that acts against the thrust force. In other words, the stability of the pipe bend has been evaluated by comparing the thrust force and the passive earth pressure acting on the bend. When the stability of the pipe bend cannot be maintained, a thrust block made of concrete is placed on the bending section to prevent the pipe bend from detaching. However, in the current design, the magnitude of the passive earth pressure is calculated simply in two dimensions, and the bending angle is not reflected in the calculation of the resistive force. Past experimental studies on the lateral behavior of buried pipes subjected to the external force can be divided into two groups, those using a straight pipe and those using a pipe bend. As the experiments using straight pipes, Trautmann and O'Rourke (1985) and Audibert and Nyman (1977) conducted the lateral loading experiments and proposed the relationship between the lateral displacement and the lateral resistance. Ono et al. (2017a) also carried out the lateral loading tests in liquefied soil and proposed the force-displacement relationship which takes into consideration the effective stress of the soil. As the experiments using pipe bends, Mohri (1996) conducted a full scale experiment on the pipe with bending angle of 90° under internal pressure. Kawabata et al. (2009) performed a lateral loading experiments on the real scale pipe with the bending angle of 45°. Itani et al. (2016) carried out a shaking table test on a flexibly jointed pipe with the bending angle of 45°.
Proceedings Papers
Paper presented at the The 28th International Ocean and Polar Engineering Conference, June 10–15, 2018
Paper Number: ISOPE-I-18-670
...; Zhang et al., 2017). However, there is little research on motion control of a disk-type underwater glider. controller passenger transportation nakamura vertical tail wing subsea system vehicle luna air transportation disturbance model experiment underwater glider weight shifter disk...
Abstract
ABSTRACT Recent years have highlighted that the necessity of ocean data in time and space for the predictions of environmental changes on Earth. As one method of acquiring data, we propose a virtual mooring system using an underwater vehicle. We have developed a disk-type underwater glider. Using the glider, oceanographic observations were conducted in the East China Sea in July, 2016. The details were presented at ISOPE2017. As described in this paper, results of model tests related to course control conducted to improve the performance of virtual mooring are presented. Then the influence of a vertical tail wing on motion control is discussed. INTRODUCTION In recent years, predictions of environmental changes on Earth and studies of ecodevelopment have become increasingly important. Such predictions necessitate the continuous collection of ocean data in time and space. However, construction of a conventional mooring system is laborious and expensive. Profiling floats such as Argo floats (Roemmich et al., 2009), because they float in the current, cannot remain at a specific point where continuous and long-term observations are needed. To resolve these difficulties and to collect the necessary data, we propose a virtual mooring system using an underwater glider. Construction of a prototype vehicle was begun at the Research Institute for Applied Mechanics (RIAM), Kyushu University in April 2010 (Koterayama et al., 2012). Some practical underwater gliders are already in use throughout the world (Eriksen et al., 2001; Sherman et al., 2001; Webb et al., 2001). However, they are cruising-type gliders, with a shape resembling that of a conventional airplane. The disk type underwater glider that we are developing has an appropriate form for virtual mooring and loading of an Acoustic Doppler Current Profiler (ADCP). Using this disk-type underwater glider, the BOOMERANG , oceanographic observations were made in the west sea-area of Japan's Kami-Goto islands in July, 2015 and in the East China Sea in July, 2016 yielding interesting data (Nakamura et al., 2017). Since those observations, research to improve the virtual mooring performance has continued. For this purpose, it is thought that a feedback control of the vehicle heading angle is desirable. Many researches on motion control of a vehicle have been carried out (Tran et al., 2014; Roy et al., 2015; Li et al., 2015; Wang et al., 2016; Zhang et al., 2017). However, there is little research on motion control of a disk-type underwater glider.
Proceedings Papers
Paper presented at the The 28th International Ocean and Polar Engineering Conference, June 10–15, 2018
Paper Number: ISOPE-I-18-212
.... And the shaft power of full-scale ship is predicted based on CFD simulations and model experiments. The rest of this paper is organized as follows: Section 2 presents the self-propulsion experiments schemes and briefly reviews the relevant CFD simulations and resistance model experimental results. The...
Abstract
ABSTRACT In recent years, air film lubrication has been attractive as a technology of reducing energy consumption and emissions from ships. This paper firstly investigates the influence of air flow rate and air injection position on propulsion performance of a 20000DWT bulk carrier mainly using model experiments. The self-propulsion experiments were conducted in seven different air injection conditions. During the experiments, the air film was formed at the bottom of ship and spilled from the two sides before flowing into the propellers. The thrust, torque and self-propulsion factors of ship with air film and without air film are compared and discussed in this paper. According to the model experiments results, the best air injection positon combination is the No.14 and No.11 stations and the best air injection flow rate is 5.5 m 3 /h. Then, for estimating the shaft power, a new similar criteria A m =A s is proposed to ensure the similarity of air film in ship model and full-scale ship. Based on model experiments and CFD simulations, the resistance of the full-scale ship with the optimum air injection condition was predicted. The results show that the air film can produce a power saving of 3%~5% for the ship model and a power saving of 10%~15% for the full-scale ship. INTRODUCTION Over past few decades, the investigation of air lubrication method has been drawing a lot of attention because this method is highly applicable to reduce the friction drag on a ship's surface and very friendly with environment. According to the differences on the physic properties, air lubrication method was divided into three types: air cavity, air film, and small bubble methods (Ceccio, 2010). Kumagai et al. (2015) developed a new power-saving device to reduce friction drag using small bubbles. The results of a series of full-scale tests showed that the new powersaving device could produce a net power saving of 5~15% for ships with correct operation. The air film drag reduction of low-speed ship was investigated based on numerical simulation and model test (Lizheng, 2017; Fan, 2017; Shengqiang, 2017). The research results indicated that the best drag reduction using air film on low-speed ship could reach 15.5% with appropriate air injection flow rates and position. Ye Qing (2015) investigated the implementation of air lubrication on 95000DWT bulk carrier. A model test was carried out and the results showed that the maximum absolute resistance could come to 26.99% at design displacement. Hao Wu (2016) discussed the propulsion performance with air injection for the 95000DWT bulk carrier based on numerical simulations. Hoang (2011) illuminated the effect of bubbles in reducing frictional resistance based on full-scale experiments. Obtained results showed that the resistance reduction in case of ballast condition and full load condition are 11% and 6%, respectively. Elbing (2008) conducted a set of experiments to investigate two distinct drag-reduction phenomena: bubble drag reduction and air-layer drag-reduction. Mizokami (2012) succeeded in applying the air lubrication system to a ship with wide flat bottom surface, and produced about 10% fuel saving. A high-void fraction type of air film was proposed by Mäkiharju (2012). And the usefulness to large tankers was estimated.
Proceedings Papers
Paper presented at the The 28th International Ocean and Polar Engineering Conference, June 10–15, 2018
Paper Number: ISOPE-I-18-192
... been applied in subsea structure monitoring, the cost is rather high and the cycle is very long (Ciria, 2002; Sutherland J, Brampton A, and Whitehouse R, 2006). For that reason, some researchers start to work on model experiment and numerical simulation. The researchers (Whitehouse RJS, 1998; Sumer BM...
Abstract
ABSTRACT The subsea structure layed on the seabed has effect on the current flow in the ocean engineering. The complex current flow disturbs sediment around the subsea structure and scour the structure foundation. If the depth of scour hole is too deep and makes the foundation have uneven settlement, it will affect the structure in regular service even safety and a series of production and environmental problems. The article focus on the scour around the foundation of the subsea production system in South China sea, by using numerical simulation of the sediment transport and deposition using the CFD software and model test. It will provide theoretical basis, model test conclusion and reasonable suggestion for the installation and operation safety in this area. INTRODUCTION In the ocean engineering, the subsea structures laid on the seabed such as gravity anchor, caisson, platform foundation, subsea production system foundation and subsea pipeline have effect on the current flow. The complex current flow disturbs the sediment around the subsea structure and scours the structure foundation. If the scour hole is too deep and makes the uneven settlement of foundation, it may affect the normal use of the structures, even cause safety and a series of production and environmental problems. Therefore, the research on scour of subsea structure foundation becomes very important and necessary. This paper focuses on the scour of the subsea production system foundation in the South China Sea by using numerical simulation. It provides theoretical basis, numerical simulation conclusions and reasonable suggestions for the installation and operation safety in the South China Sea. INVESTIGATION AND RESEACH ON SCOUR OF SUBSEA STRUCTURE Scour is the process of the sediment transport around the subsea foundation caused by current flows and waves. Different types of seabed have different scour characteristics, which can be normally divided into natural developed scour, general scour and local scour (Melville B W and Coleman S E, 2000). The scour of subsea structures mainly caused by local scour and it is considered to be the main reason of the failure of the subsea structures.
Proceedings Papers
Victor Mikhailovich Kozin, Vitaliy Leonidovich Zemlyak, Alexey Sergeevich Vasilyev, Konstantin Igorevich Ipatov
Paper presented at the The 28th International Ocean and Polar Engineering Conference, June 10–15, 2018
Paper Number: ISOPE-I-18-409
... experiments on loading the samples were compared to the numerical results of calculations of ANSYS. KEY WORDS: ferry crossings, surface reinforcement, composite material, ice beam, model experiment, numerical research. INTRODUCTION In winter period in the case of absence of bridge structures or when the...
Abstract
ABSTRACT Practical experience reveals that the physical and mechanical properties of the ice cover can strongly depend on various external factors with using traditional methods of increasing ice resistance. In this connection, the task of increasing the bearing capacity of ice by using alternative methods, for example, the introduction of reinforcing elements into the ice is becoming very relevant. The aim of the work was experimental and numerical study of stress-strain state of ice samples reinforced by surface reinforcing frame. The results of experiments on loading the samples were compared to the numerical results of calculations of ANSYS. INTRODUCTION In winter period in the case of absence of bridge structures or when the arrangement of ferry crossings is impossible the ice crossings arrange when the ice cover of required thickness is formed on the water barriers. If the thickness of the ice cover is not sufficient for the safe operation of the crossing, traditional methods of increasing of ice bearing capacity can be used, such as ice freezing from below, ice frosting from above, or ice strengthening with a wooden cover (Common house needs 218.010–1998). Practical experience reveals that the physical and mechanical properties of the ice cover, strengthened by these methods can strongly depend on various external factors (ambient temperature and presence of snow and wind when freezing). Ice, produced by the accelerated sprinkling method is often a firn mass capable of adhering to the wheels of vehicles and breaking away from the natural ice. This method is effective only for the ice cover of a certain thicknesses, and it increases the probability of formation of deep cracks in the ice. In this connection, the task of increasing the bearing capacity of ice by using alternative methods, for example, the introduction of reinforcing elements into the ice is becoming very relevant. Yakimenko (2015) describes experimental studies on the "surface reinforcement" of ice crossings by geosynthetic materials. Surface reinforcement by freezing the steel meshes was proposed by Nikitin (2015). A number of solutions are known in which steel elements are frozen to increase the bearing capacity in the ice cover (Kostenko, 2005; Kozin, 2003; Kozin, 2011; Kozin, 2012). The method of surface reinforcement by introducing the welded steel frames into the relatively thin ice cover of 0.3–0.4 m thick can actually be sufficiently promising.
Proceedings Papers
Paper presented at the The 27th International Ocean and Polar Engineering Conference, June 25–30, 2017
Paper Number: ISOPE-I-17-391
... settlement, it will affect the structure in regular service even safety and a series of production and environmental problems. The article focus on the scour around the foundation of the subsea production system in the South China Sea, by using model experiment. It will provide theoretical basis, model...
Abstract
ABSTRACT The subsea structures laid on the seabed has effect on the current flow in the ocean engineering. The complex current flow disturbs sediment around the subsea structure and scour the structure foundation. If the depth of scour hole is too deep and makes the foundation have uneven settlement, it will affect the structure in regular service even safety and a series of production and environmental problems. The article focus on the scour around the foundation of the subsea production system in the South China Sea, by using model experiment. It will provide theoretical basis, model experiment conclusion and reasonable suggestion for the installation and operation safety in this area. INTRODUCTION The subsea structures laid on the seabed such as gravity anchor, caisson, platform foundation, subsea production and subsea pipeline has effect on the current flow in ocean engineering. The complex current flow disturbs sediment around the subsea structure and scour the structure foundation. If the depth of scour hole is too deep and makes the foundation have uneven settlement, it will affect the structure in regular service even safety and a series of production and environmental problems. Therefore, the research of scour of subsea structures become very necessary and important. The article focus on the scour around the foundation of the subsea production system in the South China Sea, by using model experiment. It will provide theoretical basis, model experiment conclusion and reasonable suggestion for the installation and operation safety in this area. INVESTIGATION AND RESEACH OF SCOUR OF SUBSEA STRUCTURES Scour is the process of carrying the sand which is caused by the currents and waves. Different seabed has its' own scour characteristics and normally can be divide into naturally developed scour, general scour and local scour. The scour of subsea structures mainly caused by local scour and it is considered to be the main reason of subsea structures' failure.
Proceedings Papers
Paper presented at the The 27th International Ocean and Polar Engineering Conference, June 25–30, 2017
Paper Number: ISOPE-I-17-367
... ABSTRACT This paper presents a parametric study on oscillating water column (OWC) wave energy converter (WEC). The OWC is being planned to be placed on a breakwater in isolated islands remote from the land. Both of numerical analysis and model experiment were utilized for deciding a proper...
Abstract
ABSTRACT This paper presents a parametric study on oscillating water column (OWC) wave energy converter (WEC). The OWC is being planned to be placed on a breakwater in isolated islands remote from the land. Both of numerical analysis and model experiment were utilized for deciding a proper conceptual design that covers the purpose. Various design parameters including configurations and dimensions were evaluated through the numerical analysis, which is based on a potential flow theory, and then several design concepts were selected as candidates. The model experiment using a 2D wave flume was performed to evaluate effects of design parameters and compare performances for the candidates. Based on overall results from the numerical analysis and the model experiment, a conceptual design of the OWC WEC applicable to a breakwater was selected. INTRODUCTION The oscillating water column (OWC), a kind of wave energy converters (WECs), utilizes motions of water column vertically oscillating in the chamber, which produces reciprocating air flow that operates a turbine connected from the chamber by a duct. The OWC WEC has easy maintenance and reliable durability due to its simplicity, so it has been demonstrated commonly in real sea for that reason (Falcao and Henriques, 2016). A first developed large-scale OWC system was Kaimei, installed at western coast of Japan. Eight OWC chambers with capacity of 125kW were equipped on the barge platform, and several turbines had been evaluated on Kaimei (Masuda and McCormick, 1986; Hotta et al., 1988). Another OWC with Wells turbine, capacity of 40kW was deployed into a breakwater located in Sakata port, Japan, in 1990. It was the first case that the OWC was merged into a breakwater, then some cost saving effects were shown (Masuda and McCormick, 1986). In the same year, bottom-fixed OWC with capacity of 125kW was installed at Trivandrum, India. Performance for various turbines including impulse type were evaluated (Mala et al., 2009). In Europe, Pico Plant which is constructed at Pico island, Portugal, with capacity of 400kW has been tested since 1999 (Falcao, 2000), and LIMPET OWC Plant which is deployed at Islay island, Scotland, with capacity of 500kW was evaluated during a real sea test (Heath et al., 2000). In Korea, construction of a bottom-fixed OWC with capacity of 500kW was completed in 2015, and then a real sea test is being prepared.
Proceedings Papers
Paper presented at the The 26th International Ocean and Polar Engineering Conference, June 26–July 2, 2016
Paper Number: ISOPE-I-16-661
... Abstract We propose a deep tow system which consists of a launcher and a towed vehicle to realize high speed towing and good depth and motion control performance of the vehicle. Model experiments were carried out in a towing tank, and interesting results on depth and motion control are shown...
Abstract
Abstract We propose a deep tow system which consists of a launcher and a towed vehicle to realize high speed towing and good depth and motion control performance of the vehicle. Model experiments were carried out in a towing tank, and interesting results on depth and motion control are shown in this paper. Introduction The importance of deep ocean surveying and monitoring is increasing because of the change of situation of energy, oceanic resources and CCS (Carbon Capture and Storage) under the seabed. In recent years, AUVs (Autonomous Underwater Vehicles) have been operated for deep ocean scientific research. However, their long cruising is limited because of their battery performance. Although deep tow systems will solve this problem, the towing speed of current systems is not fast (Homepage of WHOI and JAMSTEC; Greenewalt and Taylor, 1974), and sizable motions are induced by the mother ship. We therefore propose a deep tow system which consists of a launcher and a towed vehicle to achieve high speed towing and good depth and motion control of the vehicle, and have carried out model experiments. In model experiments of a deep tow system, towing cable length cannot be scaled down because of the limitations of depth and length of the tank used. Moreover, the diameter of the cable cannot be scaled down because the power and signal lines in the cable and overall strength must be considered. The main purpose of the model experiments, then, is to make an accurate check of the motion simulator of the deep tow system and to identify an optimal method of controlling the depth and motion of the towed vehicle. If it can be confirmed through these experiments that the accuracy of the simulator is dependable, the reliability of the motion simulations in full scale will be assured.
Proceedings Papers
Paper presented at the The Twenty-fifth International Ocean and Polar Engineering Conference, June 21–26, 2015
Paper Number: ISOPE-I-15-133
... optimize the integrative performance of deep-V monohull. Then tank model experiment was taken to verify the numerical results. The accordance of experiment results with numerical results indicates that integrative performance of deep-V hybrid monohull outperforms the round bilge monohull further...
Abstract
Abstract A kind of high seakeeping performance hidden monohull with deep-V section was proposed based on round bilge monohull and a series of semi-submerged appendages with different shapes and dimensions were designed for it. CFD simulation and STF method with viscous correction were used to optimize the integrative performance of deep-V monohull. Then tank model experiment was taken to verify the numerical results. The accordance of experiment results with numerical results indicates that integrative performance of deep-V hybrid monohull outperforms the round bilge monohull further.
Proceedings Papers
Paper presented at the The Twenty-fifth International Ocean and Polar Engineering Conference, June 21–26, 2015
Paper Number: ISOPE-I-15-643
... beam trawl gear. Numerically analysis and model experiments are carried out to study trawling effect on subsea pipelines. The study focuses on impact and pull-over forces of trawl gear onto the subsea pipeline. Impact and pull- over forces induced by otter trawl gear and beam trawl gear are calculated...
Abstract
Abstract There are busy trawling activities in China Sea. Recently more and more subsea pipelines are laid in this offshore area and most of them are not buried. Trawling activities are high risk for subsea structures especially for unburied subsea pipelines and pipeline damage events exist in this area. It is important to study the trawling effect on subsea pipelines to ensure the safety of them. There are mainly two types of trawling gear in China Sea, otter trawl gear and beam trawl gear. Numerically analysis and model experiments are carried out to study trawling effect on subsea pipelines. The study focuses on impact and pull-over forces of trawl gear onto the subsea pipeline. Impact and pull-over forces induced by otter trawl gear and beam trawl gear are calculated theoretically according to DNV-RP-F111. Meanwhile, model experiments are carried out both in air and underwater to measure the forces. Influences of trawling velocity, fishing equipment type, pipeline span height on impact and pull-over force are studied in model experiment and the results were also compared with the numerical results as verification. Results show that DNV results are generally higher than experimental results. For impact and pull-over force of otter trawl board and beam trawl, there is no significant difference between in air and underwater experiment cases. For all the cases, impact and pull-over forces increase with the increase of trawling velocity. The impact and pull-over forces of otter trawl board increase with the increase of pipeline span height obviously. However, span height doesn't show significant influence on beam trawl impact forces and pull-over forces. Compared with experimental results, DNV-RP-F111 overestimates the force, which is conservative for engineering design, and it will cost more money on the engineering facilities. So it is suggested to consider the DNV rules and the experimental results comprehensively in engineering design.
Proceedings Papers
Paper presented at the The Twenty-fifth International Ocean and Polar Engineering Conference, June 21–26, 2015
Paper Number: ISOPE-I-15-060
... $ % M .A ;06 &6D ( 9 / $ 8 47 L % ! % $ + M 9 4;705 1131 double-hull space model experiment duration time oil leakage sensor resistance-leakage stage tanker enhanced recovery double hull upstream oil & gas...
Abstract
Abstract As submerged oil leakage from damaged tanker is unable to be avoided, a large number of scholars have carried out a series of studies on the mechanism of submerged oil leakage from damaged tank of doublehull tankers based on simplified in-viscid model. With the further research on prediction model of oil leakage and leakage features, viscosity of crude oil has become an essential factor that can't be ignored in improving prediction accuracy. At present, hydro-static and hydrodynamic theory have been applied to the researches on submerged oil leakage from damaged tanker, but the effects of viscosity and turbulence are ignored. Nevertheless, a change in viscosity of oil or the inner structure of double bottom or sloshing leads to significant changes in the behavior of oil leakage, which confirms the presence of viscous effects. This paper presents a study on viscous effects for submerged oil leakage from damaged tank of double-hull tankers. Based on multiphase flow theory and viscous hydrodynamic theory, the mechanism of viscous effects on submerged oil leakage in different leakage stages is explored by the experimental investigation. The presented results are beneficial for a better understanding of viscous effects for submerged oil leakage from damaged tank of double-hull tankers and an emergency control of crude oil leakage from tankers.
Proceedings Papers
Paper presented at the The Twenty-fourth International Ocean and Polar Engineering Conference, June 15–20, 2014
Paper Number: ISOPE-I-14-202
... slope failure infiltration water behavior model slope infiltrate reservoir simulation tensiometer model experiment suction full scale model experiment rainwater water pressure pore water pressure consideration low permeable layer experiment Consideration of Seepage of Rainwater in a...
Abstract
Abstract Slope failure accounts for the majority of sediment disasters due to heavy rain. Both occurrence of seepage flow and pore water pressure in the infinitely long earth slopes are well known causes of slope failure. However, a slope failure could occur in case where the soils in slope might not perfectly be saturated in a full scale model slope experiment. In this paper, the behavior both of rainfall infiltration and pore water pressure in the slope were simulated using a numerical analysis in order to elucidate the cause of slope failure.