Set net fishery is one of the efficient fishery methods and has a history of several centuries in Japan. In 2017, fish harvest amount of set net fishery was 326,200 tons, about 10.2% of the total amount in Japan. The traditional method for harvesting fish is to use two fishing vessels to haul up the box chamber and obtain the fish in it, which requires supplementary equipment and human power. For reducing human power and safety, the automated net-hauling system has been developed. This system used a flexible hose net, with air injected from one side of the hose net, then the net could float up gradually and harvest the fishes. A new hose net was developed by reducing the number of air injection tubes from seven to two in comparison to the previous hose net. The paper presents the results of the animal experiment using 1/60 model of the flexible hose net. The fish-harvest effect in the flow are experimented by the Horizontal Circulating Water Channel. The fish-harvest effect was observed directly. The floating up velocity of the hose net can affect the fish-harvest rate. If the floating up velocity is too fast, the fish are easy to be stuck on the net and cannot swim forward to arrive at the catching spot (trap net). Therefore, the floating up velocity of the hose net not only determines the operational efficiency, but also affects the fish-harvest rate to some extent. Additionally, the deformation of flexible hose net was considered not only during the air injection, but also during the water intrusion.
{"title":"Experimental Study on Fish-Harvest Performance of the Flexible Hose Net","authors":"Qiao Li, Yue Li, Yoichi Mizukami, Shuchuang Dong, Takero Yoshida, D. Kitazawa","doi":"10.1115/omae2020-18513","DOIUrl":"https://doi.org/10.1115/omae2020-18513","url":null,"abstract":"\u0000 Set net fishery is one of the efficient fishery methods and has a history of several centuries in Japan. In 2017, fish harvest amount of set net fishery was 326,200 tons, about 10.2% of the total amount in Japan. The traditional method for harvesting fish is to use two fishing vessels to haul up the box chamber and obtain the fish in it, which requires supplementary equipment and human power. For reducing human power and safety, the automated net-hauling system has been developed. This system used a flexible hose net, with air injected from one side of the hose net, then the net could float up gradually and harvest the fishes. A new hose net was developed by reducing the number of air injection tubes from seven to two in comparison to the previous hose net. The paper presents the results of the animal experiment using 1/60 model of the flexible hose net. The fish-harvest effect in the flow are experimented by the Horizontal Circulating Water Channel. The fish-harvest effect was observed directly. The floating up velocity of the hose net can affect the fish-harvest rate. If the floating up velocity is too fast, the fish are easy to be stuck on the net and cannot swim forward to arrive at the catching spot (trap net). Therefore, the floating up velocity of the hose net not only determines the operational efficiency, but also affects the fish-harvest rate to some extent. Additionally, the deformation of flexible hose net was considered not only during the air injection, but also during the water intrusion.","PeriodicalId":269406,"journal":{"name":"Volume 5: Ocean Space Utilization","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129952273","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Eto, R. Sekiguchi, Hitomi Kashima, T. Ikoma, Y. Aida, K. Masuda
This paper describes the motion characteristics and cargo handling efficiency of the Large-Scale Floating Coal Transshipment Station (LFTS). Indonesia is the main country supplying coal in the Asia-Pacific region, it is important to ensure stable coal supply to Japan. Because the topography of the seabed near East Kalimantan Island, Indonesia’s main coal production area, is shallow, it is difficult for bulk carriers to reach the coast. And then, Large-scale Floating Transposition Station for Loading Coal (hereafter LFTS) was proposed, which will be used as a transposition station between small coal barge coming down the river and bulk carriers stay offshore. By installing LFTS, improvement of coal transport efficiency is expected. As a previous study, the motion characteristics of LFTS using a catenary chain in its mooring system were grasped. However, LFTS can carry up to 500,000 tons of coal, and the draft of LFTS tends to change greatly depending on the coal loading conditions. Besides, the tidal difference in the sea area where the LFTS is installed is about 2 m, and the mounting position of the mooring system on the LFTS side moves up and down by about 10 m at maximum due to changes in the draft and tidal differences. For this reason, when the mounting position of the mooring system is in the lowest state, the mooring line is loosened and the horizontal force is reduced, and it is considered that sufficient restraining force is not exhibited. And, when the mounting position of the mooring system becomes high, the mooring line tension increases and the mooring line may break in some cases. Therefore, in this study, an attempt was made to use an elastic mooring line as a mooring system for LFTS. An elastic mooring line is a mooring line that incorporates a highly stretchable material between mooring lines that connect anchors and floating body. Even if the mooring line attached to the LFTS moves up and down, an appropriate tension always acts on the elastic mooring line, and it can be expected to suppress the oscillation of the floating body and prevent the mooring line from breaking due to excessive tension. However, elastic mooring lines are mainly used for mooring small structures such as piers and aquaculture facilities, but there are no examples where these mooring lines have been applied to structures over 500m like LFTS. Therefore, elastic mooring lines are adopted for the mooring system of LFTS, systematically calculated according to various setting conditions of elastic mooring lines, and it is grasped whether elastic mooring lines can be applied to LFTS, and the motion characteristics of LFTS moored by elastic mooring lines was also grasped.
{"title":"A Fundamental Study on Motion Characteristics of the Large-Scale Floating Coal Transshipment Station by Elastic Mooring Lines","authors":"H. Eto, R. Sekiguchi, Hitomi Kashima, T. Ikoma, Y. Aida, K. Masuda","doi":"10.1115/omae2020-18958","DOIUrl":"https://doi.org/10.1115/omae2020-18958","url":null,"abstract":"\u0000 This paper describes the motion characteristics and cargo handling efficiency of the Large-Scale Floating Coal Transshipment Station (LFTS). Indonesia is the main country supplying coal in the Asia-Pacific region, it is important to ensure stable coal supply to Japan. Because the topography of the seabed near East Kalimantan Island, Indonesia’s main coal production area, is shallow, it is difficult for bulk carriers to reach the coast. And then, Large-scale Floating Transposition Station for Loading Coal (hereafter LFTS) was proposed, which will be used as a transposition station between small coal barge coming down the river and bulk carriers stay offshore. By installing LFTS, improvement of coal transport efficiency is expected.\u0000 As a previous study, the motion characteristics of LFTS using a catenary chain in its mooring system were grasped. However, LFTS can carry up to 500,000 tons of coal, and the draft of LFTS tends to change greatly depending on the coal loading conditions. Besides, the tidal difference in the sea area where the LFTS is installed is about 2 m, and the mounting position of the mooring system on the LFTS side moves up and down by about 10 m at maximum due to changes in the draft and tidal differences. For this reason, when the mounting position of the mooring system is in the lowest state, the mooring line is loosened and the horizontal force is reduced, and it is considered that sufficient restraining force is not exhibited. And, when the mounting position of the mooring system becomes high, the mooring line tension increases and the mooring line may break in some cases.\u0000 Therefore, in this study, an attempt was made to use an elastic mooring line as a mooring system for LFTS. An elastic mooring line is a mooring line that incorporates a highly stretchable material between mooring lines that connect anchors and floating body. Even if the mooring line attached to the LFTS moves up and down, an appropriate tension always acts on the elastic mooring line, and it can be expected to suppress the oscillation of the floating body and prevent the mooring line from breaking due to excessive tension. However, elastic mooring lines are mainly used for mooring small structures such as piers and aquaculture facilities, but there are no examples where these mooring lines have been applied to structures over 500m like LFTS. Therefore, elastic mooring lines are adopted for the mooring system of LFTS, systematically calculated according to various setting conditions of elastic mooring lines, and it is grasped whether elastic mooring lines can be applied to LFTS, and the motion characteristics of LFTS moored by elastic mooring lines was also grasped.","PeriodicalId":269406,"journal":{"name":"Volume 5: Ocean Space Utilization","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129380338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sotaro Masanobu, Satoru Takano, S. Kanada, M. Ono, Hiroki Sasagawa
For subsea mining, it is important to predict the pressure loss in oscillating pipes with pulsating flow for the safe and reliable operation of ore lifting. In the present paper, the authors focused on the pulsating internal flow in static vertical pipe and carried out slurry transport experiment to investigate the effects of flow fluctuation on the pressure loss. The alumina beads and glass beads were used as the solid particles in the experiment, and the fluctuating periods and amplitudes of pulsating water flow were varied. The time-averaged pressure losses calculated by the prediction method for the steady flow proposed in the past by the authors agreed well with the experimental ones. As for the fluctuating component of pressure loss, the calculation results using the quasi-steady expression of a mixture model were compared with the experimental data. The calculated results were different from experimental ones for alumina beads of which densities are almost same as those of the ores of Seafloor Massive Sulfides. It suggests that the expression is insufficient to predict the pressure loss for heavy solid particles. The calculated ones, however, provided those in the safety side. On the other hand, the calculated results for light solid particles such as glass beads agreed well with the experimental ones. It means that the expression would be applicable to the prediction of pressure loss for the mining of manganese nodules which are lighter than the ores of Seafloor Massive Sulfides.
{"title":"Experimental Investigation of Large Particle Slurry Transport in Vertical Pipes With Pulsating Flow","authors":"Sotaro Masanobu, Satoru Takano, S. Kanada, M. Ono, Hiroki Sasagawa","doi":"10.1115/omae2020-18194","DOIUrl":"https://doi.org/10.1115/omae2020-18194","url":null,"abstract":"\u0000 For subsea mining, it is important to predict the pressure loss in oscillating pipes with pulsating flow for the safe and reliable operation of ore lifting. In the present paper, the authors focused on the pulsating internal flow in static vertical pipe and carried out slurry transport experiment to investigate the effects of flow fluctuation on the pressure loss. The alumina beads and glass beads were used as the solid particles in the experiment, and the fluctuating periods and amplitudes of pulsating water flow were varied. The time-averaged pressure losses calculated by the prediction method for the steady flow proposed in the past by the authors agreed well with the experimental ones. As for the fluctuating component of pressure loss, the calculation results using the quasi-steady expression of a mixture model were compared with the experimental data. The calculated results were different from experimental ones for alumina beads of which densities are almost same as those of the ores of Seafloor Massive Sulfides. It suggests that the expression is insufficient to predict the pressure loss for heavy solid particles. The calculated ones, however, provided those in the safety side. On the other hand, the calculated results for light solid particles such as glass beads agreed well with the experimental ones. It means that the expression would be applicable to the prediction of pressure loss for the mining of manganese nodules which are lighter than the ores of Seafloor Massive Sulfides.","PeriodicalId":269406,"journal":{"name":"Volume 5: Ocean Space Utilization","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130822009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
It is of great practical importance to understand the variability of the South China Sea (SCS) monsoon on intraseasonal time scales, since the anomalous enhancement of the SCS monsoon may exert serious impacts on the safety of offshore engineering and marine transportation. Our composite analysis shows that the SCS surface wind anomalies are considerably varying with the Madden-Julian Oscillation (MJO) eastward propagation. The SCS summer southwest monsoon tends to be stronger (weaker) in phases 5–8 (1–4) of MJO with the largest positive (negative) wind-speed anomalies when the MJO convection is centered in the western Pacific (far western Indian Ocean), suggesting the highest (lowest) probability of the gale over the SCS. The variation of the western Pacific Subtropical High (WPSH), induced by the variations of the local meridional circulation, is shown to play a crucial role in the MJO-SCS summer monsoon linkage. The SCS winter monsoon is also shown to be modulated by the MJO with strengthened (weakened) surface northeasterly in phases 5–6 (1–2). The extra-tropical East Asian trough and East Asian westerly jet associated with the local meridional circulation can well explain the changes of the MJO-SCS winter monsoon relationship. The opposite responses of the wind direction during the same phases of the MJO between summer and winter may be attributed to the discrepancy of meridional circulation related to the wintertime equatorward shift of the MJO convection. The present study indicates that the MJO could be taken into consideration when applying extended-range weather forecast over the SCS as the predictability of the MJO activity is up to 15–20 day currently.
{"title":"Impacts of the Madden-Julian Oscillation on South China Sea Monsoon","authors":"Qun Zhou, Lixin Wei","doi":"10.1115/omae2020-19301","DOIUrl":"https://doi.org/10.1115/omae2020-19301","url":null,"abstract":"\u0000 It is of great practical importance to understand the variability of the South China Sea (SCS) monsoon on intraseasonal time scales, since the anomalous enhancement of the SCS monsoon may exert serious impacts on the safety of offshore engineering and marine transportation. Our composite analysis shows that the SCS surface wind anomalies are considerably varying with the Madden-Julian Oscillation (MJO) eastward propagation. The SCS summer southwest monsoon tends to be stronger (weaker) in phases 5–8 (1–4) of MJO with the largest positive (negative) wind-speed anomalies when the MJO convection is centered in the western Pacific (far western Indian Ocean), suggesting the highest (lowest) probability of the gale over the SCS. The variation of the western Pacific Subtropical High (WPSH), induced by the variations of the local meridional circulation, is shown to play a crucial role in the MJO-SCS summer monsoon linkage. The SCS winter monsoon is also shown to be modulated by the MJO with strengthened (weakened) surface northeasterly in phases 5–6 (1–2). The extra-tropical East Asian trough and East Asian westerly jet associated with the local meridional circulation can well explain the changes of the MJO-SCS winter monsoon relationship. The opposite responses of the wind direction during the same phases of the MJO between summer and winter may be attributed to the discrepancy of meridional circulation related to the wintertime equatorward shift of the MJO convection. The present study indicates that the MJO could be taken into consideration when applying extended-range weather forecast over the SCS as the predictability of the MJO activity is up to 15–20 day currently.","PeriodicalId":269406,"journal":{"name":"Volume 5: Ocean Space Utilization","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123703014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Katayama, Yusuke Yamamoto, Taishi Morimoto, M. Goto
The main topics of this paper is the investigation of motion characteristics of the spar-buoy with ring fin motion stabilizer, which is developed to use as a platform for wind observation with a doppler lidar in shallow sea, some mooring conditions to apply it for deep sea. Four different mooring conditions are applied the spar-buoy and it motion in a designed sever wave condition are measured in the towing tank of Osaka Prefecture University. The results show that the amplitude of pitching in deep sea is smaller than the results in shallow sea, even if the wave condition in deep sea are severer than that in shallow sea. From further investigation about the effects of four different mooring conditions on motion characteristics, it has that the center of pitching at four mooring conditions are almost same but the amplitude of pitching is smaller by changing the mooring point and the intermediate sinker position.
{"title":"Motion Characteristics of a Spar-Buoy With Ring-Fin Motion Stabilizer in Deep Sea","authors":"T. Katayama, Yusuke Yamamoto, Taishi Morimoto, M. Goto","doi":"10.1115/omae2020-18595","DOIUrl":"https://doi.org/10.1115/omae2020-18595","url":null,"abstract":"\u0000 The main topics of this paper is the investigation of motion characteristics of the spar-buoy with ring fin motion stabilizer, which is developed to use as a platform for wind observation with a doppler lidar in shallow sea, some mooring conditions to apply it for deep sea. Four different mooring conditions are applied the spar-buoy and it motion in a designed sever wave condition are measured in the towing tank of Osaka Prefecture University.\u0000 The results show that the amplitude of pitching in deep sea is smaller than the results in shallow sea, even if the wave condition in deep sea are severer than that in shallow sea. From further investigation about the effects of four different mooring conditions on motion characteristics, it has that the center of pitching at four mooring conditions are almost same but the amplitude of pitching is smaller by changing the mooring point and the intermediate sinker position.","PeriodicalId":269406,"journal":{"name":"Volume 5: Ocean Space Utilization","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130110972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Satoru Takano, Sotaro Masanobu, J. Yamamoto, S. Kanada, M. Ono, Hiroki Sasagawa
Subsea minerals exist in the deep water within Japanese exclusive economic zone. However, the development of subsea minerals is not commercialized. The Air-lift pump is the promising method for subsea minerals transport. It is significant to estimate the amount of lifting ore when the conditions of submergence ratio and supplying air volume are changed. The estimation of the amount of lifting ore needs the void fraction in three phase flow and friction loss in pipe. Therefore, the empirical methods to estimate the void fraction and friction loss in mainly vertical pipe were proposed in the previous studies. However, the lifting system for subsea minerals has not only vertical pipe but inclined pipe. There are few works for flow assurance on three phase flow in inclined pipe. Then we conducted the scale model experiment to investigate void fraction and friction loss. The experiment was conducted in the conditions of the five kinds of inclination angles. We used the glass beads as solid particles in the experiment. The glass beads were 4mm in diameter and 2553kg/m3 in density. The internal diameter of pipe was 26mm. We applied the empirical method for vertical or horizontal pipe proposed in previous researches to the present experimental condition. Then we compared the experimental results with the calculated ones on void fraction and friction loss. As the results, the calculated results were in good agreement with the experimental ones. Therefore, it was suggested that the void fraction and friction loss in the inclined pipe could be calculated by the empirical method based on the experiment on the vertical or horizontal pipe.
{"title":"Experimental Study on Three Phase Flow in Inclined Pipe for Deep Sea Mining","authors":"Satoru Takano, Sotaro Masanobu, J. Yamamoto, S. Kanada, M. Ono, Hiroki Sasagawa","doi":"10.1115/omae2020-18257","DOIUrl":"https://doi.org/10.1115/omae2020-18257","url":null,"abstract":"\u0000 Subsea minerals exist in the deep water within Japanese exclusive economic zone. However, the development of subsea minerals is not commercialized. The Air-lift pump is the promising method for subsea minerals transport. It is significant to estimate the amount of lifting ore when the conditions of submergence ratio and supplying air volume are changed. The estimation of the amount of lifting ore needs the void fraction in three phase flow and friction loss in pipe. Therefore, the empirical methods to estimate the void fraction and friction loss in mainly vertical pipe were proposed in the previous studies. However, the lifting system for subsea minerals has not only vertical pipe but inclined pipe. There are few works for flow assurance on three phase flow in inclined pipe. Then we conducted the scale model experiment to investigate void fraction and friction loss. The experiment was conducted in the conditions of the five kinds of inclination angles. We used the glass beads as solid particles in the experiment. The glass beads were 4mm in diameter and 2553kg/m3 in density. The internal diameter of pipe was 26mm. We applied the empirical method for vertical or horizontal pipe proposed in previous researches to the present experimental condition. Then we compared the experimental results with the calculated ones on void fraction and friction loss. As the results, the calculated results were in good agreement with the experimental ones. Therefore, it was suggested that the void fraction and friction loss in the inclined pipe could be calculated by the empirical method based on the experiment on the vertical or horizontal pipe.","PeriodicalId":269406,"journal":{"name":"Volume 5: Ocean Space Utilization","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128933215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ryo Nishigochi, H. Eto, K. Iizuka, T. Ikoma, Y. Aida, K. Masuda
Indonesia is the main country supplying coal in the Asia-Pacific region, and in order to secure a stable supply of coal to neighboring countries, efficient coal transportation is required. East Kalimantan Island in Indonesia is the main coal-producing area, but the sea around the island is very shallow and bulk carriers for transporting coal cannot approach the coast. And then, Large-scale Floating Transposition Station for Loading Coal (hereafter LFTS) was proposed, which will be used as a transposition station between small coal barge coming down the river and bulk carriers that stays offshore. LFTS has a two-dimensional extent, and because the bulkheads for separating coal according to quality are installed on the floating body, the rigidity is partially different, and the draft also changes greatly according to the coal loading condition. In this way, LFTS has different characteristics from Mega-Float, which was built in Japan in the late 1990s with the aim of realizing a floating airport, so it is important to clarify its structural characteristics. In order to grasp the stress distribution acting on the structural member in consideration of the influence of the interaction between the overall deformation and the local deformation of LFTS, an analysis in which the entire structure is modeled in detail is desired. However, because members such as the internal bulkheads are arranged in a complicated manner in LFTS, a model in which the entire structure is modeled in detail requires enormous calculation costs in both capacity and time, it is difficult to perform the analysis. In existing research, various models have been studied, but there remains a problem in setting boundary conditions that reproduce the interaction between global and local deformations. And then, in this paper, a new modeling method of LFTS that can be analyzed efficiently was proposed. And the occurrence of stress concentration in the structural members of the LFTS was identified by systematically changing the external force conditions such as the coal loading condition and wave load assumed during the operation of the LFTS, and performing LFTS oscillation analysis and stress deformation analysis. Furthermore, the occurrence of plastic strain due to large deformation was investigated. The stiffening method that efficiently suppresses the occurrence of plastic strain was studied for the locations where the plastic strain was identified by the above analysis. These results demonstrate the importance of modeling large floating structures with complex structures.
{"title":"A Fundamental Study on Plastic Strain Accompanying Deformation in Large-Scale Floating Coal Transshipment Station","authors":"Ryo Nishigochi, H. Eto, K. Iizuka, T. Ikoma, Y. Aida, K. Masuda","doi":"10.1115/omae2020-18962","DOIUrl":"https://doi.org/10.1115/omae2020-18962","url":null,"abstract":"\u0000 Indonesia is the main country supplying coal in the Asia-Pacific region, and in order to secure a stable supply of coal to neighboring countries, efficient coal transportation is required. East Kalimantan Island in Indonesia is the main coal-producing area, but the sea around the island is very shallow and bulk carriers for transporting coal cannot approach the coast. And then, Large-scale Floating Transposition Station for Loading Coal (hereafter LFTS) was proposed, which will be used as a transposition station between small coal barge coming down the river and bulk carriers that stays offshore. LFTS has a two-dimensional extent, and because the bulkheads for separating coal according to quality are installed on the floating body, the rigidity is partially different, and the draft also changes greatly according to the coal loading condition. In this way, LFTS has different characteristics from Mega-Float, which was built in Japan in the late 1990s with the aim of realizing a floating airport, so it is important to clarify its structural characteristics. In order to grasp the stress distribution acting on the structural member in consideration of the influence of the interaction between the overall deformation and the local deformation of LFTS, an analysis in which the entire structure is modeled in detail is desired. However, because members such as the internal bulkheads are arranged in a complicated manner in LFTS, a model in which the entire structure is modeled in detail requires enormous calculation costs in both capacity and time, it is difficult to perform the analysis. In existing research, various models have been studied, but there remains a problem in setting boundary conditions that reproduce the interaction between global and local deformations. And then, in this paper, a new modeling method of LFTS that can be analyzed efficiently was proposed. And the occurrence of stress concentration in the structural members of the LFTS was identified by systematically changing the external force conditions such as the coal loading condition and wave load assumed during the operation of the LFTS, and performing LFTS oscillation analysis and stress deformation analysis. Furthermore, the occurrence of plastic strain due to large deformation was investigated. The stiffening method that efficiently suppresses the occurrence of plastic strain was studied for the locations where the plastic strain was identified by the above analysis. These results demonstrate the importance of modeling large floating structures with complex structures.","PeriodicalId":269406,"journal":{"name":"Volume 5: Ocean Space Utilization","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130889647","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An autonomous underwater vehicle (AUV) equipped with some navigational devices, such as an inertial navigation system (INS), a Doppler velocity log (DVL), and a depth sensor. This integrated system is typical and accurate, however, have drift error in position output. Then an acoustic positioning, which is one of absolute positioning, is necessary to compensate the drift error. As acoustic positioning, ultra-short baseline (USBL) is frequently used, however, not accurate especially in deep water. Long baseline (LBL) is very accurate, however, spends much time to operate. In this paper, acoustic positioning method of AUV based on ranging from only one reference device is considered with simulations. One-way travel time (OWTT) is measured for ranging assuming use of chip scale atomic clock (CSAC). And the ranging signal is continuous and modulated direct sequence spread spectrum (DSSS). Ranging is executed at each symbol peak, then period of the ranging is very small. In process of the method, the drift error of position output of the INS is estimated with extended Kalman filter (EKF). Simulation with two models, constant-position-error, and constant-velocity-error models, were performed. The later was obviously unstable. Circular cruising track of the A UV makes the estimation more stable. Moreover, when the AUV cruises near the reference, the estimation is more stable. It may good that at final phase of descending of the AUV, the AUV cruises near the seabed and spirally, and the estimation process may be performed stably.
{"title":"Basic Study on Positioning of Autonomous Underwater Vehicle Based on Acoustic Ranging From One Reference Device","authors":"Yoshitaka Watanabe","doi":"10.1115/omae2020-19105","DOIUrl":"https://doi.org/10.1115/omae2020-19105","url":null,"abstract":"\u0000 An autonomous underwater vehicle (AUV) equipped with some navigational devices, such as an inertial navigation system (INS), a Doppler velocity log (DVL), and a depth sensor. This integrated system is typical and accurate, however, have drift error in position output. Then an acoustic positioning, which is one of absolute positioning, is necessary to compensate the drift error. As acoustic positioning, ultra-short baseline (USBL) is frequently used, however, not accurate especially in deep water. Long baseline (LBL) is very accurate, however, spends much time to operate. In this paper, acoustic positioning method of AUV based on ranging from only one reference device is considered with simulations. One-way travel time (OWTT) is measured for ranging assuming use of chip scale atomic clock (CSAC). And the ranging signal is continuous and modulated direct sequence spread spectrum (DSSS). Ranging is executed at each symbol peak, then period of the ranging is very small. In process of the method, the drift error of position output of the INS is estimated with extended Kalman filter (EKF). Simulation with two models, constant-position-error, and constant-velocity-error models, were performed. The later was obviously unstable. Circular cruising track of the A UV makes the estimation more stable. Moreover, when the AUV cruises near the reference, the estimation is more stable. It may good that at final phase of descending of the AUV, the AUV cruises near the seabed and spirally, and the estimation process may be performed stably.","PeriodicalId":269406,"journal":{"name":"Volume 5: Ocean Space Utilization","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130769649","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Aviation has a significant impact on the global emission of greenhouse gasses. On the Northern Atlantic route alone there are over 2,500 crossings daily. This illustrates the high demand for connecting people. It is expected that this demand will only increase in the future, which will increase the emissions due to aviation even further. An alternative way for connecting people can be the hyperloop, which obtains comparable speeds while using a fraction of the energy. For intercontinental connections a tunnel would be necessary. In this study, a conceptual design of a mid-water floating hyperloop tunnel is made and tested on model scale at MARIN. In the present paper the results are discussed of model tests on a mid-water floating tunnel in Atlantic storm conditions at various wave directions and tunnel depths. The conceptual design of the tunnel is based on (nearly) available technology. One kilometer tunnel segments with a diameter of 11 m are connected to construct a tunnel length of > 5,000 km. Model basin tests are performed on scale 1:110, where a scale model of 140 m length is tested. The tunnel is designed as a neutral buoyant tunnel to reduce complexity and costs for the mooring system. The motions, deformations and mooring line tensions for the tunnel segments are measured by force transducers, accelerometers and an optical measurement system. Due to flexibility of the slender tunnel segments in combination with a soft mooring system, the tunnel tends to following the incoming waves for certain tunnel depths and wave directions. Only small motions and deformations are allowed for a hyperloop capsule to travel on high speed. The conceptual tests show first results on tunnel depth, structural and geometrical design of an hyperloop tunnel and mooring system.
{"title":"Conceptual Design and Model Tests for a Mid-Water Floating Hyperloop Tunnel","authors":"L. Kemp, W. Otto, O. Waals","doi":"10.1115/omae2020-18785","DOIUrl":"https://doi.org/10.1115/omae2020-18785","url":null,"abstract":"\u0000 Aviation has a significant impact on the global emission of greenhouse gasses. On the Northern Atlantic route alone there are over 2,500 crossings daily. This illustrates the high demand for connecting people. It is expected that this demand will only increase in the future, which will increase the emissions due to aviation even further. An alternative way for connecting people can be the hyperloop, which obtains comparable speeds while using a fraction of the energy. For intercontinental connections a tunnel would be necessary.\u0000 In this study, a conceptual design of a mid-water floating hyperloop tunnel is made and tested on model scale at MARIN. In the present paper the results are discussed of model tests on a mid-water floating tunnel in Atlantic storm conditions at various wave directions and tunnel depths.\u0000 The conceptual design of the tunnel is based on (nearly) available technology. One kilometer tunnel segments with a diameter of 11 m are connected to construct a tunnel length of > 5,000 km. Model basin tests are performed on scale 1:110, where a scale model of 140 m length is tested. The tunnel is designed as a neutral buoyant tunnel to reduce complexity and costs for the mooring system. The motions, deformations and mooring line tensions for the tunnel segments are measured by force transducers, accelerometers and an optical measurement system.\u0000 Due to flexibility of the slender tunnel segments in combination with a soft mooring system, the tunnel tends to following the incoming waves for certain tunnel depths and wave directions. Only small motions and deformations are allowed for a hyperloop capsule to travel on high speed. The conceptual tests show first results on tunnel depth, structural and geometrical design of an hyperloop tunnel and mooring system.","PeriodicalId":269406,"journal":{"name":"Volume 5: Ocean Space Utilization","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126715374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Takaaki Takeuchi, T. Utsunomiya, K. Gotoh, I. Sato
For reducing the maintenance cost of floating offshore wind turbine structures, it is necessary to establish a quantitative wear estimation method for the mooring chains. In this paper, attempts have been made to improve the accuracy of the estimation method in terms of the mooring chain model. These investigations were performed about a spar-type floater moored with three catenary mooring lines at Goto, Nagasaki prefecture, Japan. Up to now, the mass-spring model had been used for the mooring chain in response analysis and the relative angle between two spring lines was considered as only a sliding angle without friction. However, there is also rolling in the motion between mooring links, which should cause less wear than by sliding. In this study, the detailed motion of the link in response analysis is calculated and applied to the wear estimation by using a 3-D model in MSC. Adams. This enables the wear estimation considering link motion closer to a real phenomenon. A Contact analysis between the 3-D chain model requires some contact properties (e.g. contact stiffness and friction). In this paper, these properties are calculated based on the Hertzian contact method and FEM analysis. As a result, the wear amounts overestimated by using the mass-spring model in the previous investigation, especially at the point located clump weight and touchdown point, decrease getting closer to the measurements. In addition, by tracking the contact points it is found that the major motion caused between links is the rolling. For future works, there remains a need for further validation and the consideration of elasticity between mooring links, impressions caused by proof load test and the effect of corrosion.
{"title":"Quantitative Wear Estimation for Floating Structures by Using 3-D Geometry of Mooring Chain","authors":"Takaaki Takeuchi, T. Utsunomiya, K. Gotoh, I. Sato","doi":"10.1115/omae2020-18409","DOIUrl":"https://doi.org/10.1115/omae2020-18409","url":null,"abstract":"\u0000 For reducing the maintenance cost of floating offshore wind turbine structures, it is necessary to establish a quantitative wear estimation method for the mooring chains. In this paper, attempts have been made to improve the accuracy of the estimation method in terms of the mooring chain model. These investigations were performed about a spar-type floater moored with three catenary mooring lines at Goto, Nagasaki prefecture, Japan.\u0000 Up to now, the mass-spring model had been used for the mooring chain in response analysis and the relative angle between two spring lines was considered as only a sliding angle without friction. However, there is also rolling in the motion between mooring links, which should cause less wear than by sliding. In this study, the detailed motion of the link in response analysis is calculated and applied to the wear estimation by using a 3-D model in MSC. Adams. This enables the wear estimation considering link motion closer to a real phenomenon. A Contact analysis between the 3-D chain model requires some contact properties (e.g. contact stiffness and friction). In this paper, these properties are calculated based on the Hertzian contact method and FEM analysis.\u0000 As a result, the wear amounts overestimated by using the mass-spring model in the previous investigation, especially at the point located clump weight and touchdown point, decrease getting closer to the measurements. In addition, by tracking the contact points it is found that the major motion caused between links is the rolling. For future works, there remains a need for further validation and the consideration of elasticity between mooring links, impressions caused by proof load test and the effect of corrosion.","PeriodicalId":269406,"journal":{"name":"Volume 5: Ocean Space Utilization","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124192823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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