This paper aims to assess the marine space availability for the nearshore and offshore wave energy exploration while avoiding conflict with any technical, environmental, legal or other use restriction. Within the available areas retrieved in a GIS environment, it is presented a method to evaluate the performance of various state-of-the-art Wave Energy Converter technologies in terms of the expected Power Output Capacity Factor and Capture Width, when potentially working in the characteristic sea states found on the selected areas. The method is applied to a case study in the Archipelago of Azores. The data of the wave resource utilized comes from a hindcast model refined down to a spatial resolution of 0.05° that makes possible the detailed analysis and spatial comparison of results at insular local scales. The results intend to provide stakeholders and decision-makers with meaningful information about the suitable locations for the wave energy exploration and about the most efficient converter devices in such locations for the potential deployment of a wave energy exploration facility.
{"title":"A Method for Identifying Compatible Locations for Wave Energy Exploration With Different WECs","authors":"S. Ramos, M. Gonçalves, C. Guedes Soares","doi":"10.1115/omae2021-62949","DOIUrl":"https://doi.org/10.1115/omae2021-62949","url":null,"abstract":"\u0000 This paper aims to assess the marine space availability for the nearshore and offshore wave energy exploration while avoiding conflict with any technical, environmental, legal or other use restriction. Within the available areas retrieved in a GIS environment, it is presented a method to evaluate the performance of various state-of-the-art Wave Energy Converter technologies in terms of the expected Power Output Capacity Factor and Capture Width, when potentially working in the characteristic sea states found on the selected areas. The method is applied to a case study in the Archipelago of Azores. The data of the wave resource utilized comes from a hindcast model refined down to a spatial resolution of 0.05° that makes possible the detailed analysis and spatial comparison of results at insular local scales. The results intend to provide stakeholders and decision-makers with meaningful information about the suitable locations for the wave energy exploration and about the most efficient converter devices in such locations for the potential deployment of a wave energy exploration facility.","PeriodicalId":269406,"journal":{"name":"Volume 5: Ocean Space Utilization","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114834085","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. Fujiwara, Kangsoo Kim, M. Sasano, Takumi Sato, Shogo Inaba, Akihiro Okamoto, Motonobu Imasato, H. Osawa
In the 2nd term SIP project (SIP2), “Innovative Technology for Exploration of Deep Sea Resources” in Japan, National Maritime Research Institute, NMRI, is promoting the AUVs control system construction initiatively together with the leading agency, Japan Agency for Marine-Earth Science and Technology, JAMSTEC. To promote future high-level formation control, two types of fundamental formation control tests were tried using two AUVs and one ASV in the sea. One of them is virtual leader-follower control, and the other is centralized AUV control by one ASV. Seafloor topography mapping at the coast in Japan was successfully conducted by the two control methods with AUVs as test trials. In this paper, the results of the fundamental formation control tests of them are reported and summarized. Detailed consideration of the test results is represented using a simple simulation of AUVs in the latter half of this paper. Moreover, the plan for the promotion of the formation control system that will be done in near future is introduced.
{"title":"Sea Trials Summarization on Fundamental Formation Control of Multiple Cruising AUVs","authors":"T. Fujiwara, Kangsoo Kim, M. Sasano, Takumi Sato, Shogo Inaba, Akihiro Okamoto, Motonobu Imasato, H. Osawa","doi":"10.1115/omae2021-61483","DOIUrl":"https://doi.org/10.1115/omae2021-61483","url":null,"abstract":"\u0000 In the 2nd term SIP project (SIP2), “Innovative Technology for Exploration of Deep Sea Resources” in Japan, National Maritime Research Institute, NMRI, is promoting the AUVs control system construction initiatively together with the leading agency, Japan Agency for Marine-Earth Science and Technology, JAMSTEC. To promote future high-level formation control, two types of fundamental formation control tests were tried using two AUVs and one ASV in the sea. One of them is virtual leader-follower control, and the other is centralized AUV control by one ASV. Seafloor topography mapping at the coast in Japan was successfully conducted by the two control methods with AUVs as test trials.\u0000 In this paper, the results of the fundamental formation control tests of them are reported and summarized. Detailed consideration of the test results is represented using a simple simulation of AUVs in the latter half of this paper. Moreover, the plan for the promotion of the formation control system that will be done in near future is introduced.","PeriodicalId":269406,"journal":{"name":"Volume 5: Ocean Space Utilization","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125477042","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}
When a large-scale tsunami occurs, structures in the coastal area will be destroyed by the impact of tsunami drifts. In the design of tsunami evacuation facilities and petroleum complexes, it is necessary to estimate the impact force of tsunami drift, which varies in size, shape and mass. Although some design equations have been proposed to estimate the impact force of tsunami drift, the impact force varies depending on various conditions such as the draft of the tsunami drifts, the attitude of the collision, the condition of the surrounding flow field, and the rigidity of the structure, etc. No reasonable design equation has been developed yet to meet all these conditions. Therefore, it is necessary to estimate the impact force of tsunami drift by water tank experiments and numerical simulations. In order to simulate the impact of a tsunami drift on a structure by numerical simulation, it is necessary to solve the coupling of fluid, floating object and structure. In this study, we have developed a simulation system that can simulate the impact force of a tsunami drift with the MPS method, which is a kind of particle method. This simulation system introduces an explicit method for pressure calculation, which allows for relatively large scale numerical calculations. In addition, the system is able to reproduce the deformation of structures as an elastic body due to the impact of tsunami drift. In particular, we have introduced an analytical method that allows us to set the computational time step that satisfy the CFL conditions for elastic and fluid particles, respectively, for stable simulation even when there is a large difference between the velocity of fluid particles and the velocity of structural particles caused by elastic waves. As a result of the comparison of the impact force on the cantilevered beam of the tsunami drift with the simulation and the water tank test, the deformation of the structure at the time of impact was reproduced with more than 90% accuracy.
{"title":"Development of a Simulation System for Estimating the Impact Force of Tsunami Drift Using the Explicit MPS Method","authors":"Y. Aida, T. Ikoma, K. Masuda","doi":"10.1115/omae2021-62244","DOIUrl":"https://doi.org/10.1115/omae2021-62244","url":null,"abstract":"\u0000 When a large-scale tsunami occurs, structures in the coastal area will be destroyed by the impact of tsunami drifts. In the design of tsunami evacuation facilities and petroleum complexes, it is necessary to estimate the impact force of tsunami drift, which varies in size, shape and mass. Although some design equations have been proposed to estimate the impact force of tsunami drift, the impact force varies depending on various conditions such as the draft of the tsunami drifts, the attitude of the collision, the condition of the surrounding flow field, and the rigidity of the structure, etc. No reasonable design equation has been developed yet to meet all these conditions. Therefore, it is necessary to estimate the impact force of tsunami drift by water tank experiments and numerical simulations. In order to simulate the impact of a tsunami drift on a structure by numerical simulation, it is necessary to solve the coupling of fluid, floating object and structure. In this study, we have developed a simulation system that can simulate the impact force of a tsunami drift with the MPS method, which is a kind of particle method. This simulation system introduces an explicit method for pressure calculation, which allows for relatively large scale numerical calculations. In addition, the system is able to reproduce the deformation of structures as an elastic body due to the impact of tsunami drift. In particular, we have introduced an analytical method that allows us to set the computational time step that satisfy the CFL conditions for elastic and fluid particles, respectively, for stable simulation even when there is a large difference between the velocity of fluid particles and the velocity of structural particles caused by elastic waves. As a result of the comparison of the impact force on the cantilevered beam of the tsunami drift with the simulation and the water tank test, the deformation of the structure at the time of impact was reproduced with more than 90% accuracy.","PeriodicalId":269406,"journal":{"name":"Volume 5: Ocean Space Utilization","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133793232","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}
Marine renewable energy is expected as an alternative energy source to fossil fuel. Wave energy is one of the marine renewable energy. The subject of this paper is maximizing power generation by a Point Absorber Wave Energy Converters (PA-WEC) in irregular waves. In the previous study on maximizing the power generation by one of the authors, it has been shown the theoretical solution of the time-domain control force in irregular waves which are defined by superposing regular waves components. That is, if the PA-WEC can simultaneously understand the irregular incident waves as multi certain regular wave components, it can be decided the control force for maximizing the power generation. On the other hand, it is quite difficult to predict precisely and simultaneously the component of coming irregular waves to a PA-WEC installed in the ocean. In the recent, Artificial Intelligence (AI) and machine learning technology progress rapidly. In the machine learning system, because reading huge data with the relation among them, sometimes it finds out the path connecting A matter and B matter without visible theoretical or logical relations. In this case, the quality of a training data is quite important for accuracy or certainty of the efficient prediction. In this paper, we examine the possibility of applying AI to predict and decide the control force for maximizing the power generation of the PA-WEC in irregular waves. Some of the results given by the AI has been quite close to the theoretical answer in irregular waves. Through the examination, we investigate and discuss the best or the effective combination of training data sets which are based on the theoretical situation in known waves.
{"title":"The Fundamental Research on AI Prediction and Determination of Control Force for Maximizing the Power Generation of PA-WEC in Irregular Waves","authors":"M. Murai, Shotaro Sakamoto","doi":"10.1115/omae2021-61493","DOIUrl":"https://doi.org/10.1115/omae2021-61493","url":null,"abstract":"\u0000 Marine renewable energy is expected as an alternative energy source to fossil fuel. Wave energy is one of the marine renewable energy. The subject of this paper is maximizing power generation by a Point Absorber Wave Energy Converters (PA-WEC) in irregular waves. In the previous study on maximizing the power generation by one of the authors, it has been shown the theoretical solution of the time-domain control force in irregular waves which are defined by superposing regular waves components. That is, if the PA-WEC can simultaneously understand the irregular incident waves as multi certain regular wave components, it can be decided the control force for maximizing the power generation. On the other hand, it is quite difficult to predict precisely and simultaneously the component of coming irregular waves to a PA-WEC installed in the ocean.\u0000 In the recent, Artificial Intelligence (AI) and machine learning technology progress rapidly. In the machine learning system, because reading huge data with the relation among them, sometimes it finds out the path connecting A matter and B matter without visible theoretical or logical relations. In this case, the quality of a training data is quite important for accuracy or certainty of the efficient prediction.\u0000 In this paper, we examine the possibility of applying AI to predict and decide the control force for maximizing the power generation of the PA-WEC in irregular waves. Some of the results given by the AI has been quite close to the theoretical answer in irregular waves. Through the examination, we investigate and discuss the best or the effective combination of training data sets which are based on the theoretical situation in known waves.","PeriodicalId":269406,"journal":{"name":"Volume 5: Ocean Space Utilization","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115212590","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}
Saika Iwamatsu, Y. Nihei, K. Iijima, T. Ikoma, Tomoki Komori
In this study, a series of dedicated water tank tests were conducted in wind and waves to investigate the stability performance and turning motion of Floating Offshore Wind Turbine (FOWT) equipped with two vertical axis wind turbines (VAWT). The FOWT targeted in this study is called Multi-connection VAWT, which is a new type of FOWT moored by Single-Point-Mooring (SPM) system. We designed and manufactured two types of semi-submersible floating bodies. One is a type in which VAWTs are mounted in two places of a right-angled isosceles triangle (Type-A) on a single floater, and the other is two independent units equipped with VAWTs on two separate floaters centered on a moored body. This is a type in which two semi-submersible floating bodies are lined up in a straight line (Type-B). The experimental conditions were determined by scaling down to 1/100 using Froude’s scaling law based on a wind thrust load of 320 kN (rated wind speed of 12 m/s) assuming an actual machine. In the free yawing test in waves, Type-A turned downwards, while Type-B was barely affected by the waves. Furthermore, in the free yawing test in wind, both Type-A and Type-B turned leeward and stabilized at a final point where the wind load was balanced.
{"title":"Experimental Study on the Stability Performance and Turning Motion of Multi-Connection VAWT","authors":"Saika Iwamatsu, Y. Nihei, K. Iijima, T. Ikoma, Tomoki Komori","doi":"10.1115/omae2021-62662","DOIUrl":"https://doi.org/10.1115/omae2021-62662","url":null,"abstract":"\u0000 In this study, a series of dedicated water tank tests were conducted in wind and waves to investigate the stability performance and turning motion of Floating Offshore Wind Turbine (FOWT) equipped with two vertical axis wind turbines (VAWT). The FOWT targeted in this study is called Multi-connection VAWT, which is a new type of FOWT moored by Single-Point-Mooring (SPM) system. We designed and manufactured two types of semi-submersible floating bodies. One is a type in which VAWTs are mounted in two places of a right-angled isosceles triangle (Type-A) on a single floater, and the other is two independent units equipped with VAWTs on two separate floaters centered on a moored body. This is a type in which two semi-submersible floating bodies are lined up in a straight line (Type-B). The experimental conditions were determined by scaling down to 1/100 using Froude’s scaling law based on a wind thrust load of 320 kN (rated wind speed of 12 m/s) assuming an actual machine. In the free yawing test in waves, Type-A turned downwards, while Type-B was barely affected by the waves. Furthermore, in the free yawing test in wind, both Type-A and Type-B turned leeward and stabilized at a final point where the wind load was balanced.","PeriodicalId":269406,"journal":{"name":"Volume 5: Ocean Space Utilization","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122320402","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}
Shuchuang Dong, Sang-gyu Park, Jinxin Zhou, Qiao Li, Takero Yoshida, D. Kitazawa
The interaction between fluid and fish cage with stocked fish is extremely complex, including fluid and structure, as well as fluid and fish swimming behavior. The on-current swimming pattern of fish schools was found toward the incoming flow in the previous laboratory studies, which is different from the circular swimming pattern commonly observed in the farming site. In this study, a pseudo fish school structure model (PFS) was proposed to reproduce the five circular swimming patterns of farmed yellowtail, and to investigate the influence of fish school behaviors on the flow field inside and around a model square fish cage in laboratory experiments. The results showed that the drag force acting on the square fish cage increased with the increase of the current speed for all fish school swimming patterns, but no clear difference was observed between the fish school swimming behavior patterns. Overall, the drag force of the square fish cage considering the farmed fish behavior decreased by 11.8%, compared to the drag force of the fish cage without PFS. The current speeds inside and downstream of the fish cage increased almost linearly with increasing current velocities. Compared with the case of the fish cage without PFS, the current speed inside the cage under motionless closely PFS (C0), revolving closely PFS (CR), motionless loosely PFS (L0) and revolving loosely PFS (LR) conditions changed by 10.8%, 9.4%, 65.8% and 39.7%, respectively. In addition, compared to the case of the fish cage without PFS, the current speeds under C0, CR, L0 and LR conditions decreased by 89.8%, 16.3%, 58.2%, and 31.9%, respectively, at 16.0cm downstream from the fish cage, and decreased by 69.2%, 19.4%, 62.7% and 26.3%, respectively, at 63.6cm downstream from the fish cage. Furthermore, the current speed distribution and relative horizontal turbulence intensity distribution inside and around the fish cage under different fish school swimming pattern was discussed. In the future, we will use live fish to conduct experiments to evaluate fish school models.
{"title":"Flow Field Inside and Around a Square Fish Cage Considering Fish School Swimming Pattern","authors":"Shuchuang Dong, Sang-gyu Park, Jinxin Zhou, Qiao Li, Takero Yoshida, D. Kitazawa","doi":"10.1115/omae2021-63047","DOIUrl":"https://doi.org/10.1115/omae2021-63047","url":null,"abstract":"\u0000 The interaction between fluid and fish cage with stocked fish is extremely complex, including fluid and structure, as well as fluid and fish swimming behavior. The on-current swimming pattern of fish schools was found toward the incoming flow in the previous laboratory studies, which is different from the circular swimming pattern commonly observed in the farming site. In this study, a pseudo fish school structure model (PFS) was proposed to reproduce the five circular swimming patterns of farmed yellowtail, and to investigate the influence of fish school behaviors on the flow field inside and around a model square fish cage in laboratory experiments.\u0000 The results showed that the drag force acting on the square fish cage increased with the increase of the current speed for all fish school swimming patterns, but no clear difference was observed between the fish school swimming behavior patterns. Overall, the drag force of the square fish cage considering the farmed fish behavior decreased by 11.8%, compared to the drag force of the fish cage without PFS. The current speeds inside and downstream of the fish cage increased almost linearly with increasing current velocities. Compared with the case of the fish cage without PFS, the current speed inside the cage under motionless closely PFS (C0), revolving closely PFS (CR), motionless loosely PFS (L0) and revolving loosely PFS (LR) conditions changed by 10.8%, 9.4%, 65.8% and 39.7%, respectively. In addition, compared to the case of the fish cage without PFS, the current speeds under C0, CR, L0 and LR conditions decreased by 89.8%, 16.3%, 58.2%, and 31.9%, respectively, at 16.0cm downstream from the fish cage, and decreased by 69.2%, 19.4%, 62.7% and 26.3%, respectively, at 63.6cm downstream from the fish cage. Furthermore, the current speed distribution and relative horizontal turbulence intensity distribution inside and around the fish cage under different fish school swimming pattern was discussed. In the future, we will use live fish to conduct experiments to evaluate fish school models.","PeriodicalId":269406,"journal":{"name":"Volume 5: Ocean Space Utilization","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122120388","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}
Multi-Criteria Decision Methods (MCDM) as a complement to current practices for identifying an initial compromise solution to the problem of wind turbine micro-siting are proposed. MCDM deals with multiple objectives in decision-making. The main goal of these methods is to choose among several alternatives using decision criteria previously defined. The use of MCDM guarantees the identification of the alternative that better performs than all the others according to the selected criteria. After a literature review on available methods for micro-siting of offshore wind turbines in a specific location, and an introduction to the MCDM, the usefulness and potential of MCDM in siting floating wind turbines is highlighted. The MCDM methods can add new parameters to the floating wind farms’ layout process. The results of this study support the potential role of these methods as crucial tools to technology developers and decision-makers.
{"title":"Micro-Siting of Floating Turbines Through Multiple-Criteria Decision-Making","authors":"H. Díaz, C. Guedes Soares","doi":"10.1115/omae2021-63752","DOIUrl":"https://doi.org/10.1115/omae2021-63752","url":null,"abstract":"\u0000 Multi-Criteria Decision Methods (MCDM) as a complement to current practices for identifying an initial compromise solution to the problem of wind turbine micro-siting are proposed. MCDM deals with multiple objectives in decision-making. The main goal of these methods is to choose among several alternatives using decision criteria previously defined. The use of MCDM guarantees the identification of the alternative that better performs than all the others according to the selected criteria. After a literature review on available methods for micro-siting of offshore wind turbines in a specific location, and an introduction to the MCDM, the usefulness and potential of MCDM in siting floating wind turbines is highlighted. The MCDM methods can add new parameters to the floating wind farms’ layout process. The results of this study support the potential role of these methods as crucial tools to technology developers and decision-makers.","PeriodicalId":269406,"journal":{"name":"Volume 5: Ocean Space Utilization","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129277101","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, S. Kanada, Masao Ono
Subsea minerals exist in the deep water within Japan’s exclusive economic zone. There are many technical issues which should be addressed for subsea mining. The air-lift pumping systems are one of promising methods for subsea minerals transport. Flow assurance for three-phase flow is important to design the air-lift pumping system for subsea mining. It is important to establish methods for estimating void fractions and frictional pressure drops. To establish the methods for three-phase flow, we reviewed previous studies for two- or three-phase flow. There are some models to estimate the void fractions such as slip flow model and drift flux model. There are also some models to estimate the frictional pressure drops such as homogeneous model and separated flow model. We calculated void fractions and frictional pressure drops by existing correlation and compared calculated results with experimental data in two- or three-phase flow. In addition, we proposed the methods for estimating the void fractions and frictional pressure drops in three-phase flow. These had fewer number of experimental constants than existing correlations, these could calculate void fractions and frictional pressure drops in more various conditions than existing correlations.
{"title":"Experimental Study on Void Fractions and Pressure Drops in Three-Phase Flow for Deep Sea Mining","authors":"Satoru Takano, Sotaro Masanobu, S. Kanada, Masao Ono","doi":"10.1115/omae2021-60472","DOIUrl":"https://doi.org/10.1115/omae2021-60472","url":null,"abstract":"\u0000 Subsea minerals exist in the deep water within Japan’s exclusive economic zone. There are many technical issues which should be addressed for subsea mining.\u0000 The air-lift pumping systems are one of promising methods for subsea minerals transport. Flow assurance for three-phase flow is important to design the air-lift pumping system for subsea mining. It is important to establish methods for estimating void fractions and frictional pressure drops.\u0000 To establish the methods for three-phase flow, we reviewed previous studies for two- or three-phase flow. There are some models to estimate the void fractions such as slip flow model and drift flux model. There are also some models to estimate the frictional pressure drops such as homogeneous model and separated flow model. We calculated void fractions and frictional pressure drops by existing correlation and compared calculated results with experimental data in two- or three-phase flow.\u0000 In addition, we proposed the methods for estimating the void fractions and frictional pressure drops in three-phase flow. These had fewer number of experimental constants than existing correlations, these could calculate void fractions and frictional pressure drops in more various conditions than existing correlations.","PeriodicalId":269406,"journal":{"name":"Volume 5: Ocean Space Utilization","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127352829","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}
Y. Gai, Shuang‐Xi Guo, Yilun Li, Min Li, Weimin Chen
Deep-sea minerals such as polymetallic nodule, hydrothermal sulphides and ferro-manganese crusts have for long attracted attention as an alternative source of metals to terrestrial deposits. To bring these minerals up to the land, flexible risers are needed. As the mining industry developing towards deep sea area, the conveying system is usually designed as a combination of steel riser and flexible riser. According to different transport requirements, various flexible riser configurations, such as steel catenary riser, lazy-wave riser and saddle-shaped riser, have been proposed. During mining operation, the riser bears gravity, buoyancy, wave and current force, therefore the assessment of structural safety and reliability is quite challenging. In addition, the riser response caused by the mining vehicle motion during working process in a large area should also be considered. To guarantee a safe operation and service life of the riser, it is necessary to carefully design its configuration and to analyze its performance. In this study, taking the saddle-shaped riser as our model, the influences of main design parameters on the riser configuration, tension and stress are examined. These parameters include the installation position of buoyancy modules, the buoyancy ratio and motion of mining vehicle. Firstly, the analysis model of the riser response is established based on FEM in which the nonlinear large displacement and deformation of the structure are considered. Secondly, through our FEM simulation, the distribution and variation of tension and stress along the axial length of risers with different configurations are presented. Finally, the impacts of the mining vehicle motion on riser response are discussed. Our numerical results show that a small change of the buoyancy position and buoyancy ratio may lead to a significant change of the riser configuration, but a little change of riser tension/stress. And the saddle-shaped riser has a good tolerance performance to the bottom-end excitation.
{"title":"Configuration and Performance Analysis of Deep Ocean Mining Flexible Riser","authors":"Y. Gai, Shuang‐Xi Guo, Yilun Li, Min Li, Weimin Chen","doi":"10.1115/omae2020-18346","DOIUrl":"https://doi.org/10.1115/omae2020-18346","url":null,"abstract":"\u0000 Deep-sea minerals such as polymetallic nodule, hydrothermal sulphides and ferro-manganese crusts have for long attracted attention as an alternative source of metals to terrestrial deposits. To bring these minerals up to the land, flexible risers are needed. As the mining industry developing towards deep sea area, the conveying system is usually designed as a combination of steel riser and flexible riser. According to different transport requirements, various flexible riser configurations, such as steel catenary riser, lazy-wave riser and saddle-shaped riser, have been proposed. During mining operation, the riser bears gravity, buoyancy, wave and current force, therefore the assessment of structural safety and reliability is quite challenging. In addition, the riser response caused by the mining vehicle motion during working process in a large area should also be considered. To guarantee a safe operation and service life of the riser, it is necessary to carefully design its configuration and to analyze its performance.\u0000 In this study, taking the saddle-shaped riser as our model, the influences of main design parameters on the riser configuration, tension and stress are examined. These parameters include the installation position of buoyancy modules, the buoyancy ratio and motion of mining vehicle. Firstly, the analysis model of the riser response is established based on FEM in which the nonlinear large displacement and deformation of the structure are considered. Secondly, through our FEM simulation, the distribution and variation of tension and stress along the axial length of risers with different configurations are presented. Finally, the impacts of the mining vehicle motion on riser response are discussed. Our numerical results show that a small change of the buoyancy position and buoyancy ratio may lead to a significant change of the riser configuration, but a little change of riser tension/stress. And the saddle-shaped riser has a good tolerance performance to the bottom-end excitation.","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":"133214194","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}
K. Masuda, T. Ikoma, H. Eto, Y. Aida, Kazuki Murata
In this study, we consider and evaluate the applicability of the FEMA’s formula which is one of the main simple formulas for calculating impact forces through the comparison with our proposed numerical simulation model. We investigated the situation of collision with a thin structure such as a pillar by numerical experiments based on the particle method, in particular, we focus on the case where the drifting speed is fast in targeting the quay of Shimizu Port, Shizuoka prefecture. We compared the results of numerical experiments obtained by detailed simulations with FEMA’s formula and evaluated the applicable range of FEMA s formula for huge vessels. As results, it was suggested that the overestimation was occurred with FEMA’s formula for large vessel using the inundation height and its velocity. FEMA’s formula calculates the impact force of large vessel on the safe side if the drifting vessel speed is used: the condition of added mass coefficient changes the results, but these indicate the safe side in this study. On the other hand, the results of safety sides are fluctuated depending on the height of the action point of force. Therefore, we confirmed that there is a need to examine the height of the impact point when using FEMA’s formula for large vessels.
{"title":"Study on Applicability of FEMA Formula in Prediction of Impact Load by Tsunami Drifting Vessels on Coastal Zone Structures","authors":"K. Masuda, T. Ikoma, H. Eto, Y. Aida, Kazuki Murata","doi":"10.1115/omae2020-19088","DOIUrl":"https://doi.org/10.1115/omae2020-19088","url":null,"abstract":"\u0000 In this study, we consider and evaluate the applicability of the FEMA’s formula which is one of the main simple formulas for calculating impact forces through the comparison with our proposed numerical simulation model. We investigated the situation of collision with a thin structure such as a pillar by numerical experiments based on the particle method, in particular, we focus on the case where the drifting speed is fast in targeting the quay of Shimizu Port, Shizuoka prefecture.\u0000 We compared the results of numerical experiments obtained by detailed simulations with FEMA’s formula and evaluated the applicable range of FEMA s formula for huge vessels.\u0000 As results, it was suggested that the overestimation was occurred with FEMA’s formula for large vessel using the inundation height and its velocity. FEMA’s formula calculates the impact force of large vessel on the safe side if the drifting vessel speed is used: the condition of added mass coefficient changes the results, but these indicate the safe side in this study. On the other hand, the results of safety sides are fluctuated depending on the height of the action point of force. Therefore, we confirmed that there is a need to examine the height of the impact point when using FEMA’s formula for large vessels.","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":"126682417","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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