研究者データベース

宇都 正太郎(ウト シヨウタロウ)
北極域研究センター
教授

基本情報

所属

  • 北極域研究センター

職名

  • 教授

学位

  • 工学博士(1995年01月 大阪大学)

J-Global ID

研究分野

  • フロンティア(航空・船舶) / 船舶海洋工学 / 極域工学

職歴

  • 2021年07月 - 現在 北海道大学 北極域研究センター 教授
  • 2020年04月 - 2021年06月 一般財団法人日本船舶技術研究協会 審議役
  • 2016年04月 - 2020年03月 国立研究開発法人 海上・港湾・航空技術研究所 海上技術安全研究所
  • 2001年04月 - 2016年03月 独立行政法人 海上技術安全研究所
  • 2001年07月 - 2002年07月 国土交通省 海事局
  • 2000年11月 - 2001年03月 第42次日本南極地域観測隊
  • 1985年04月 - 2001年03月 運輸省船舶技術研究所
  • 1999年11月 - 2000年04月 ヘルシンキ工科大学 客員研究員
  • 1987年11月 - 1988年03月 第29次日本南極地域観測隊

学歴

  •         - 1985年03月   大阪大学   大学院工学系研究科   造船学専攻
  •         - 1983年03月   大阪大学   工学部   造船学科

所属学協会

  • 日本工学アカデミー   日本船舶海洋工学会   日本雪氷学会   

研究活動情報

論文

  • アイスチャートを用いた船舶の氷中抵抗推定精度の検証
    Uto Shotaro, Takenobu Toyota
    オホーツク海と極域海洋に関する第36回国際シンポジウム 124 - 127 2022年02月 [査読無し][通常論文]
  • 船舶の氷中抵抗推定におけるIce chartの適用
    宇都正太郎
    第37回寒地技術シンポジウム講演論文集 2021年10月 [査読無し][通常論文]
  • Kenta Hasegawa, Shotaro Uto, Haruhito Shimoda, Daisuke Wako, Takatoshi Matsuzawa
    Proceedings of the International Conference on Port and Ocean Engineering under Arctic Conditions, POAC 2019-June 2019年01月01日 [査読有り][通常論文]
     
    © 2019, Lulea University of Technology. All rights reserved. To estimate global ice loads exerted on a structure due to interaction with managed ice floes, we have been developing a numerical simulation method by a non-smooth discrete element method. In this study, a breakable ice element consisting of small square rigid body with a fixed joint function of the physics engine is introduced to our numerical simulation method in order to represent ice failure. To clarify the effect of the ice failure, we compared simulation results with experimental results obtained from ice tank tests conducted in National Maritime Research Institute. The results show that the breakable ice elements reasonably reduce peak loads to the experimental results in the condition where peak loads became extremely high in the simulation not considering ice failure. Furthermore, it is found that the state of ice failure is different depending on a coefficient of friction between ice floes. The state of ice failure similar to the experiment was sometimes observed for a larger coefficient of friction between ice floes.
  • Kenta Hasegawa, Shotaro Uto, Haruhito Shimoda, Daisuke Wako, Takatoshi Matsuzawa
    Proceedings of the International Offshore and Polar Engineering Conference 2018-June 1672 - 1678 2018年06月01日 [査読有り][通常論文]
     
    Copyright © 2018 by the International Society of Offshore and Polar Engineers (ISOPE) We are developing a numerical simulation method to evaluate global load exerted to an offshore structure in a managed ice condition. Non-smooth DEM is capable of efficiently calculating a large number of rigid body interactions according to the law of physics. An open source physics engine was used for the collision problem of a fixed conical structure - small ice floe interactions. A model experiment was conducted at the ice model basin of National Maritime Research Institute in order to obtain verification data. Through comparison between the numerical simulation results and the model test results, it was shown that the tendency of ice load and behavior of ice floes can be qualitatively reproduced well in case that global ice failure such as bending and splitting does not occur. It was clearly found that a peak ice load is associated with the formation of an ice load network from the structure to the edge of ice channel via ice floes. Based on this model, we can expect implementation of ice failure effect in non-smooth DEM simulation in the future.
  • Sadaoki Matsui, Shotaro Uto, Yasuhira Yamada, Shinpei Watanabe
    International Journal of Naval Architecture and Ocean Engineering 10 3 367 - 375 2018年05月01日 [査読有り][通常論文]
     
    The present paper considers the contact between energy-saving device of ice-class vessel and ice block. The main objective of this study is to clarify the tendency of the ice impact force and the structural response as well as interaction effects of them. The contact analysis is performed by using LS-DYNA finite element code. The main collision scenario is based on Finnish-Swedish ice class rules and a stern duct model is used as an energy-saving device. For the contact force, two modelling approaches are adopted. One is dynamic indentation model of ice block based on the pressure-area curve. The other is numerical material modelling by LS-DYNA. The authors investigated the sensitivity of the structural response against the ice contact pressure, the interaction effect between structure and ice block, and the influence of eccentric collision. The results of these simulations are presented and discussed with respect to structural safety.
  • Takatoshi Matsuzawa, Haruhito Shimoda, Daisuke Wako, Shotaro Uto, Qing He, Shinpei Watanabe
    Proceedings of the International Conference on Port and Ocean Engineering under Arctic Conditions, POAC 2017年06月01日 [査読有り][通常論文]
     
    A series of ice tank tests of a bulk carrier was conducted at National Maritime Research Institute. According to the Finnish-Swedish Ice Class Rules, lm thick brash ice channel was assumed as actual condition for ice class IA vessel and simulated in the ice tank. For the propulsion tests, two kinds of load-varying methods i.e. in brash ice and in open water, were employed. The difference in thrust at self propulsion point between these two methods was 8.1% at most, while RMSE of measurement in brash ice was 15.1%. The power required for 5knots in brash ice were estimated and compared with the rule-based calculation.
  • Sadaoki Matsui, Shotaro Uto, Yasuhira Yamada, Shinpei Watanabe
    Proceedings of the International Conference on Port and Ocean Engineering under Arctic Conditions, POAC 2017年06月01日 [査読有り][通常論文]
     
    The present paper considers the contact between energy-saving device of ice-class vessel and ice block and clarifies the ice impact force and the structural response from various points of view. The contact analysis is performed by using LS-DYNA finite element code. The main collision scenario is based on Finnish-Swedish ice class rules and a stern duct model is used as an energy-saving device. For the contact force, two modelling approaches are adopted. One is dynamic indentation model of ice block based on the pressure-Area curve. The other is numerical material modelling by LS-DYNA. The authors investigated the sensitivity of the structural response against the ice contact pressure, the interaction effect between structure and ice block, and the influence of eccentric collision. Furthermore, the simplified mechanical model was proposed to evaluate the structural response. The results of these simulations are presented and discussed with respect to structural safety.
  • Takatoshi Matsuzawa, Kenta Hasegawa, Shotaro Uto, Koh Izumiyama, Kazutaka Tateyama, Kazuki Nakamura, Chang Kyu Rheem, Akira Asada, Joji Yamamoto, Takayuki Asanuma
    Proceedings of the International Conference on Port and Ocean Engineering under Arctic Conditions, POAC 2017年06月01日 [査読有り][通常論文]
     
    Arctic is one of the most important areas for the future oil and gas development. However presence of ice is a serious hazard for safe, efficient and sustainable developments. The authors developed accurate ice observation technologies and verified their functions by field campaigns in Japan and Greenland. The "EM-BIRD" (airborne Electro-Magnetic induction sensor of ice thickness) was improved by installing a portable microwave radiometer (PMR) and a laser scanner for observing more comprehensive information including snow depth and surface geometry of ice. The authors developed the on-board pulse-doppler ice radar and the parametric sub-bottom profiler which are capable of measuring motions and distributions of sea ice, and gouging depth by massive ice features with high accuracy. The authors also developed ice database system containing satellite remote-sensing and field data measured by the developed sensors for the operability analysis of arctic facilities.
  • Fuko Sugimoto, Takeshi Tamura, Haruhito Shimoda, Shotaro Uto, Daisuke Simizu, Kazutaka Tateyama, Seita Hoshino, Toshihiro Ozeki, Yasushi Fukamachi, Shuki Ushio, Kay I. Ohshima
    POLAR SCIENCE 10 1 43 - 51 2016年03月 [査読有り][通常論文]
     
    Under the Japanese Antarctic Research Expedition (JARE) program, sea-ice thickness has been routinely monitored off Lutzow-Holm Bay (East Antarctica) during the summer (mid-December to early January) since 2000/01, using an electromagnetic induction (EM) instrument onboard the icebreaker Shirase. Analysis of these data over a 10-year period, combined with visual observations using a simplified form of the ASPeCt (Antarctic Sea ice Processes and Climate) protocol, suggests a strong interannual variability in sea-ice thickness in this region. For the repeat pack-ice observation area, where the sea-ice thickness averaged over the nine seasons is similar to 1.9 m, mean thicknesses of observed sea-ice in 2010/11 and 2011/12 are exceptionally large, at similar to 3.3 and similar to 5.8 m, respectively. This result is strongly related to regional patterns of sea ice dynamics. Ice convergence caused by anomalous northerly winds was particularly high in 2011/12, suggesting that the extremely thick ice observed in that season resulted largely from sea-ice deformation processes (including pressure ridging). Longer-term analysis of data from the past 34 years confirms that sea-ice conditions and thickness off Lutzow-Holm Bay in summer are determined mainly by the large-scale pattern of atmospheric pressure in December. (C) 2015 Elsevier B.V. and NIPR. All rights reserved.
  • Shotaro Uto, Takatoshi Matsuzawa, Haruhito Shimoda, Daisuke Wako, Akihisa Konno, Takayuki Asanuma, Kazuhisa Otsubo
    Proceedings of the International Conference on Port and Ocean Engineering under Arctic Conditions, POAC 2015-January 2015年01月01日 [査読有り][通常論文]
     
    In order to find the feasibility of the Arctic drilling and developments using floating offshore structures, we conducted the research on ice loads in managed ice condition exerted on the ship-shaped floater by experiment and numerical simulation. The experiment was conducted at the ice model basin of the National Maritime Research Institute, Japan. Through the comparison with experiment results, it was found that the numerical simulation was capable of predicting ice load qualitatively well. It showed good agreement for the surge force and predicted the same order of sway force. Finally, a simple prediction formula was established for the average surge and sway force, and yaw moment. Its accuracy was validated by the experimental data.
  • Takatoshi Matsuzawa, Naoto Sogihara, Masaru Tsujimoto, Shotaro Uto
    Proceedings of the International Conference on Port and Ocean Engineering under Arctic Conditions, POAC 2015-January 2015年01月01日 [査読有り][通常論文]
     
    The positive usage of the Northern Sea Route (NSR) is arising as a result of arctic ice melting in recent years. National Maritime Research Institute has developed an advanced vessel performance simulator in ice for accurate estimation of ship performance such as propulsion power, speed reduction and fuel consumption, taking the main engine characteristics into consideration. The vessel performance simulator, "VESTA" has not originally developed in ice but in wave and wind. The authors incorporated two ice resistance models, Kashitelijan-Poznjok-Ryblin's (KPR) for small ice floes and Lindqvist's for large ice floes, in VESTA for performance calculation in ice. The summer transit of ice-strengthened merchant vessel must be along marginal ice zone with pack ice rather than level ice. Thus we selected the KPR model, which requires ice concentration, thickness and floe size as input parameters of ice. Ice concentration of September from satellite observations was given to the simulator. Ice thickness and floe size were derived from the past onboard observation in the summer voyage along NSR. The shiptype virtually employed was a bulk carrier of 73,000 DWT with 9MW of M/E output. Ship performance was estimated by VESTA along the seaway from Tokyo to Rotterdam via NSR. Several routing scenarios were simulated in order to investigate sensitivities of ice conditions for ship performance. Each route was selected so as to avoid severe ice with ice concentration. The mean ice concentration in the route was ranged from 8% to 33%. The calculation resulted in taking 3 weeks to transit from Tokyo to Rotterdam. The ship speed was up to 14 knots in open water and reduced to about 4 knots in ice. As a conclusion, the simulations showed that the NSR holds potential to reduce shipping cost of 35% as compared with Suez Canal route.
  • Shotaro Uto, Haruhito Shimoda, Daisuke Wako, Takatoshi Matsuzawa
    Proceedings of the International Conference on Port and Ocean Engineering under Arctic Conditions, POAC 2015-January 2015年01月01日 [査読有り][通常論文]
     
    Ships encounter various ice conditions such as level ice, ridged ice, floe ice and ice-clogged channel. Various models have been developed so far for the prediction of ice resistance in various ice conditions. The authors proposed the hybrid model of resistance prediction of ships navigating in floe ice including small ice floes, ice-clogged channel and a large ice floe. This model consists of two existing models, i.e. Kashitelijan-Poznjok-Ryblin and Lindqvist model. The former model gives the ice load at the limit momentum condition and can be fundamentally applied to the resistance prediction of ships in small ice floes. The latter model is originally developed for resistance prediction in level ice. It gives the ice load at the limit stress condition and can be applied to the prediction in a large ice floe. Resistance in floe ice can be determined as the smaller resistance predicted by either of two models. The former model is also applicable to the resistance prediction in ice-clogged channel by taking the influence of the restricted ice area into account. The accuracy of each model was validated through comparisons with the model-scale experiments conducted at the ice model basin of the National Maritime Research Institute. Validation study was also conducted through comparisons with the full-scale thrust measurements in the southern part of the Sea of Okhotsk, Japan. It is found that the proposed model is capable of predicting the resistance in floe ice of various sizes and concentrations with reasonable accuracy. This model is applicable to the transit simulation along the Northern Sea Route.
  • Viscous CFD analysis of stern duct installed on Panamax bulk carrier in model and full scale
    Nobuaki Sakamoto, Yasutaka Kawanami, Munehiko Hinatsu, Shotaro Uto
    Proc. 13th International Conference on Computer and IT Application in the Maritime Industries 72 - 82 2014年05月 [査読有り][通常論文]
  • Nobuaki Sakamoto, Yasutaka Kawanami, Shotaro Uto, Noriyuki Sasaki
    JOURNAL OF SHIP RESEARCH 57 1 24 - 41 2013年03月 [査読有り][通常論文]
     
    Reynolds-averaged Navier-Stokes simulations together with verification and validation studies for a low L/B twin-skeg container ship are carried out using SURF version 6.44, which is a high-fidelity RANS solver for ship hydrodynamics developed at the National Maritime Research Institute: single-phase level set free surface, Spalart-Allmaras/k-omega turbulence, and body-force propeller models; finite volume discretization; and parallelized by openMP (R) for high-performance computing. At the beginning, simulation numerical uncertainty has been quantified for resistance and self-propulsion coefficients on the basis of the standard V&V procedure recommended by the International Towing Tank Conference. Then the resistance and self-propulsion simulations are carried out at several speeds ranging from low to medium Froude numbers. The overall results are encouraging in that the solver accurately predicts resistance and self-propulsion coefficients as well as velocity distribution at the propeller plane in comparison to the available experimental data. Further sophistications in computational method, especially in estimating self-propulsion coefficients, will lead the solver to be more practical and powerful design tool.
  • Investigations of design criteria for ships with split-stern by RANS
    Nobuaki Sakamoto, Yasutaka Kawanami, Shotaro Uto
    Proc. 15th Numerical Towing Tank Symposium 2012年10月 [査読有り][通常論文]
  • Joji Yamamoto, Hideyuki Oka, Yasuharu Nakajima, Shotaro Uto, Sotaro Masamobu
    Proceedings of the International Offshore and Polar Engineering Conference 117 - 121 2012年09月17日 [査読有り][通常論文]
     
    The exclusive economic zone (EEZ) of Japan has a very wide area. Accordingly, technology for the effective exploitation and use of mineral resources in the EEZ will be a key for sustainable development in Japanese industry. When marine mineral resources are developed, it is necessary to evaluate an environmental impact on the sea area and the deep seafloor. Then, a clarification is required for an environmental impact of the particles on the sea area and the deep seafloor by mining and discharged from the platform into the ocean. We have developed an analytical tool for evaluating environmental impact of the seafloor resource development. Copyright © 2012 by the International Society of Offshore and Polar Engineers (ISOPE).
  • Marcio Yamamoto, Shotaro Uto, Tomo Fujiwara, Motohiko Murai
    PROCEEDINGS OF THE ASME 31ST INTERNATIONAL CONFERENCE ON OCEAN, OFFSHORE AND ARTIC ENGINEERING, VOL 3 3 47 - 55 2012年 [査読有り][通常論文]
     
    In the past of the offshore petroleum production, each riser had conveyed the hydrocarbon production from a single vertical well; the riser's internal flow rate was relatively low and only the internal fluid pressure was taking into account for the riser analysis. Other internal flow effects, such as internal fluid's linear moment, and Coriollis effects, were neglected. However, the paradigm for petroleum production in ultra-deepwater is shifting nowadays. New technologies, such as horizontal wells, have increased the production rate from a single well. In addition, a subsea booster system can increase both pressure and flow rate of the riser's conveyed fluid. Further, the Offshore Mining is rising as a new industry and will demand riser systems to convey, at high flow rates, the mineral ore's slurry from the seafloor up to the production support vessel. In a previous experiment, the effects of the internal flow on a vertical riser were investigated. In the current experiment, the main objective is to investigate the effect of the internal flow on the dynamic response of a pipe in "jumper configuration". The experiment was carried out at the Deep Sea Basin of the National Maritime Research Institute using a 10 m long flexible pipe. The actual "jumper" is a piece of flexible riser, in U-shaped configuration, that connects the main structure of "Self-Standing Hybrid Riser" to the production vessel. During the experiment, fresh water was pumped into the model by positive displacement pump; and an oscillator applies a harmonic vibration on one pipe's end. Then the pipe's dynamic response is measured by the Deep Sea Basin's 3D Visual Measurement System. Results for different internal flows and oscillations are compared.
  • Investigations for wake field of single-screw and twin-skeg container ships in model and full-scale by unstructured grid based RANS solver
    Nobuaki Sakamoto, Yasutaka Kawanami, Shotaro Uto
    Proc. 14th Numerical Towing Tank Symposium 2011年10月 [査読有り][通常論文]
  • N. Hayashi, T. Matsubara, S. Uto
    Proceedings of the International Offshore and Polar Engineering Conference 1305 - 1312 2011年09月19日 [査読有り][通常論文]
     
    In this study the authors execute free-hanging flexible riser model tests in a tank and analysis to clear up fundamental dynamic effects of vibration applied in different directions to the top end of the riser on the tension at the top end. Through tests and analytical results we obtained the axial tension at the top end of a riser resulting from vertical vibration which constitutes a fundamental issue requiring attention to its basic design. And vortex induced vibration may also occur in oscillating flow resulting from the motion of vessels due to waves. Attention must be paid to this when estimating the service life of a riser. Copyright © 2011 by the International Society of Offshore and Polar Engineers (ISOPE).
  • Motohiko Murai, Marcio Yamamoto, Shotaro Uto, Tomo Fujiwara
    OMAE2011: PROCEEDINGS OF THE ASME 30TH INTERNATIONAL CONFERENCE ON OCEAN, OFFSHORE AND ARCTIC ENGINEERING, VOL 4 4 495 - + 2011年 [査読有り][通常論文]
     
    Nowadays, flexible risers are widely deployed in various configurations for the production of hydrocarbons in offshore fields. For example, in the self-standing hybrid risers' applications, a single riser or a set of risers are suspended by a subsurface buoy called "Can". Then a piece of flexible riser connects the Can to the production platform conveying the hydrocarbon production stream. This work concerns about this jumper an experiment using a 10 m long model was carried out at the Deep Sea Basin of the National Maritime Research Institute in Japan. The model was made by three concentric unbonded layers: a silicon made inner layer; a crisscross steel wire layer; and a rubber made outer layer During this experiment, the model was suspended through both ends; one model's end was fixed and the other end was connected to an oscillator that generates the oscillatory motion in three different directions. In addition, a positive displacement pump injected fresh water into the model. Further the model was instrumented with two degrees of freedom accelerometers fixed along its length; and a six degrees of freedom force/torque transducer was also installed at one pipe end. In addition, the Deep Sea Basin's Visual Measurement System tracks and calculates the motion of several measurement stations along the pipe. A parametric analysis was carried out changing the oscillating frequency and internal flow rate. Discussion and results of numerical simulation are also included.
  • Joji Yamamoto, Hideyuki Oka, Yasuharu Nakajima, Shotaro Uto, Shunji Inoue, Shigesuke Ishida
    OMAE2011: PROCEEDINGS OF THE ASME 30TH INTERNATIONAL CONFERENCE ON OCEAN, OFFSHORE AND ARCTIC ENGINEERING, VOL 5 5 185 - 191 2011年 [査読有り][通常論文]
     
    The exclusive economic zone (EEZ) of Japan has a very wide area due to a lot of islands in Japanese Archipelago. As the worldwide supply and demand of natural resources and foods are being tight, the technology for the effective use of the EEZ will become the key for the sustainable development of Japan. From this background, the Ministry of Land, Infrastructure, Transport and Tourism of Japan (MLIT) started an R&D project of floating offshore platform technologies in 2007[1]. In this project an integrated design support tool is developed for evaluating the economical and safety aspects of the offshore platforms. This tool contains the function to estimate an environmental impact of seafloor resource development. We postulated the process of seafloor resource development as follows. The ores mined on seabed are sent up to the platforms as a mixture of the ore particles and water, then the waste water containing inorganic suspended particles is discharged into sea. The particles exhausted in the sea are transported by the advection and diffusion, and sink gradually on seafloor. We developed an analytical code simulating the distribution of discharged particle in both sea and sediments by a simple technique. Mass Consistent Flow Model is used to save the time in the calculation of ocean flow. In addition, the ecosystem model in sediment is developed to estimate the ecological impact of seafloor resource development. It includes benthic organism, zooplankton, bacteria, and particulate organic matter as the components. The ecological impact was assessed based on the recovery period of the biomass. In this paper, the outline of this environmental impact analysis tool and results of the trial calculation for seafloor resource mining are shown.
  • Yasuharu Nakajima, Shotaro Uto, Shigeo Kanada, Joji Yamamoto, Ichihiko Takahashi, Sho Otabe, Jun Sadaki, Katsunori Okaya, Seiji Matsuo, Toyohisa Fujita
    OMAE2011: PROCEEDINGS OF THE ASME 30TH INTERNATIONAL CONFERENCE ON OCEAN, OFFSHORE AND ARCTIC ENGINEERING, VOL 5 5 157 - + 2011年 [査読有り][通常論文]
     
    Seafloor Massive Sulfides (SMS), which were formed by deposition of precipitates from hydrothermal fluids vented from seafloor, is one of unconventional mineral resources beneath deep seafloors in the world. The authors have proposed the concept of seafloor mineral processing for development of SMS, where useful minerals included in SMS ores are separated on seafloor to be lifted while the remaining gangue is disposed on seafloor in appropriate ways. To apply column flotation, one of conventional methods in mineral processing, to seafloor mineral processing, the authors carried out simulating experiments of column flotation on deep seafloor using ores including copper, iron, lead and zinc as metallic elements. Prior to the experiments at high pressures, preparatory experiments at the atmospheric pressure were carried out to find out the optimum condition of the properties of pulp, a mixture of feed ore, water and chemical reagents. In flotation experiments at high pressures, formation and overflow of froth layer by bubbling were observed at 1MPa in both of pulps with pure water and artificial seawater. The analytical data showed that the concentration of metallic elements such as copper and zinc in the concentrates recovered from the experiments was higher than that in the feed ores while the concentration of silicon and calcium, which are assigned to gangue, in the concentrates was lower than that in the feed ores. These results suggest that column flotation can be applied to operation on seafloor.
  • Tomo Fujiwara, Shotaro Uto, Shigeo Kanada
    OMAE2011: PROCEEDINGS OF THE ASME 30TH INTERNATIONAL CONFERENCE ON OCEAN, OFFSHORE AND ARCTIC ENGINEERING, VOL 7 7 487 - 492 2011年 [査読有り][通常論文]
     
    In recent years, a number of deepwater development projects are running worldwide. As the water depth increases, safety and reliability of the riser is a critical issue. One of the most important matters is vortex-induced vibration (VIV). In the deepwater area with strong current, for example in the Gulf of Mexico, a riser pipe's VIV motion changes continually due to the change of hydrodynamic conditions. In order to assess safety and reliability of deepwater riser, investigation of the dynamic variation of riser VIV is important. This paper deals with top tensioned riser: To clarify the phenomena of dynamic variation of the riser's vibration mode, a large-scale experiment using a 28.5 m long model was carried out at the Deep Sea Basin of the National Maritime Research Institute in Japan. In this experiment, the model's bottom end was fixed, while top end was connected to a tensioner. The current generating system was installed to make flow from water surface to about 5m in depth. A measurement of riser VIV motion in current condition was carried out by changing the model's top tension from self-weight balanced condition to four times of the self-weight. Vibration mode widely changed from high mode of up to 15th to low mode of 5th. In order to investigate an influence of the change of vibration mode on the riser VIV motion, a series of experiments were conducted with the periodic variation of top tension. It was found that the traveling wave occurred from top to bottom end in a moment of vibration mode changed
  • Yasuhiro Namba, Shotaro Uto, Tadashi Nimura, Kentaroh Kokubun, Takako Kuroda, Tsuyoshi Miyazaki, Yasuyuki Okumura, Masahiko Ozaki
    International Journal of Offshore and Polar Engineering 20 1 7 - 14 2010年03月 [査読有り][通常論文]
     
    Using various cylindrical rigid riser models, top forced oscillation tests have been carried out to study interactions between hung-off risers and an internal fluid. A theoretical model of a weakly-damped oscillator has been applied to reveal the mechanism of such interactions. It has been shown that the theoretical model can explain the experimental results adequately. Coefficients of friction on inner surfaces of risers have been quantitatively investigated. Applying the theory for oscillating flows in pipes, the expressions that represent relationships between friction coefficients and Reynolds numbers have been partly confirmed with the experimental data. Copyright © by The International Society of Offshore and Polar Engineers.
  • Marcio Yamamoto, Motohiko Murai, Shotaro Uto, Tomo Fujiwara, Shigeo Kanada, Luis A. R. Quadrante, Ken Haneda
    PROCEEDINGS OF THE ASME 29TH INTERNATIONAL CONFERENCE ON OCEAN, OFFSHORE AND ARCTIC ENGINEERING 2010, VOL 5, PTS A AND B 5 333 - 344 2010年 [査読有り][通常論文]
     
    The pipes are playing an important role in the offshore environment. Risers and pipelines are widely deployed by the petroleum industry for the well drilling and hydrocarbons production. Whereas during drilling, a mixture of drilling mud and solids in suspension (rock cuttings).flows through the drilling riser; during the production, mono or multiphase flow (comprising oil, water and gas) takes place within the production system. However up till now, most of investigations on offshore pipelines and risers have neglected the effects of the internal flow and have focused mainly on the interaction among pipe's structure, hydrodynamic forces and offshore platform's motion. This paper deals with the interaction between the pipe structure and its internal flow. An experimental analysis was carried out, in the Deep Sea Basin of the National Maritime Research Institute (Japan), using a model of 10 m length. In this experiment, a mono-phase fluid of liquid and another hi-phase fluid of liquid and solids in suspension are used as the internal flow fluid and a parametric analysis using the internal flow rate and pipe's oscillating frequency was carried out. Discussion about the experimental results is also included.
  • Sotaro Masanobu, Shunji Kato, Shigesuke Ishida, Shotaro Uto
    PROCEEDINGS OF THE ASME 29TH INTERNATIONAL CONFERENCE ON OCEAN, OFFSHORE AND ARCTIC ENGINEERING 2010, VOL 3 3 257 - 262 2010年 [査読有り][通常論文]
     
    National Maritime Research Institute of Japan (NMRI) has been developing the integrated design support tool, called "Harmonic Design Tool", for evaluating economical / safe / environmental aspects of the offshore platform. We are also conducting the conceptual design of the offshore platforms for assessing the availability and accuracy of this design support tool. Seafloor massive sulphides (SMS) are high-grade hydrothermal deposits rich in copper, zinc and lead with a high gold and silver content. The Japanese Economic Exclusive Zone (FEZ) is well known to have high potential of SMS. Thus we decided the SMS mining as one of the most promising applications for the offshore platform technologies. Based on the published potential map of resources and the metocean database established in this project, we decided Izu-Bonin Arc as the target sea area and derived the design and operation conditions for the offshore mining platform. Then we proceeded to the basic concept such as the production rate and storage capacity, dynamic positioning system for station keeping and operation availability. This paper presents the review of the conceptual design of the offshore platform for SMS mining.
  • Kazuki Nakamura, Hiroyuki Wakabayashi, Shotaro Uto, Shuki Ushio, Fumihiko Nishio
    IEEE GEOSCIENCE AND REMOTE SENSING LETTERS 6 2 277 - 281 2009年04月 [査読有り][通常論文]
     
    To investigate the suitability of synthetic aperture radar (SAR) polarization data to estimate the sea-ice thickness in early summer in Lutzow-Holm Bay, Antarctica, we compared in situ ice thicknesses with the corresponding backscattering coefficient for each polarization and the VV-to-HH backscattering ratio. The VV-to-HH backscattering ratio was derived from data acquired by ENVISAT Advanced SAR (ASAR). This ratio is related to the near-surface dielectric constant of the sea ice, which is, in turn, related to the developing process of ice and, thus, its thickness via changes in the near-surface sea-ice salinity. The sea ice encountered in the study area is close first-year pack ice and fast ice. For these old and relatively rough sea-ice types, the VV-to-HH backscattering ratio can be expected to depend on salinity-driven changes in the near-surface dielectric constant rather than changes of the surface roughness. We applied the empirical relationships between the ice thickness and the VV-to-HH backscattering ratio with the linear and logarithm fits to ASAR data. The linear fit gave the reliable result, with an rms error being 0.08 m and a correlation coefficient being 0.91, when compared to in situ fast-ice thickness.
  • T. Toyota, K. Nakamura, Shotaro Uto, K. I. Ohshima, N. Ebuch
    INTERNATIONAL JOURNAL OF REMOTE SENSING 30 12 3171 - 3189 2009年 [査読有り][通常論文]
     
    Although satellite data are known to be useful for obtaining ice thickness distribution for perennial sea ice or in stable thin sea ice areas, their use in the seasonal sea ice zone (SIZ) is still unresolved. In this study, we approached the problem of ice thickness retrieval by using L-band Synthetic Aperture Radar (SAR). In the SIZ, ice thickness growth is closely related to ridging activity and therefore we expected surface roughness to be correlated to ice thickness. L-band SAR is suitable for detecting such surface roughness and should be a useful tool for obtaining ice thickness distribution. To verify this correlation, we conducted shipborne electromagnetic (EM) inductive sounding and supersonic profiling observations with an icebreaker, coordinated with airborne L-band SAR observations in the southern Sea of Okhotsk in February 2005. The surface elevation was estimated by representing the ship's motion with a low-pass filter. Backscattering coefficients correlated well with ice thickness and surface roughness, defined by the standard deviation of the surface elevation. This result sheds light on the possibility of determining ice thickness distribution in the SIZ.
  • Marcio Yamamoto, Motohiko Murai, Katsuya Maeda, Shotaro Uto
    OMAE 2009, VOL 3 3 213 - 220 2009年 [査読有り][通常論文]
     
    Nowadays pipes arc widely deployed in the offshore environment especially in the petroleum industry where rigid and flexible pipes are used for well drilling and hydrocarbon production Whereas during drilling, a mixture of drilling mud, rock cuttings and sometimes gas flows through the drilling riser, during production mono or multiphase (comprising oil, water and gas) flow takes place within the system. However up till now, most of the studies on offshore pipelines and risers have been focused on the pipe structure and its interaction with hydrodynamic forces and offshore platforms. In particular for numerical computation studies and reduced scale model experiments, the pipe is usually modeled as a tensioned beam and sometimes only the internal pressure is taken into account with other effects due to its internal flow being neglected. This paper deals with the interaction between the pipe structure and its internal flow. In order to verify the internal flow effects, an experimental analysis was carried out not using, a reduced scale model. In particular, mono-phase fluid flows into the pipe and a parametric analysis using the flow rate was carried out. Discussion about the experimental results and numerical applications is also included.
  • Yasuhiro Namba, Shotaro Uto, Tadashi Nimura, Kentaroh Kokubun, Takako Kuroda, Tsuyoshi Miyazaki, Yasuyuki Okumura, Masahiko Ozaki
    Proceedings of the International Offshore and Polar Engineering Conference 365 - 372 2009年 [査読有り][通常論文]
     
    Using various cylindrical rigid riser models, top forced oscillation tests have been carried out to study interactions between hung-off risers and an internal fluid. A kind of theoretical model of a weakly-damped oscillator has been applied to reveal the mechanism of such interactions. It has been shown that the theoretical model can explain the experimental results adequately. Coefficients of friction on inner surfaces of risers have been quantitatively investigated. Applying the theory for oscillating flows in pipes, the expressions that represent relationships between friction coefficients and Reynolds numbers have been partly confirmed with the experimental data. Copyright © 2009 by The International Society of Offshore and Polar Engineers (ISOPE).
  • 宇都 正太郎, 前田 克弥
    Marine engineering : journal of the Japan Institution of Marine Engineering = マリンエンジニアリング : 日本マリンエンジニアリング学会誌 43 5 677 - 682 The Japan Institute of Marine Engineering 2008年09月01日 
    The Deep Sea Basin at the National Maritime Research Institute of Japan was constructed in 2002 because of the increasing demand for R&D on deep sea technology; such as the riser technology for deep water oil and gas production, drilling and deep water utilization. In this paper, we described the main characteristics of the Deep Sea Basin. It consists of two parts, the circular basin with a depth of 5m and with 14m in diameter. The deep pit is 30m in depth and 6m in diameter. It has the maximum depth of 35m. It is one of the deepest model basins in the world. 128 absorbing-type wave generators surround the circumference of the circular basin. For simulation of ocean currents we have one main current generator for the circular basin and six compact current generators for the deep pit. For measuring the dynamic behavior of underwater objects we have 3-D measurement equipment. This consists of 20 sets of two high resolution CCD cameras and one underwater light. Finally, we described the results of model tests on the behaviour of the riser pipe, of the Ocean Nutrient Enhancer"TAKUMI."This is one example of the utilization of the Deep Sea Basin.
  • Yasuharu NAKAJIMA, Hideyuki SHIROTA, Katsuya MAEDA, Kunihiro HOSHINO, Shotaro UTO, Kenkichi TAMURA
    The proceedings of the JSME annual meeting 2008.3 0 161 - 162 2008年
  • 鈴木英之, 木村 亮太, 宇都 正太郎, 林 昌奎, 國分 健太郎, 有馬 安則
    日本船舶海洋工学会論文集 8 259 - 266 日本船舶海洋工学会 2008年 [査読有り][通常論文]
     
    A time domain analysis method of Vortex Induced Vibration (VIV) was developed for risers and towing pipes with curvature. Risers are increasingly installed in deepwater and catenary shape is used utilizing increasing relative flexibility. For example, riser designs such as Steel Catebary Riser (SCR), Compliant Vertical Access Riser (CVAR), Lazy Wave Steel Catenary Riser, etc. are investigated and put to practical use. Other application areas of deepwater pipe structures are CO2 dilution into ocean concerning global warming. Long towed pipe is used in the moving ship concept. Long pipe structure is also used in deepwater mining. VIV is expected for the inclined pipes. Quantitative analysis of VIV behavior is becoming increasingly important to estimate the fatigue damage of the structures. A time domain VIV simulation method was developed. The analysis method is basically a nonlinear FEM (Finite Element Method) of underwater line structure. The VIV hydrodynamic force is calculated at each time step consulting database of VIV hydrodynamic force. VIV hydrodynamic force on a real scale pipe section subjected to harmonic oscillation was measure at high Reynolds number and arranged into a database. A numerical filter which evaluates amplitude, frequency and phase of local response of a riser from the time history of pipe vibration was developed. Using this filter, response parameters of local vibration is evaluated, and consulting the database and amplitude and phase of VIV force is estimated. The evaluated instantaneous VIV force is applied to the riser. From the procedure the time domain response of pipe is calculated. The validity of the method was verified by comparison with small scale and large scale experimental results carried out in the towing tank. The accuracy of the method is discussed.
  • Quasisteady theory for the hydrodynamic forces on a circular cylinder undergoing vortex-induced vibration
    西佳樹, 國分健太郎, 星野邦弘, 宇都正太郎
    Journal of Marine Science and Technology 2008年 [査読有り][通常論文]
  • Elton J. B. Ribeiro, Gilberto Bruno Ellwanger, Marcos de Siqueira Queija, Shotaro Uto
    PROCEEDINGS OF THE 27TH INTERNATIONAL CONFERENCE ON OFFSHORE MECHANICS AND ARCTIC ENGINEERING - 2008, VOL 3 3 369 - 376 2008年 [査読有り][通常論文]
     
    When the oil exploration and exploitation moved away from the shore to deeper ocean, the riser interference became an important issue to be addressed during platform design. It became so important, particularly, when a great numbers of rigid risers are installed on the platform. Those kinds of risers are particularly used at Spar buoy and TLP platform. A conservative approach for riser interference design can result on the oversize platform or to reduce the number of wells hanging on it. On the other hand, a non conservative approach can bring serious problems, like collision of risers, which can cause a dent on the riser wall and it may reduce its fatigue life. In order to identify the hydrodynamic behavior of one riser placed in the vicinity of other one, Petrobras R&D Center carried out some experimental and numerical studies for getting their hydrodynamic behavior when they are aligned and spaced by 2, 3, and 5 times diameter.
  • Koh Izumiyama, Tadanori Takimoto, Shotaro Uto
    10th International Symposium on Practical Design of Ships and other Floating Structures, PRADS 2007 2 1287 - 1294 2007年12月01日 [査読有り][通常論文]
     
    A series of ship model tests in level ice were performed at National Maritime Research Institute with a local ice load measurement by way of a tactile sensor system. It was observed that the ice load distribution in the bow region was of a broken-line-like fashion in which short load patches were aligned in a horizontal line. Field test results were analyzed to see if this could also be observed in the full-scale conditions. The analysis of the data measured on board PM Teshio of Japan Coast Guard showed that the ice load in the bow is also broken-line-like. More importantly, the data showed that the higher loads act on shorter load patches. The data from the US Coast Guard Cutter Polar Star also suggested that the higher load is the more concentrated. Discussions were conducted on the interpretation of these results from a viewpoint of the ice load model on ship hulls. © 2007 American Bureau of Shipping.
  • 國分健太郎, 星野邦弘, 西佳樹, 宇都正太郎
    日本船舶海洋工学会講演会論文集 5 5E 95 - 96 公益社団法人日本船舶海洋工学会 2007年11月 [査読無し][通常論文]
  • 大水深ライザーシステムの安全性に関する研究
    田村兼吉, 宇都正太郎, 安藤裕友, 國分健太郎, 前田克弥, 伊藤和彰, 新冨恭子, 高橋一比古, 丹羽敏男, 田中義久, 牛嶋通雄, 吉成仁志, 千秋貞仁, 渡辺喜保, 金裕哲, 崎野良比呂
    海技研報告 7 3 69 - 131 2007年 [査読無し][通常論文]
  • Takenobu Toyota, Kay I. Ohshima, Naoto Ebuchi, Kazuki Nakamura, Shotaro Uto
    IGARSS: 2007 IEEE INTERNATIONAL GEOSCIENCE AND REMOTE SENSING SYMPOSIUM, VOLS 1-12 3997 - + 2007年 [査読有り][通常論文]
     
    Airborne Polarimetric and Interferometric Synthetic Aperture Radar (Pi-SAR) observation, conducted in the southern Sea of Okhotsk in February 2005, provided the opportunity to validate the retrieval of ice thickness distribution. In conjunction with the airborne SAR observation, in-situ ice thickness and ice-surface roughness measurements were carried out in the same area with ship-borne electromagnetic (EM) inductive sounding and supersonic profiling, respectively. Based on the analyzed results of data acquired in this experiment, this paper examine the possibility of ice thickness retrieval from the L-band SAR backscattering data in the seasonal ice zone (SIZ).
  • Katsuya Maeda, Ichihiko Takahashi, Kazuaki Itoh, Kentaroh Kokubun, Kazuyuki Ohuchi, Satoshi Masuda, Shotaro Uto
    Proceedings of the 26th International Conference on Offshore Mechanics and Arctic Engineering, Vol 1 1 749 - 755 2007年 [査読有り][通常論文]
     
    For pumping up deep ocean water, a SPAR type floating structure with a steel riser pipe was installed in Sagami Bay, Japan, in 2003. The riser pipe, which is 175 m long and 1.0 m in diameter, was connected to the floating structure by two mooring chains. At the middle height of the riser pipe, strain gages were attached on the pipe surface so that they faced to 8 directions at equal angles. The authors measured not only strains but also motions of the floating structure and wave and current conditions from 2003 to 2005. From these measured results in actual sea, it was found that the strains (or stresses) of the riser pipe are mostly concerned with motions of the floating structures, more than wave and current conditions. In order to make clear this phenomenon, the authors carried out forced oscillation tests by using a reduced riser pipe model in the Deep-sea Basin in National Maritime Research Institute, along with some numerical simulations based on FEM. In this paper, we show the results of the model tests and numerical simulations compared with the measured results in actual sea.
  • Tateyama K., Shirasawa K., Uto S., Kawamura T., Toyota T., Enomoto H.
    Annals of Glaciology 44 1 240 - 246 International Glaciological Society 2006年11月 
    Electromagnetic.induction (EM) instruments can be used to estimate sea-ice thickness because of the large contrast in the conductivities of sea ice and sea water, and are currently used in investigations of sea-ice thickness. In this study we analyze several snow, ice and sea-water samples and attempt to derive an appropriate formula to transform the apparent conductivity obtained from EM measurements to the total thickness of snow and ice for all regions and seasons. This was done to simplify the EM tuning procedure. Surface EM measurement transects with the instrument at varying heights above the ice were made in the Chukchi Sea, off East Antarctica, in the Sea of Okhotsk and in Saroma-ko (lagoon). A standardized transformation formula based on a one-dimensional multi-layer model was developed that also considers the effects of water-filled gaps between deformed ice, a saline snow slush layer, and the increase in the footprint size caused by increasing the instrument height. The overall average error in ice thickness determined with the standardized transform was <7%, and the regional average errors were 2.2% for the Arctic, 7.0% for the Antarctic, 6.5% for the Sea of Okhotsk and 4.4% for Saroma-ko.
  • Kunio Shirasawa, Kazutaka Tateyama, Toru Takatsuka, Toshiyuki Kawamura, Shotaro Uto
    Polar Meteorology and Glaciology 20 53 - 61 国立極地研究所 2006年11月01日 [査読有り][通常論文]
     
    Measurements of ice thickness were carried out by a ship-borne electromagnetic induction instrument mounted on the R/V Xuelong during the Second Chinese National Arctic Research Expedition (CHINARE-2003) in summer 2003 in the Chukchi Sea. A 1-D multi-layer model, consisting of three layers of snow, ice and seawater, was used to calculate the total thickness of snow and sea ice. The time series of total thickness from 24 August to 7 September 2003 indicates that deformed and second-/ multi-year ice floes appear frequently in very close pack ice farther from the ice edge, while thinner ice floes less than 1 m are frequently found in open pack ice. The probability density function of total thickness shows that a major peak appears at around 1.5 m thickness in very close pack ice, presumably corresponding to second-year or deformed ice. Also shown is a peak at around 0.3 m thickness, corresponding to typical level ice in open pack ice. © 2006 National Institute of Polar Research.
  • 戸城 亮, 榎本 浩之, 舘山 一孝, 豊田 威信, 宇都 正太郎
    日本雪氷学会全国大会講演予稿集 2006 35 - 35 公益社団法人 日本雪氷学会 2006年
  • Standardization of electromagnetic induction measurements of sea ice thickness in polar and sub–polar seas
    K. Tateyama, K. Shirasawa, S. Uto, T, Kawamura, T. Toyota, H. Enomoto
    Annals of Glaciology 44 261 - 268 2006年 [査読有り][通常論文]
  • Shotaro Uto, Takenobu Toyota, Haruhito Shimoda, Kazutaka Tateyama, Kunio Shirasawa
    ANNALS OF GLACIOLOGY, VOL 44, 2006 44 253 - + 2006年 [査読有り][通常論文]
     
    Recent observations have revealed that dynamical thickening is dominant in the growth process of sea ice in the southern Sea of Okhotsk. That indicates the importance of understanding the nature of thick deformed ice in this area. The objective of the present paper is to establish a ship-based method for observing the thickness of deformed ice with reasonable accuracy. Since February 2003, one of the authors has engaged in the core sampling using a small basket from the icebreaker Soya. Based on these results, we developed a new model which expressed the internal structure of pack ice in the southern Sea of Okhotsk, as a one-dimensional multilayered structure. Since 2004, the electromagnetic (EM) inductive sounding of sea-ice thickness has been conducted on board Soya. By combining the model and theoretical calculations, a new algorithm was developed for transforming the output of the EM inductive instrument to ice + snow thickness (total thickness). Comparison with total thickness by drillhole observations showed fair agreement. The probability density functions of total thickness in 2004 and 2005 showed some difference, which reflected the difference of fractions of thick deformed ice.
  • Shotaro Uto, Haruhito Shimoda, Shuki Ushio
    ANNALS OF GLACIOLOGY, VOL 44, 2006 44 281 - + 2006年 [査読有り][通常論文]
     
    Sea-ice observations have been conducted on board icebreaker Shirase as a part of the scientific programs of the Japanese Antarctic Research Expedition. We summarize these to investigate spatial and interannual variability of ice thickness and snow depth of the summer landfast ice in Lutzow-Holm Bay, East Antarctica. Electromagnetic-inductive observations, which have been conducted since 2000, provide total thickness distributions with high spatial resolution. A clear discontinuity, which separates thin first-year ice from thick multi-year ice, was observed in the total thickness distributions in two voyages. Comparison with satellite images revealed that such phenomena reflected the past break-up of the landfast ice. Within 20-30 km from the shore, total thickness as well as snow depth decrease toward the shore. This is due to the snowdrift by the strong northeasterly wind. Video observations of sea-ice thickness and snow depth were conducted on 11 voyages since December 1987. Probability density functions derived from total thickness distributions in each year are categorized into three types: a thin-ice, thick-ice and intermediate type. Such interannual variability primarily depends on the extent and duration of the successive break-up events.
  • Kazuki Nakamura, Hiroyuki Wakabayashi, Shotaro Uto, Kazuhiro Naoki, Fumihiko Nishio, Seiho Uratsuka
    ANNALS OF GLACIOLOGY, VOL 44, 2006 44 261 - + 2006年 [査読有り][通常論文]
     
    We investigated the feasibility of using multi-polarization synthetic aperture radar (SAR) data to estimate the thickness of undeformed first-year ice. Analysis of the radar signatures for the C- and L-bands showed that the correlation between the ice thickness and VV-to-HH backscattering ratio is larger than the correlation between the ice thicknesses and the backscattering coefficients. This is in part because the ice surface salinity and hence the surface reflection coefficient decreases as the ice thickens. The backscattering ratio had low sensitivity to the small-scale ice surface roughness for the C-band and is almost independent of roughness at L-band. Given that the ratio is most sensitive to ice surface dielectric constants, which depend on salinity, we developed an algorithm for retrieving the ice thickness that is based on the backscattering ratio and on the integral-equation-method (IEM) surface scattering model. Comparison of the observed and estimated ice thicknesses showed that the correlation was much better when the thicknesses were estimated using the backscattering ratio than when the backscattering coefficient was used directly. The algorithm also performed better than previous retrievals using an empirical technique.
  • K Nakamura, H Wakabayashi, Shotaro Uto, K Naoki, F Nishio, S Uratsuka
    IGARSS 2005: IEEE International Geoscience and Remote Sensing Symposium, Vols 1-8, Proceedings 4026 - 4029 2005年 [査読有り][通常論文]
     
    To investigate the possibilities of multi-polarization synthetic aperture radar (SAR) data to monitor sea-ice, we derived the relationship between polarization characteristics and the physical parameters of the sea-ice. We discuss the polarization characteristics of the backscattering coefficients of the sea-ice and then describe the sea-ice thickness by comparing the corresponding backscattering coefficient for each polarization with the physical parameters of the ice. We propose a retrieval algorithm for sea-ice thickness, which apply a backscattering ratio to estimate the thickness of the sea-ice. This ratio is calculated using a surface scattering model, which cancels the effect of roughness on backscattering The method was validated using the Advanced SAR (ASAR) onboard ENVISAT satellite observation data obtained at ground-truth sites.
  • Koh Izumiyama, Shigeo Kanada, Shotaro Uto, Natsuhiko Otsuka
    Proceedings of the International Conference on Port and Ocean Engineering under Arctic Conditions, POAC 2 863 - 872 2005年01月01日 [査読有り][通常論文]
     
    A study was made to develop an oil recovery unit in ice. The oil recovery in the unit is based on a concept to use air bubbles to separate oil from ice. Series of laboratory tests were performed to show the unit works effectively in various ice conditions.
  • Koh Izumiyama, Daisuke Wako, Haruhito Shimoda, Shotaro Uto
    Proceedings of the International Conference on Port and Ocean Engineering under Arctic Conditions, POAC 635 - 646 2005年01月01日 [査読有り][通常論文]
     
    Model tests of a ship in ice were performed. Ice load acting on the model hull was measured using a pressure sensing system. The model was equipped with podded propulsors and tested in a free-running mode. Turning tests as well as straight-going tests were performed. This paper presents the results of the test and discusses the difference of ice load between the turning and straight-going modes.
  • Shotaro Uto, Shuji Oka, Chikahisa Murakami, Tadanori Takimoto, Koh Izumiyama
    Proceedings of the International Conference on Port and Ocean Engineering under Arctic Conditions, POAC 2 635 - 646 2005年01月01日 [査読有り][通常論文]
     
    The authors conducted the short-term measurement of ice load exerted on the hull of icebreaker PM Teshio of Japan Coast Guard in 1999. Measurements were conducted in the selected vast ice floes in the south Sea of Okhotsk, near the coast of Hokkaido, Japan. Local ice load experienced by six transverse frames were measured using a pair of shear strain gauges. The measured maximum ice load attains to about 750kN/m, which is above the design ice load specified by the class IA-Super in the Finnish-Swedish Ice Class Rules. This sporadic event was observed in the bow area during the continuous icebreaking of 0.49m-thick ice. The magnitude and distribution of local ice load was discussed in relation to the icebreaking mode, propulsion power, and advancing speed.
  • 宇都正太郎, 下田春人, 泉山耕, 牛尾収輝, 青木茂, 橋田元, 若林裕之, 西尾文彦
    南極資料 48,165-179  2004年11月 [査読有り][通常論文]
  • K Izumiyama, S Uto, S Sakai
    INTERNATIONAL JOURNAL OF OFFSHORE AND POLAR ENGINEERING 14 3 169 - 175 2004年09月 [査読有り][通常論文]
     
    A study was undertaken regarding the formation of the so-called oil-ice sandwich, a phenomenon in which oil placed underneath an ice cover is entrapped in ice under freezing conditions. The study was a part of a larger research project on the behaviour and recovery method of oil in ice-covered waters. Laboratory tests were performed to study the ice growth under the oil layer. A numerical calculation that takes into account convective heat transfer through the oil layer agreed well with the experimental results. This was an attempt to predict the formation of an oil-ice sandwich in field conditions.
  • 牛尾収輝, 宇都正太郎, 泉山耕, 下田春人, 鮎川勝
    南極資料 48,180-190  2004年 [査読有り][通常論文]
  • K Izumiyama, S Uto, S Kanada, S Kioka, S Sakai
    PROCEEDINGS OF THE FOURTEENTH (2004) INTERNATIONAL OFFSHORE AND POLAR ENGINEERING CONFERENCE, VOL 1 910 - 914 2004年 [査読有り][通常論文]
     
    Results of a study on the oil spreading under ice are presented. The final objective of the study was to give the estimate of oil area spilled under an ice cover in field conditions. Three different approaches of numerical simulation, laboratory test and field measurement were taken in this study. Numerical simulation was performed to calculate oil spreading under ice in field conditions. A theory to calculate the oil area is given. Discussion is made on the comparison of the theory and the results of the laboratory test and numerical simulation.
  • K Tateyama, S Uto, K Shirasawa, H Enomoto
    PROCEEDINGS OF THE FOURTEENTH (2004) INTERNATIONAL OFFSHORE AND POLAR ENGINEERING CONFERENCE, VOL 1 806 - 812 2004年 [査読有り][通常論文]
     
    Indirect ice and snow thickness measurements were carried out for the winter and spring Antarctic sea ice by using the electromagnetic-inductive (EMI) device on the East Antarctic pack ice area. This study investigated the effect of saline slush snow layer over the sea ice and seawater-filled gap to the snow and sea ice thickness measured by EMI. A result shows underestimations of EMI thickness, which might be caused by high conductive seawater-filled gaps between ice floes, appeared on thicker ice over 3.5 m. This study improved the validity of applying a multi-rafted ice model for these ice conditions.
  • Ship-borne electromagnetic induction sounding of sea ice thickness in the Arctic during Summer 2003
    白澤邦男, 舘山一孝, 高塚徹, 宇都正太郎
    Polar Meteorology and Glaciology 20 53 - 61 2003年 [査読有り][通常論文]
  • K Izumiyama, S Uto, S Sakai
    PROCEEDINGS OF THE THIRTEENTH (2003) INTERNATIONAL OFFSHORE AND POLAR ENGINEERING CONFERENCE, VOL 2 268 - 273 2003年 [査読有り][通常論文]
     
    A study was made on the formation of oil-ice sandwich, a phenomenon in which oil placed underneath an ice cover is entrapped in ice under freezing condition. The study was made as a part of a larger research project on the behaviour and recovery method of oil in ice-covered waters. Laboratory tests were performed to study the ice growth under the oil layer. Numerical calculation that takes into account the convective heat transfer through the oil layer agreed well with the experimental results. It was attempted to predict the formation of oil-ice sandwich in field conditions.
  • Sea Ice Thickness and Snow Depth Distribution of the Summer Land-fast Ice in Lützow-Holm Bay, East Antarctica
    宇都 正太郎他
    Proceedings of the 17th POAC 1 175 - 186 2003年 [査読有り][通常論文]
  • K Riska, S Uto, J Tuhkuri
    COLD REGIONS SCIENCE AND TECHNOLOGY 34 3 209 - 225 2002年05月 [査読有り][通常論文]
     
    The response of a multiplate ship hull plating under ice loading is studied both experimentally and theoretically. In the theoretical work, the frames are assumed to be rigid but the plates between the frames are flexible. In addition, the ice, which puts a patch-like loading on the plating, is assumed to be compliant. This ice-structure contact is modelled as a framed structure on a Winkler foundation. In the experimental work, the response of framed structures under ice loading was studied. Structures with different plate thickness were used. It is shown that the spanwise pressure distribution in a plate is determined by the rigidity ratio between ice and the plate: lower plate rigidity induces a deduction in ice pressure at the mid-span area. The plate stresses depend on the rigidity ratio and also on the aspect ratio of the plate. (C) 2002 Elsevier Science B.V. All rights reserved.
  • 館山一孝, 榎本浩之, 豊田威信, 宇都正太郎
    Polar Meteorology and Glaciology 16 16 15 - 31 国立極地研究所 2002年 [査読有り][通常論文]
     
    This study presents the findings of research into the correlation between sea ice thickness and passive microwave radiation. In-situ sea ice thickness samples were obtained from video observations by the icebreaker Soya during 1996-1998 and surface feature observations in 1997 by the visible and near-infrared radiometer AVNIR mounted on the ADEOS satellite. These sea ice thickness data were binned into grid cell data of the satellite microwave radiometer SSM/I for the same location, and averaged to provide an average ice thickness for a grid cell. In order to survey the relationship between sea ice thickness and microwave radiation, two sea ice classification parameters for SSM/I were investigated as to their ability to estimate sea ice thickness. One sea ice classification parameter is the Polarization Ratio (PR), which was developed for a seasonally ice covered area and can distinguish three ice types: new ice, young ice, and first-year ice. Another parameter is the ratio between 37GHz vertical polarization and 85GHz vertical polarization (R_<37V/85V>). It can distinguish fast ice in addition to the three ice types that can be distinguished by the PR. These parameters showed correlation coefficients with in-situ sea ice thickness, -0.77 and 0.67, respectively, in this study. Estimated sea ice thickness derived from multiple regression analysis using PR and R_<37V/85V> showed good correlation (R=0.81) with in-situ sea ice thickness.
  • Ship-based Sea Ice Observations in Lützow-holm Bay, East Antarctica
    宇都正太郎他
    Proceedings of the 16th IAHR Ice Symposium 2 218 - 224 2002年 [査読有り][通常論文]
  • 泉山 耕, 宇都 正太郎, 金田 成雄, 下田 春人
    海洋開発論文集 16 197 - 202 Japan Society of Civil Engineers 2000年 
    Model testing at an ice tank is an indispensable tool for the design of offshore structures or ships to be used in ice. Model ice is used to represent sea ice at model scale. Mechanical properties of model ice should be properly scaled down from those of sea ice so that results of model testing in ice are of significance. This paper discusses mechanical properties of model ice based on data obtained at the ice tank of Ship Research Institute.
  • K Izumiyama, D Wako, S Uto
    ICE IN SURFACE WATERS, VOL 2 917 - 922 1999年 [査読有り][通常論文]
     
    indentation tests were performed at an ice model basin. A flat indentor was used in the tests. A new type of pressure sensing system was used in the tests to measure ice load distribution at the ice-indentor interface. Tests were performed for a wide range of the indentation speed. This paper describes the outline of the pressure sensing system and presents the results of measurement of the ice force distribution indentor. Discussion will be made on the influence of indentation speed on the ice force distribution.
  • Consideration on Accuracy of the Full-Scale Thrust Measurement in Ice by Strain Gauges
    宇都正太郎, 田村兼吉, 成田秀明
    Proceedings of the 18th International Conference Offshore Mechanics and Arctic Engineering 1999年 [査読有り][通常論文]
  • Ship-based Sea Ice Observations in the Southernmost Part of the Sea of Okhotsk
    UTO Shotaro
    Proceedings of the 15th International Conference on Port and Ocean Engineering under Arctic Conditions 1999年 [査読有り][通常論文]
  • K Izumiyama, S Uto, S Narita, R Tasaki
    ICE IN SURFACE WATERS, VOL 1 419 - 426 1998年 [査読有り][通常論文]
     
    Spreading behaviour of oil under an ice cover is studied Laboratory experiment was performed at an ice model basin to simulate the problem. Theoretical treatment of the problem was also made. Theoretical solutions are obtained by modifying a theory by Yapa so that they include effects of interfacial tension on the spreading behaviour of oil slick as well as gravity and viscous force. The new theory well explains the results of the present and past experiments. The theory gives a non-dimensional parameter governing the spreading behaviour of spilled oil under an ice cover.
  • Toshiyuki Kano, Takahiro Majima, Shotaro Uto, Koh Izumiyama
    Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE 4 201 - 208 1997年01月01日 [査読有り][通常論文]
     
    The Japan Maritime Safety Agency conducted full-scale experiments of three types of Patrol Vessels in ice in cooperation with the Japan Ship Research Institute at the sea of Okhotsk in the winter of 1996, which aimed to confirm the performance of the new Ice-breaking PM 'TESHIO' that was built in the autumn of 1995 and to develop rational design technology and operation in ice of Ice-breaker. Other than PM 'TESHIO', Ice-breaking Patrol Vessel PLH 'SOYA' and Ice-worthy PM 'YUBARI' joined the full-scale experiments in ice. Tests were continuous ice-breaking, ramming and stopping performance, turning capability, Zigzag course manoeuvrability and coordinated ice-breaking operation. Monitoring ice condition of the experiments was carried out. This paper describes the evaluation of performance of PM 'TESHIO' through the results of the full scale experiments and discusses the comparison of the performance of PM 'TESHIO' with that of PLH 'SOYA' and PM 'YUBARI' in ice.
  • Shotaro Uto, Haruhito Shimoda, Koh Izumiyama
    Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE 4 225 - 232 1997年01月01日 [査読有り][通常論文]
     
    'PM TESHIO' was delivered to the Japan Maritime Safety Agency in October 1995 as the second patrol vessel with icebreaking capability. Full-scale experiments were conducted in February 1996 in ice in the Sea of Okhotsk. Ship Research Institute conducted the model tests in ice and in open water while its design and construction were in process. This paper describes the model-ship comparison of the propulsive performance of 'PM TESHIO' in continuous icebreaking mode. The propulsion coefficient is decomposed into three factors, which imply the effect of the propulsor open characteristics, the propulsor overload condition, and the propulsor/ice interaction, respectively. A rational procedure is presented for determining each factor in model-scale by the results of model tests. The scale effect for the last factor is considered by comparing the frequency of the propulsor/ice interaction and the output power of the main engine between in full-scale and model-scale.
  • Koh Izumiyama, Shotaro Uto, Kenkichi Tamura, Susumu Kishi, Satoru Ishikawa, Hajime Yamaguchi
    Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE 4 25 - 32 1997年01月01日 [査読有り][通常論文]
     
    An R & D project of a cargo ship for the Northern Sea Route was carried out in Japan for the period of 1993 - 1995. In the first year of the project a preliminary design of the NSR cargo ship was made. The designed ship was 180 m in over all length, 24 m in width and 8 m in full loaded depth. The vessel was designed to have a 24,000 HP powered single propeller to go through the ice up to 1.2 m thick in the continuous ice-breaking mode. A series of model tests followed the preliminary design to find the optimum hull form for the NSR cargo ship. Models of various hull forms, four forms for the bow and three for the stern, were designed and tested. Both the conventional and ducted propellers were tested. Resistance test, self-propulsion test and turning test were carried out in level ice sheet. Models were also tested in ridged ice and in water. Based on test results, evaluation were made for the hull forms to find the optimum one.
  • Koh Izumiyama, Shotaro Uto
    Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE 4 431 - 436 1997年01月01日 [査読有り][通常論文]
     
    Indentation tests were performed at an ice tank to study dynamic ice loading on a structure. A flat indentor with a compliant foundation was used for the test. Three basic modes of response of indentor were observed in the test. They are quasi-static response, steady-state vibrations and decayed response. Discussions are made on the transition from the quasi-static response to the steady-state vibrations using the concept of Strouhal number. For the steady-state vibrations, it is shown that acceleration of the indentor can be given as a function of indentation speed and natural frequency of indentor. It is shown that the transition between the steady-state vibrations and decayed response can not be explained only by the Strouhal number but affected by other parameters.
  • Haruhito Shimoda, Mitsuo Yoshida, Shotaro Uto, Koichi Koyama
    Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE 4 217 - 224 1997年01月01日 [査読有り][通常論文]
     
    Full-scale trials of the patrol vessel 'PLH SOYA' in ice has been conducted since 1991 at the southern part of the Sea of Okhotsk. The objectives of the trials are to establish the database of sea ice conditions and to evaluate ship manoeuvrability in ice. Ice thickness and concentration were measured by the onboard VTR system. The probability density of ice thickness distribution follows a negative exponential form against the ice thickness beyond a particular value of thickness. The average ice concentration showed good agreement with that by the satellite observation. Manoeuvrability of 'PLH SOYA' was evaluated by the turning capability test and the zigzag course stability test. In small ice floes, turning capability is expressed as a function of ice volume, which is the product of ice thickness and concentration. On the other hand, it is expressed as a function of the square of the ice thickness in big ice floes.
  • Toshiyuki Kano, Takahiro Majima, Shotaro Uto, Koh Izumiyama
    Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE 4 209 - 215 1997年01月01日 [査読有り][通常論文]
     
    The Japan Maritime Safety Agency conducted full-scale experiments of three types of Patrol Vessels in ice in cooperation with the Japan Ship Research Institute at the sea of Okhotsk in the winter of 1996, which aimed to confirm the performance of a new Ice-breaking patrol vessel that was built in the autumn of 1995 and to develop rational design technology and operation in ice of Ice-breaker. This paper describes the evaluation of resistance of these vessels in level ice through the full-scale stopping performance tests and this evaluated value is compared with the estimated value by model test. And the differences of the performance on these vessels are discussed.
  • 田村兼吉, 泉山耕, 宇都正太郎, 下田春人, 岸進
    日本造船学会論文集 180 113 - 122 日本造船学会 1996年12月 [査読有り][通常論文]
     
    The problem of propeller-ice interaction is very important for ice going vessels, and this phenomenon is not cleared yet. Since the classical works of Jagodkin in 1963, some calculation models have been presented, but none of them can be widely accepted. One of this reason is that quite a few full-scale measurement data used to verify a model can be seen. Besides, the nozzle propeller has been used for propulsion system of icebreaker recently because of its excellent features, but full-scale measurement data of the nozzle propeller are rare. This paper describes the results of full-scale data of nozzle propeller concerning propeller-ice interaction. These data were obtained in the full-scale trials of the patrol icebreaker "TESHIO", which were conducted in the sea of Okhotsk in February 1996. Some strain gauges were attached on the port side shaft, so the regular component and the fluctuations component of shaft thrust, shaft torque and shaft revolution were measured while the ship was going in ice sea. The maximum fluctuations component of shaft horsepower (SHP) was almost as same as the regular component of SHP. The interval of interaction was also proportional to the regular component of SHP. The comparison on the interval of interaction between full scale data and model test data were also shown. It shows the same tendency that the interval of interaction was shorter as the ice thickness become thicker.
  • 岸進, 宇都正太郎, 加納敏幸, 上園政裕, 川島義伸, 泉山耕
    日本造船学会論文集 180 99 - 112 日本造船学会 1996年12月 [査読有り][通常論文]
     
    The patrol icebreaker "TESHIO" was built and delivered to the Japan Maritime Safety Agency in Autumn 1995. Full-scale trials in ice were conducted at the Sea of Okhotsk in February, 1996. Several kinds of test were performed in order to confirm her performance such as continuous ice-breaking, ramming and stopping performance, turning capability and zigzag course manoeuvrability, and coordinated ice-breaking operation together with the patrol icebreaker "SOYA". While her design and construction were in process, series of model test were carried out both in ice and in ice-free water as the joint research project between Ship Research Institute, Ministry of Transport and NKK Corporation. At the ice model basins of the two organizations, comprehensive model tests in ice were conducted which included resistance and self-propulsion tests in various ice conditions, ramming and turning tests in level ice. This paper describes the results of model and full-scale tests of "TESHIO" and their correlation for both continuous ice-breaking and ramming performance. In order to predict the required BHP for the continuous ice-breaking in level ice, the propulsion coefficient was decomposed into three parts which denote effects of open water characteristics, overload and propulsor/ ice interaction, respectively. The thrust deduction coefficient obtained from towed propulsion tests in ice showed very good agreement with that from overload tests in ice-free water. The predicted BHP showed good agreement with the full-scale results when the effect of propulsor/ice interaction was taken into consideration. A prediction formula for ramming penetration distance was devised using an energy-based method. Correlation of both the model and full scale data to the prediction results showed that thrust loss due to the propulsor/ice interaction and the automatic overload protection control of the main engine had much influence on the prediction of ramming performance.
  • Experimental Study on Propulsive Performance of Icebreaker PLH “SOYA”
    宇都正太郎, 成田秀明
    Journal of the Kansai Society of Naval Architects, Japan 229 45 - 50 1996年 [査読有り][通常論文]
  • 舶用プロペラまわり粘性流場の尺度影響に関する基礎的研究
    宇都 正太郎
    関西造船協会論文集 222 33 - 40 1994年 [査読有り][通常論文]
  • Computation of Incompressible Viscous Flow Around a Marine Propeller -2nd Report : Turbulent Flow Simulation
    宇都 正太郎
    Journal of the Society of Naval Architects of Japan 173 67 - 76 1993年 [査読有り][通常論文]
  • 舶用プロペラまわり粘性流場計算へのCFDの応用-計算格子生成及びオイラー方程式を用いた非粘性計算-
    宇都 正太郎, 児玉良明
    関西造船協会論文集 218 171 - 180 1992年 [査読有り][通常論文]
  • Computation of Incompressible Viscous Flow Around a Marine Propeller
    宇都 正太郎
    Journal of the Society of Naval Architects of Japan 172 213 - 224 1991年01月 [査読有り][通常論文]
  • K IZUMIYAMA, H KITAGAWA, K KOYAMA, S UTO
    POAC 91, VOL 1 1 155 - 166 1991年 [査読有り][通常論文]
     
    Model tests were carried out for a conical structure in ice. Crack pattern in the ice sheet was quantitatively analysed as well as ice forces on the model. The crack size and its effect on the ice force are discussed.
  • H KITAGAWA, K IZUMIYAMA, K KOYAMA, S UTO
    POAC 91, VOL II 2 623 - 634 1991年 [査読有り][通常論文]
     
    The ship model basin for hydrodynamic research has a long history. Since W. Froude carried out model experiments at his historic towing tank at Torquay, a number of ship model basins have been constructed in various countries. Investigations of instrumentation and experimentation for the basins have long been performed to improve accuracy in model testings and prediction of full scale performance of ships and marine structures. Short history of the ice tank still requires various systematic and long term studies of ice tank technologies. The Ship Research Institute has been conducting a systematic study to find reasonable methods of model testings at the ice tank. In this paper some results of experiments are presented and discussed on model ice properties and testings with ship models.
  • 複合格子法を用いた翼列まわり粘性流の数値計算
    宇都 正太郎, 児玉良明
    関西造船協会論文集 215 61 - 68 1990年 [査読有り][通常論文]
  • 宇都 正太郎
    Papers of Ship Research Institute 7 4 149 - 176 運輸省船舶技術研究所 1989年 [査読有り][通常論文]
     
    Computation of the two-dimensional incompressible turbulent flow around a wind section in cascade was made using the finite difference method. The computational scheme used in this paper is based on the Implicit Approximate Factorization scheme, which has been developed at the Ship Research Institute. The overlapping grid technique was used in order to generate well-conditioned, body-fitted coordinates for the complicated computational domain around a cascade wing section easily. The computed results were compared in two steps. Firstly, the comparative computational study between the present method and the higher-order boundary layer integral method was carried out and the merit and demerit of the present scheme were discussed in detail. Secondly, the comparison with experimental data (lift and drag coefficient) was made. The present method showed reasonable agreement with them.

その他活動・業績

受賞

  • 1983年03月 大阪大学 楠本賞
     
    受賞者: 宇都 正太郎

教育活動情報

主要な担当授業

  • 大学院共通授業科目(一般科目):複合領域
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : 北極域、地球環境、温暖化、気候変動、炭素循環、水循環、人間活動、永久凍土、北極域航路、国際政治、持続的開発 Arctic, Global environment, Global warming, Climate change, Ecosystems, Human activity, Permafrost, Northern Sea Route, Global politics, Sustainable development
  • 北極域総論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 環境科学院
    キーワード : 北極域、地球環境、温暖化、気候変動、炭素循環、水循環、人間活動、永久凍土、北極域航路、国際政治、持続的開発 Arctic, Global environment, Global warming, Climate change, Ecosystems, Human activity, Permafrost, Northern Sea Route, Global politics, Sustainable development

大学運営

委員歴

  • 2018年04月 - 現在   文部科学省   南極輸送計画委員会委員
  • 2017年09月 - 2021年06月   国際試験水槽会議   理事
  • 2017年06月 - 2021年06月   日本船舶海洋工学会   理事
  • 2019年06月 - 2021年05月   日本船舶海洋工学会   副会長、東部支部長
  • 2018年10月 - 2020年09月   日本学術会議   特任連携会員


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