Research Career 【 display / non-display 】

Research Career 【 display / non-display 】

• A Study of a ocean space utilization

  Project Year：  -   

• Evaluation of Ocean Environment at Artificial tideland cosidering with human impacts

  Project Year：  -   

• Development of experiment methods on a very large floating structure in a very small water tank

  Project Year：  -   

• A Study on Hydroelastic behaviour of a Very Large Floating Structure

  Project Year：  -   

• Renewable energy in Ocean

  Project Year：  -   

Books 【 display / non-display 】

Books 【 display / non-display 】

• Ship Geometry and Fundamentals of Hydrostatics (Naval Architecture and Ocean Engineering Series 1)

  Ikeda Yoshiho, Yoshitaka Furukawa, Toru Katayama, Tokihiro Katsui, Motohiko Murai, Satoru Yamaguchi (Part： Joint Work )

  成山堂書店  2018.08 ISBN: 9784425714360

• Environmental Management of Marine Ecosystems

  Md. Nazrul Islam, Sven Erik Jorgensen (Part： Joint Work , Range: Inclusive Impact Index 'TripleI' )

  CRC Press  2018.03 ISBN: 9781498767729

  　View Summary

  https://www.crcpress.com/Environmental-Management-of-Marine-Ecosystems/Islam-Jorgensen/p/book/9781498767729

Thesis for a degree 【 display / non-display 】

Thesis for a degree 【 display / non-display 】

• 大型浮体式構造物の流力弾性挙動の推定法に関する研究

  村井基彦 

    1995.03  [Refereed]

  No Setting   Single Work

Papers 【 display / non-display 】

Papers 【 display / non-display 】

• Estimation of Maximum Bending Moment at FPSO Bow Considering Slamming in External Turret Mooring

  Ishihara Yuki, Kato Shunji, Murai Motohiko, Nakajima Yasuharu

  Journal of the Japan Society of Naval Architects and Ocean Engineers ( The Japan Society of Naval Architects and Ocean Engineers )  33 ( 0 )   87 - 96   2021.09  [Refereed]

  Joint Work

  　View Summary

  <p>The external turret system is widely used for mooring of Floating Production, Storage and Offloading system (FPSO). Slamming is one of important issues which should be considered for designing FPSOs because FPSOs must stay in the same area even if those are under harsh conditions such as a storm. In response to cases of accidents caused by slamming, such as Schiehallion, a series of research projects were conducted in Europe, which proposed that the simplified estimation method of maximum slam force; however, it was too simplified to be used for detailed design.</p><p>In this paper, we present the extreme value estimation of maximum bending moment including the slamming effect at the connection between the FPSO bow and the external turret lever. The foundation of the estimation method is based on the time-domain simulation by using the simulation model which was validated by comparing the results of the simulations with those of model tests. The simulation model was validated through comparison between model test results and the simulations. Two estimation methods for the expected value of 3 hour-maximum bending moment using the validated simulation model were investigated; one was the way of averaging maxima in multiple simulations, and another was due to extreme value analyses by four kinds of methods. As a result, the first method required more than 30 simulations; for the second method, the generalized Pareto distribution was the most suitable for extreme value analysis.</p>

  DOI CiNii

• A novel conceptual design of a dynamically positioned floating wind turbine

  Xu Shengwen, Murai Motohiko, Wang Xuefeng, Takahashi Kensaku

  OCEAN ENGINEERING ( Elsevier )  221   2021.02  [Refereed]

  Joint Work

  　View Summary

  Currently, all floating wind turbines served on the sea are positioned by the mooring system. A novel conceptual design of using the dynamic positioning system (DPS) to position the floating wind turbine is proposed in this paper. Certain benefit aspects of the proposed conceptual design are elaborated. A time domain simulation for the designed floating wind turbine is conducted to demonstrate its effectiveness. It is obtained from the results that approximately 1/2 of the generated energy is utilized by the DPS to keep the floating wind turbine positioned if current forces are not considered, while the ratio becomes 4/5 if current load effects are taken into account. Thus, the proposed conceptual design is demonstrated to be feasible in the view of conservation of energy. The impact of several primary design variables, such as the diameter of the wind turbine rotor, the diameter of the thruster and the wind speed, on the power ratio is specifically investigated. To make the conceptual design more convincible, several representative operational situations of the floating wind turbine in its lifetime are analyzed. It can be found that the situations that the consumed power is larger than the generated power can be effectively tackled by the stored hydrogen converted in the far long period of operation of the wind turbine in rated wind speed. Considering the proposed concept has particular benefits that cannot be replaced by conventional moored floating wind turbines, further research on the novel concept is warranted. （英訳）：Currently, all floating wind turbines served on the sea are positioned by the mooring system. A novel conceptual design of using the dynamic positioning system (DPS) to position the floating wind turbine is proposed in this paper. Certain benefit aspects of the proposed conceptual design are elaborated. A time domain simulation for the designed floating wind turbine is conducted to demonstrate its effectiveness. It is obtained from the results that approximately 1/2 of the generated energy is utilized by the DPS to keep the floating wind turbine positioned if current forces are not considered, while the ratio becomes 4/5 if current load effects are taken into account. Thus, the proposed conceptual design is demonstrated to be feasible in the view of conservation of energy. The impact of several primary design variables, such as the diameter of the wind turbine rotor, the diameter of the thruster and the wind speed, on the power ratio is specifically investigated. To make the conceptual design more convincible, several representative operational situations of the floating wind turbine in its lifetime are analyzed. It can be found that the situations that the consumed power is larger than the generated power can be effectively tackled by the stored hydrogen converted in the far long period of operation of the wind turbine in rated wind speed. Considering the proposed concept has particular benefits that cannot be replaced by conventional moored floating wind turbines, further research on the novel concept is warranted.

  Web of Science DOI

• Study on Power Generation of Single Point Absorber Wave Energy Converters (PA-WECs) and Arrays of PA-WECs

  Motohiko Murai, Qiao Li, Junki Funada

  Journal of Renewable Energy ( Elsevier )  164   1121 - 1132   2021.02  [Refereed]

  Joint Work

  　View Summary

  The effects of humanity’s carbon footprint deserve attention and remediation. The ocean can provide an abundant source of renewable energy instead of fossil fuels in the form of wave energy. However, wave energy collection needs to be comparable in terms of cost and efficiency to be considered a viable alternative. Point Absorber Wave Energy Converter (PA-WEC) is one method of capitalizing on the ocean’s wave energy. Past research provides methods for optimizing control force parameters for single PA-WECs. This paper provides methods for optimizing control force parameters for arrays of PA-WECs; optimization considers factors such as radiation hydrodynamic interactions, diffraction hydrodynamic interactions, array arrangements, and wave incident angles. In section 2, we outline the steps to determining optimal control forces. In section 3, we present numerical simulations of PA-WECs and compared the results between single PA-WEC systems and arrayed PA-WEC systems.

  DOI

• The Evaluation of Seakeeping of a Cylinder-shaped Floating Structure with Gyroscopic Motion Based on the Potential Fluid Theory

  Motohiko Murai,Xiaolei Liu

      2020.11

  Joint Work

• Short-Time Wave Force Prediction and Control Strategy for a Point-Absorber WEC

  Qiao Li, Motohiko Murai, Daisuke Kitazawa

  Journal of Ocean Engineering ( Elsevier )  218   2020.11  [Refereed]

  Joint Work

  　View Summary

  There are several numerical analyses for solving the hydrodynamic responses of a floating body in the time domain. Most of these provide a theoretical solution in the given irregular waves. However, the solution can be obtained only if accurate irregular waves represented by the wave spectrum are provided. Because we consider actual operation, we know that it is difficult to detect accurate irregular waves instantaneously as accuracy is required in most time domain analyses for the control force feedback to the system. This paper proposes a new method to predict the practical wave force from the displacement of waves of a floating body in the time domain analysis almost instantaneously. This method, that can be applied to predict forces in the wave energy converter with a linear electric generator, helps us to select the control force for higher conversion of electric power. We confirm the algorithm and examine its effectiveness used statistical database of real sea waves. We showed the limits of the range of application by ACL control algorithm and hybrid control algorithm under ideal conditions when considering physical motion restrictions and output restrictions that are always present in actual equipment.

  DOI

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Works 【 display / non-display 】

Works 【 display / non-display 】

• Muti-arrays supported very large floating Structure

  Other 

  2000

  　

  　

   

Academic Awards Received 【 display / non-display 】

Academic Awards Received 【 display / non-display 】

• The Best Paper Award 2020 of Japanese Association for Coastal Zone Studies

  2020.09.07   Japanese Association for Coastal Zone Studies   Trend and consideration on the changes in population density of short neck clam at 'Umino-Kouen'

  Winner： Motohiko MURAI

• OMAE 2019 Best Paper Award of Takeshi Kinoshita Honoring Symposium on Offshore Technology

  2020.08.07   ASME   Study on the Generated Power Changes by the Relation Between an Arrangement of an Array of Point Absorber Type WECs and an Incident Wave Angle (OMAE2020-95400)

  Winner： Motohiko Murai, Qiao Li, Junki Funada

• OMAE 2015 Best Paper Award of Ocean Space Utilization

  2016.06   ASME   Comparison of Weathervane Performance Between Two Types of FOWT Systems Moored to SPM (OMAE2015-41137)

  Winner： Kazuhiro Iijima, Yuiko Kuroda, Yasunori Nihei, Motohiko Murai

Grant-in-Aid for Scientific Research 【 display / non-display 】

Grant-in-Aid for Scientific Research 【 display / non-display 】

• Grant-in-Aid for Scientific Research(C)

  Project Year： 2018.04  -  2021.03  Investigator(s): Motohiko MURAI

• Grant-in-Aid for Scientific Research(C)

  Project Year： 2013.04  -  2016.03  Investigator(s): Motohiko Murai

• Grant-in-Aid for Scientific Research(B)

  Project Year： 2012.04  -  2016.03  Investigator(s): Makoto Arai

• Grant-in-Aid for Scientific Research(B)

  Project Year： 2008.04  -  2011.03 

• Grant-in-Aid for Scientific Research(B)

  Project Year： 2008.04  -  2011.03 

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Presentations 【 display / non-display 】

Presentations 【 display / non-display 】

• Study on scale effect of fluid force coefficient in water tank experiment simulating OWC type wave power generator

  Motohiko MURAI, Masaki Fujioka, Takuya Nagashima

  The 28th Ocean Engineering Symposium  2020.09.29   J F O E S & J A S N A O E

• Study on scale effect of fluid force coefficient in water tank experiment simulating OWC type wave power generator

  Motohiko MURAI, Sho Sakamoto, Takumi Nakajima, Takero Yoshida, Qiao Li, Daisuke Kitazawa

  The 28th Ocean Engineering Symposium  2020.09.29   J F O E S & J A S N A O E

• EXPERIMENTAL STUDY OF SLAM FORCES ON EXTERNAL TURRETS WITH DIFFERENT TOP ANGLES

  Yuki Ishihara , Motohiko Murai, So Nakanishi, Shunji Kato, Yasuharu Nakajima

  OMAE2020  2020.08.04   ASME

• The Evaluation of Seakeeping of a Cylinder-shaped Floating Structure with Gyroscopic Motion Based on the Potential Fluid Theory

  Motohiko Murai,Xiaolei Liu

  Annual conf. of the Japan Society of Naval Architects and Ocean Engineers  2020.06   the Japan Society of Naval Architects and Ocean Engineers

• ocean renewable energy

  APhydro2012  2012.09.04  

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Council/Academic activity outside the university 【 display / non-display 】

Council/Academic activity outside the university 【 display / non-display 】

• JASNAOE Marine Environment Committee

  2019.04

  　

  　

  Society  

• ISSC Specialist Committee on Ocean Space Utilization

  2018.09

  　

  　

  Society   member

• IEC（International Electrotechnical Commission） TC-114(Marine energy - Wave, tidal and other water current converters) PT 62600-202

  2015.02

  　

  　

  Others   member

• ITTC Specialist Committee on Testing of Marine Renewable Devices

  2011.09

  -

  2017.09

  Others   Member

Social Contribution(Extension lecture) 【 display / non-display 】

Social Contribution(Extension lecture) 【 display / non-display 】

• Lecture on "Design and Analysis of Offshore floating Wind Turbine" supported by Global Initiative of Academic Network (GIAN)

  Global Initiative of Academic Network by INDIA Government  （Mangaluru, India） 

  2019.09

  　

  　

• World NAOE Forum 2013 &International Symposium on Developments in Marine and Offshore Renewable Energy

  2013.11