MURAI Motohiko

Affiliation

Faculty of Environment and Information Sciences, Division of Artificial Environment and Information

Job Title

Associate Professor

Date of Birth

1970

Research Fields, Keywords

Very Large Floating Structure, Mega-float, Offshore structure, Offshore environment, Hydroelasticity, Hydrauric test, Uminokouen, Tidalland, Shell-digging, Human-activity in coastal zone, Utilization of Ocean Energy, Marine Renewable Energy, Ocean Renewable Energy

Mail Address

E-mail address

Related SDGs




The Best Research Achievement in Research Career 【 display / non-display

  • 【Published Thesis】 On the hydroelastic responses of a very large floating structure in waves  1999.12

    【Published Thesis】 Experimental and theoretical analysis of the wave decay along a long array of vertical cylinders  2002.04

The Best Research Achievement in the last 5 years 【 display / non-display

  • 【Published Thesis】 A Study on Electrical Power for Multiple Linear Wave Energy Converter Considering the Interaction Effect  2018.11

    【Published Thesis】 EXPERIMENTAL STUDY ON A 3-DIMENSIONAL HYDRO-ELASTIC DEFORMATION OF "UNDERWATER PLATFORM" WITH MULTI-TOWERS IN WAVES  2016.06

    【Published Thesis】 Hydrodynamic modelling of marine renewable energy devices: A state of the art review  2015.09

Graduating School 【 display / non-display

  •  
    -
    1993.03

    The University of Tokyo   Faculty of Engineering   Graduated

Graduate School 【 display / non-display

  •  
    -
    1995.03

    The University of Tokyo  Graduate School, Division of Engineering  Navalarchtects and Ocean engineerings  Master Course  Completed

Degree 【 display / non-display

  • Doctor of Engineering -  The University of Tokyo

Campus Career 【 display / non-display

  • 2007.04
    -
    Now

    Duty   Yokohama National UniversityFaculty of Environment and Information Sciences   Division of Artificial Environment and Information   Associate Professor  

  • 2001.04
    -
    2007.03

    Duty   Yokohama National UniversityResearch Institute of Environment and Information Sciences   Division of Social Environment and Information   Associate Professor  

  • 1999.04
    -
    2001.03

    Duty   Yokohama National UniversityGraduate School of Engineering   Associate Professor  

  • 2018.04
    -
    Now

    Concurrently   Yokohama National UniversityGraduate school of Engineering Science   Department of Mechanical Engineering, Materials Science and Ocean Engineering   Associate Professor  

  • 2017.04
    -
    Now

    Concurrently   Yokohama National UniversityCollege of Engineering Science   Department of Mechanical Engineering, Materials Science and Ocean Engineering   Associate Professor  

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External Career 【 display / non-display

  • 1997.08
    -
    1999.03

    Reserch Associate, University of Tokyo Faculty of Engineering Department of Naval Architecture and Ocean Engineering   Research Assistant  

Academic Society Affiliations 【 display / non-display

  • 2011.07
     
     
     

    Japanese Association for Coastal Zone Studies

Field of expertise (Grants-in-aid for Scientific Research classification) 【 display / non-display

  • Ocean environmental engineering

  • Hydromecanics

  • Ocean engineering

  • Naval and maritime engineering

 

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

  • 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

  • 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

  • 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

  • A Novel Conceptual Design of a Dynamically Positioned Floating Wind Turbine

    Shengwen Xu, Motohiko Murai, Xuefeng Wang, Kensaku Takahashi

    Journal of 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.

    DOI

  • 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

  • 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 ( J F O E S & J A S N A O E )    OES28 - 078   2020.09

    Joint Work

     View Summary

    In recent years, ocean renewable energy has attracted attention from the viewpoint of energy diversification. Japan has one of the world's largest exclusive economic zones, and its effective utilization is expected. In this study, we conducted experiments on the effects of the nozzle opening ratio, internal air volume and internal water level fluctuation of the OWC type wave power generator. However, the influence of the hydrodynamic force coefficient on the scale change of the OWC wave power generator has not been confirmed. In this study, we focused on the scale effect of the OWC type wave power generator model, and performed a forced oscillation test in an experimental water tank. For the model, we used 1/30, 1/60, and 1/120 of the size compared to the actual model, and compared the results to examine the scale effect. As a result of the analysis, it was found that the hydrodynamic coefficient was different for each of the scales, and the knowledge about the scale effect of the hydrodynamic coefficient in the OWC type wave power generator was obtained.

  • 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 ( J F O E S & J A S N A O E )    OES28 - 056   2020.09

    Joint Work

     View Summary

    One of the major issues in the introduction of offshore wind power generation is coordination with fishermen who use the ocean until now as so far. Currently, as a solution to the problem, there is an idea that the introduction of offshore wind turbines in cooperation with local fishermen will lead to the revitalization of local fisheries and aim to collaborate fishing. Here we treat "Floating offshore wind power generation cooperative with fisheries" and investigate the motion of a floating offshore wind turbine with a net of aquaculture cages. In this study, the dynamic characteristics of the net were examined by conducting experiments first, and based on the characteristics, a numerical analysis was performed on the motion of the floating body when the aquaculture net was attached to the floating offshore wind turbine.

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Works 【 display / non-display

  • Muti-arrays supported very large floating Structure

    Other 

    2000
     
     
     

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(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

  • ocean renewable energy

    APhydro2012  2012.09.04  

  • Ocean renewable energy

    Oceans2012  2012.05.22  

  • Ocean space utilozation

    2011.08  

  • Ocean space utilozation

    2011.08  

  • Ocean space utilization

    2011.05.18  

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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

  • 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