Wataru Fujimoto

Wataru Fujimoto
Nippon Kaiji Kyokai · Research Institute

Doctor of Philosophy

About

12
Publications
1,122
Reads
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88
Citations
Introduction
I'm currently working on application of ocean wave science for maritime safety.
Additional affiliations
April 2020 - April 2020
Nippon Kaiji Kyokai
Position
  • Researcher
April 2018 - March 2020
MS&AD InterRisk Research&Consulting. Inc.
Position
  • Researcher
Education
April 2015 - March 2018
The University of Tokyo
Field of study
  • Ocean Engineering

Publications

Publications (12)
Article
Full-text available
The presence of coherent wave groups in the ocean has been so far postulated but still lacks evidence other than the indication from the radar images. Here, we attempt to reconstruct a wave field to monitor the evolution of a directional wave group based on a phase resolving two-dimensional non-linear wave model constrained by the stereo images of...
Article
Freak/rogue waves are considered to be the causes of marine accidents and their generation mechanism is closely related to the formation of wave groups. However, observations that capture the spatiotemporal evolution of coherent wave groups in directional windsea are rather limited. The paper presents a new technique known as the surface wave recon...
Conference Paper
A stereo camera system was installed facing Southeast at the observational tower owned by the University of Tokyo in the Sagami Bay, Japan. The three-dimensional wave fields were reconstructed from the stereo images, which were successfully captured from April 2017 until now, by using an open source software WASS (Waves Acquisition Stereo System)....
Article
Full-text available
Amplitude modulation of a propagating wave train has been observed in various media including hydrodynamics and optical fibers. The notable difference of the propagating wave trains in these media is the magnitude of the nonlinearity and the associated spectral bandwidth. The nonlinearity and dispersion parameters of optical fibers are two orders o...
Article
Two freak waves were observed a day apart in October 2009 at a 5000-m deep moored station in the northwest Pacific Ocean. As the typhoon passed by, the wave system transitioned within a day from a narrow and unimodal spectrum to the broad and bi-modal spectrum. The occurrence probability of a freak wave is known to increase due to a modulational in...
Article
A new wave generation method, called HOSM-WG, is presented in this paper. The method utilizes the precomputed spatially periodic wave field based on the higher-order spectral method (HOSM) simulation to calculate the wave-maker signals. The spatially periodic wave fields were reproduced in a rectangular basin with 382 wave makers on the peripheral....
Conference Paper
This study proposes ideas to reproduce freak waves from observational data. The reproduced data will apply to investigations on freak wave impact to offshore structures. Four-dimensional variational method (4DVAR) was used for the freak wave reproduction. Under a dynamical constraint, 4DVAR minimizes the squared error between observation and model...
Article
Full-text available
Resource assessment is an essential step in the reconnaissance to feasibility study stages of marine renewable energy development. However, minimization of uncertainties associated with the estimation requires that data be provided at a sufficiently high resolution and duration long enough to include effects of climate variation. This paper describ...
Article
The University of Tokyo and JAMSTEC have conducted state-of-the-art wave and current resource assessments to assist with generator site identification and construction in Japan. These assessments are publicly-available and accessible via a web GIS service designed by WebBrain that utilizes TDS and GeoServer software with Leaflet libraries. The web...
Conference Paper
The local shapes of freak waves are essential to estimate responses of ships or offshore structures by freak waves for limit state design or maritime accident survey. It is known that freak waves deform like a crescent and their trough depth become asymmetric in directional and irregular wave fields. Meanwhile, Class I & II instabilities also affec...
Conference Paper
A method to produce freak waves with arbitrary spectrum in a fully directional wave basin is presented here. This is an extension of Waseda, Houtani and Tanizawa at OMAE 2013[1], which used “HOSM-WG” based on the higher-order spectral method (HOSM). We used the following three methods to improve the HOSM-WG in [1]: “separation of free waves from bo...
Conference Paper
The local properties of freak waves, such as geometry and particle velocities, are still to be investigated and are essential in the limit state design of ships or offshore structures. We have focused on two factors for this research. The first is nonlinearity higher than 3rd order since local steepness around freak waves will be large. The 4th ord...

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