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Hashimoto, Noriaki
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Aerospace Engineering Decision Sciences, Operations Research & Management Engineering Industrial & Manufacturing Engineering Mechanical Engineering

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Transformation of Directional Wave Spreading in the Surf Zone Using Video Image Data Zikra, Muhammad; Hashimoto, Noriaki; Yamashiro, Masaru; Suzuki, Kojiro
Journal of Ocean, Mechanical and Aerospace -science and engineering- Vol 4 No 1 (2014): Journal of Ocean, Mechanical and Aerospace -science and engineering- (JOMAse)
Publisher : International Society of Ocean, Mechanical and Aerospace -scientists and engineers- (ISOMAse)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36842/jomase.v4i1.517

Abstract

In present study, video images technique is used to investigate the transformation of the directional wave spreading in shallow water. The technique is based on time series of the pixel brightness on video images. The Bayesian Directional Method is conducted in estimating the directional wave spectrum for evaluating the change of the directional wave spreading in the surf zone area. Video image data recorded at Hasaki beach in Japan are used in the analysis. Estimation of principle direction and spreading parameter in the surf zone regions indicated that principle directions at peak frequency are not strongly affected by wave breaking process. In contrast, the broadenings of directional spreading were observed when the waves start breaking on the sand bar and toward the shore area.
Non-Linear Inversion Method to Derive Bathymetry from Video Images Zikra, Muhammad; Hashimoto, Noriaki; Suzuki, Kojiro; Plant, Nathaniel G.
Journal of Ocean, Mechanical and Aerospace -science and engineering- Vol 17 No 1 (2015): Journal of Ocean, Mechanical and Aerospace -science and engineering- (JOMAse)
Publisher : International Society of Ocean, Mechanical and Aerospace -scientists and engineers- (ISOMAse)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36842/jomase.v17i1.455

Abstract

This study investigates the capabilities of optical remote sensing to monitor bathymetry in nearshore area using video images. The technique is designed to extract wave number components based on variation of intensity of brightness at each pixel in the images using cross-spectral correlation approach. This approach is based on pixel array analysis that utilizes a nonlinear inverse method 'Levenberg-Marquardt’. The technique is applied to the data collected at Hasaki beach in Japan from August to December 2006. The results indicate that the cross-spectral correlation approach have the capability to derive wave number estimate from time series data of video images with small rms errors (0.0342-0.0421). Also, the estimate of nearshore bathymetry is proved reasonable accurate near shoreline and breaking area where the differences between estimated and survey water depth are less than 10-30 cm.
Projection of Ocean Wave Climate Change Based on Numerical Simulations Zikra, Muhammad; Hashimoto, Noriaki; Mitsuyasu, Kodama
Journal of Ocean, Mechanical and Aerospace -science and engineering- Vol 21 No 1 (2015): Journal of Ocean, Mechanical and Aerospace -science and engineering- (JOMAse)
Publisher : International Society of Ocean, Mechanical and Aerospace -scientists and engineers- (ISOMAse)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36842/jomase.v21i1.445

Abstract

This study aims to analyze global wave climates of present and future time by using the WAM model. The analysis is performed based on wind climate data from the JMA/MRI-AGCM3.2 climate change projection. We analyze two 6-hourly wind data sets, covering two periods: the present climate ranging from 1979-2003 and future climate extending from 2075-2099. These wind data are used to implement the WAM model for producing the outputs of wave characteristics. Subsequently, the outputs from each period were used to study global wave climate in the future. The analysis showed that the wave climate is strongly dependent on the geographical position of regions from mid to high latitude and low latitude. This includes regions where the climate induced changes for present to future climate. The largest increases of significant wave height which reached approximately 5% occur in the southern parts of the Indian, Pacific and Atlantic Oceans and in the Antarctic Ocean. The decreases in the same magnitude around 5% occur especially in the North Atlantic Ocean.
Co-Authors Mitsuyasu, Kodama Muhammad Zikra Plant, Nathaniel G. Suzuki, Kojiro Yamashiro, Masaru