Naofumi Yamaguchi

Ibaraki University

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Ripple Formation and Grain Sorting with Multiple-sized Sand: a Report of the Preliminary Wave-flume Experimentation

京都大学防災研究所年報. B = Disaster Prevention Research Institute Annuals. B (2007)

Naofumi Yamaguchi Hideo Sekiguchi

Synopsis Three series of wave-flume experiments were performed for the purposes of assessing capability of a wave-flume and investigating an effect of multiple-sized sand on ripple formation. The first series of experiments were performed under fixed-bed condition, indicating that the measured performance of wave height-to-stroke ratio was only slightly smaller than theoretically expected. The other two series with multiple-sized sand beds facilitated the following: (1) the critical value of the mobility number for ripple formation with multi-sized sands may be larger than the critical value with uniform sands; and (2) as more asymmetrical oscillatory flow, the difference of grain size between onshore-slope and offshore-slope appeared more prominently.

Flume

Wave flume

Ripple marks

Wave height

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Citations (1)

Basal slip plane of the Kurotaki unconformity in the Boranohana area along the Pacific coast of the Boso peninsula, Central Japan

Island Arc (2011)

Makoto Otsubo Naofumi Yamaguchi Shin-ichi Nomura Nozomi Kimura Hajime Naruse

Peninsula

Geological survey

10.1111/j.1440-1738.2011.00772.x

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Citations (3)

Effect of sediment supply on geometry of wave ripples: preliminary results of flume experiment

Journal of the Sedimentological Society of Japan (2022)

Naofumi Yamaguchi Toshifumi Taki Tomohiro Sekiguchi

ウェーブリップルの形状への堆積物供給の影響を調べるための造波水路実験を行った.実験では,水理条件がほぼ同一で,上方より降らせる堆積物供給の速度のみを3段階に変化させることでその影響を調べた.堆積物供給速度が比較的小さい実験では,ウェーブリップルの形状は維持されたまま積み重なっていた.堆積物供給速度が大きくなるにつれてウェーブリップルは平坦化され,その領域は広くなった.今回の実験の水理条件および堆積物の条件(水深:0.3 m,波の周期:1.0 s,波の平均波高:76-78 mm,堆積物粒径:0.20 mm)の下では,砂床上昇速度が32 mm/min以上の実験でウェーブリップルの平坦化が観察された.今回の実験は,ウェーブリップル形状は堆積物供給の影響を受けないというこれまでのウェーブリップル葉理形成モデルにおける仮定が,堆積物供給速度が大きい場合には必ずしも成り立たないことを示唆している.

Flume

Wave flume

10.4096/jssj.80.3

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Citations (0)

Roundness of ripple crest and its implication for sedimentary process

Journal of the Sedimentological Society of Japan (2018)

Naofumi Yamaguchi

Crest

Roundness (object)

Ripple marks

10.4096/jssj.77.29

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Effects of tsunami magnitude and terrestrial topography on sedimentary processes and distribution of tsunami deposits in flume experiments

Sedimentary Geology (2015)

Naofumi Yamaguchi Tomohiro Sekiguchi

Flume

Hydraulic jump

10.1016/j.sedgeo.2015.08.008

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Citations (21)

Ground-penetrating radar profile of the Tottori coastal dunes

The Quaternary Research (Daiyonki-Kenkyu) (2010)

Toru Tamura Yoshinori Kodama Yu Saitoh Kazuaki Watanabe Naofumi Yamaguchi

日本海側を中心に発達する日本列島の完新世海岸砂丘の層序は，砂丘の非活動期に形成されたと考えられるクロスナ層を鍵に，各地の間で対比され，過去の気候変動や人間活動の影響が指摘されてきた．しかし，露頭調査と，遺物やクロスナ層の年代に頼る手法の限界から，1980年代以降，大きな研究の進展は認められなかった．鳥取砂丘において地中レーダ探査を行ったところ，最大25 mの深度まで砂丘堆積物の内部構造が明らかになった．探査断面では，砂丘堆積物のフォーセット層理や海浜堆積物の層理，再活動面，侵食面，フォーセット基底面のユニット境界，古砂丘を覆うローム層，および地下水面が認められた．これらの内部構造は，おもに北西～北北西よりの秋～冬季の卓越風による砂丘の移動と堆積を明らかにしている．地中レーダ断面で明らかになる層序と年代測定との組み合わせにより，日本各地の海岸砂丘の詳細な発達過程が明らかになる見込みがある．

Ground-Penetrating Radar

10.4116/jaqua.49.357

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Citations (2)

Characteristics of ripple patterns formed under shoaling waves

Annual Meeting of the Geological Society of Japan (2007)

Naofumi Yamaguchi Tomohiro Sekiguchi Hideo Sekiguchi

Shoaling and schooling

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DEVELOPMENT OF VENTILATION SYSTEM FOR A HOLD CARRYING REEFER CONTAINERS

Journal of the Kansai Society of Naval Architects (1986)

Akira Masumoto M Nishimura Naofumi Yamaguchi

Development of a mechanical ventilation system for a hold carrying air-cooled type reefer container is described. Before actual design and installation, a model test was carried out to ensure that the system would work properly. After delivery of the ship to the owners, an experimental on board test was also carried out. Testing showed that the system worked successfully, and all reefer containers maintained normal operation.

On board

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Large bedform generated by the 2011 Tohoku-oki tsunami at Kesennuma Bay, Japan

Marine Geology (2012)

Tsuyoshi Haraguchi Kazuhisa Goto Masataka Sato Yuichi Yoshinaga Naofumi Yamaguchi

Tsunami wave

Seabed

Bedform

10.1016/j.margeo.2012.11.005

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