PREDICTION MODELS OF RANDOM WAVE TRANSFORMATION IN SHALLOW WATER

Hajime Mase 한국해안해양공학회 1999 학술강연회 발표논문초록집 Vol.2 No.1

This paper summarizes and explains existing prediction models of random wave transformation in shallow water and a hybrid wave model which consists of a spectral wave model and a probabilistic bore-type energy dissipation model. The hybrid wave model was applied to predict the vertically and horizontally two-dimensional wave transformations in shallow water. The agreement between the various observations by laboratory and field experiments and the predictions by the hybrid wave model was satisfactorily good.

Development of Wave Overtopping–Overflow Transition Model Based on Full-scale Experiments

Hajime Mase,Sooyoul Kim,Makoto Hasegawa,Jae-Hoon Jeong,윤종성 한국해양공학회 2020 韓國海洋工學會誌 Vol.34 No.2

When high waves and storm surge strike simultaneously, the characteristics of the fluid field change drastically from overtopping according to the wave runup height to overflow through a transition state that combines overtopping and overflows. However, an estimation model or evaluation method has not yet been established because there is not enough engineering data. This study developed a wave overtopping-overflow transition model based on a full-scale experiment involving wave overtopping and overflow transition, which appropriately reproduced the effect of waves or the temporal change in inundation flow. Using this model to perform a calculation for the wave overtopping and overflow transition process under typical circumstances, this study determined the wave runup height and features of the inundation flow under time series changes as an example.

딥러닝을 이용한 장기 파랑예측 가능성 연구

Tracey H.A. Tom,Hajime Mase,Makoto Hasegawa,정재훈(Jae-Hoon Jeong),윤종성(Jong-Sung Yoon),김연중(Yeon-Joong Kim) 한국연안방재학회 2020 한국연안방재학회지 Vol.7 No.4

Numerical wave prediction models require a large amount of computational power to timely complete the required calculations. Artificial Neural Networks (ANN) have been introduced to perform predictions at a lesser computational cost and increased processing speed. Deep learning and specifically Convolutional Neural Networks (CNN) have become accepted for various image recognition applications. Motivation for the examination of wave prediction by deep learning came from the success of CNN in vision applications and the similarity of meteorological weather grid data to visual images. This study investigates a deep learning technique using the Japan Meteorological Agency’s Grid Point Value Mesoscale Model to predict wave height and period. In particular, this study uses the Xception deep learning architecture with depthwise separable convolution to obtain improved wave height and period prediction over artificial neural networks, and gets overall success results.

Assessment of long-term impact of storm surges around the Korean Peninsula based on a large ensemble of climate projections

Yang, Jung-A.,Kim, Sooyoul,Mori, Nobuhito,Mase, Hajime Elsevier 2018 Coastal engineering Vol.142 No.-

<P><B>Abstract</B></P> <P>This study assesses the long-term impact of storm surges due to typhoons around the Korean Peninsula (KP) resulting from climate change. Long-term projection is conducted based on the large ensemble experiments on so-called d4PDF for the past and +4 K future climate conditions over 5000 years by a single atmospheric global climate model developed by the Meteorological Research Institute of Japan. The use of a large ensemble is to enable one to obtain probabilistic future changes in low-frequency of extreme storm surge events. The properties of typhoons which may directly and indirectly have an effect on the KP in terms of past and future climate conditions is extracted from d4PDF. These are employed as the driving force in the projection of future storm surges around the KP. The storm surge heights (SSH) around the KP are projected to increase in the future climate except for around some areas in the south coast. The magnitude of future change of SSH varies spatially. The maximum variation was estimated to be 0.36 m (9.9%) with a 100-year return period in the west area of the southeastern coast of the KP. The locations of the areas vulnerable to storm surge shift to the north area of the western region and to the west area of the southern regions in the Korean Peninsula under the future climate. The characteristic of future change to areas where high SSHs will occur coincides with that of the typhoon tracks.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The SSH are projected to increase under the future climate except for some areas in the south coast of the KP. </LI> <LI> The maximum variation was estimated to 9.9 % with the 100-year return period in the west area of the southeastern coast. </LI> <LI> The vulnerable locations to future surge shift to the north in the western region and to the east in the southern region. </LI> <LI> The characteristic of future change of the vulnerable locations to storm surge coincides with one to typhoon track. </LI> </UL> </P>

A hydrodynamic model of nearshore waves and wave-induced currents

Ahmed Khaled Seif,Masamitsu Kuroiwa,Mazen Abualtayef,Hajime Mase,Yuhei Matsubara 대한조선학회 2011 International Journal of Naval Architecture and Oc Vol.3 No.3

In This study develops a quasi-three dimensional numerical model of wave driven coastal currents with accounting the effects of the wave-current interaction and the surface rollers. In the wave model, the current effects on wave breaking and energy dissipation are taken into account as well as the wave diffraction effect. The surface roller associated with wave breaking was modeled based on a modification of the equations by Dally and Brown (1995) and Larson and Kraus (2002). Furthermore, the quasi-three dimensional model, which based on Navier-Stokes equations, was modified in association with the surface roller effect, and solved using frictional step method. The model was validated by data sets obtained during experiments on the Large Scale Sediment Transport Facility (LSTF) basin and the Hazaki Oceanographical Research Station (HORS). Then,a model test against detached breakwater was carried out to investigate the performance of the model around coastal structures. Finally, the model was applied to Akasaki port to verify the hydrodynamics around coastal structures. Good agreements between computations and measurements were obtained with regard to the cross-shore variation in waves and currents in nearshore and surf zone.

A hydrodynamic model of nearshore waves and wave-induced currents

Sief, Ahmed Khaled,Kuroiwa, Masamitsu,Abualtayef, Mazen,Mase, Hajime,Matsubara, Yuhei The Society of Naval Architects of Korea 2011 International Journal of Naval Architecture and Oc Vol.3 No.3

In This study develops a quasi-three dimensional numerical model of wave driven coastal currents with accounting the effects of the wave-current interaction and the surface rollers. In the wave model, the current effects on wave breaking and energy dissipation are taken into account as well as the wave diffraction effect. The surface roller associated with wave breaking was modeled based on a modification of the equations by Dally and Brown (1995) and Larson and Kraus (2002). Furthermore, the quasi-three dimensional model, which based on Navier-Stokes equations, was modified in association with the surface roller effect, and solved using frictional step method. The model was validated by data sets obtained during experiments on the Large Scale Sediment Transport Facility (LSTF) basin and the Hazaki Oceanographical Research Station (HORS). Then, a model test against detached breakwater was carried out to investigate the performance of the model around coastal structures. Finally, the model was applied to Akasaki port to verify the hydrodynamics around coastal structures. Good agreements between computations and measurements were obtained with regard to the cross-shore variation in waves and currents in nearshore and surf zone.

Effect of Climate Change on Performance-Based Design of Caisson Breakwaters

Suh, Kyung-Duck,Kim, Seung-Woo,Mori, Nobuhito,Mase, Hajime American Society of Civil Engineers 2012 Journal of waterway, port, coastal, and ocean engi Vol.138 No.3