Numerical study of solitary wave propagation in curved channels

金沢大学理工研究域環境デザイン学系A numerical model is developed for the extended Boussinesq equations expressed in the generalized curvilinear coordinate system. The model is applied to the study of solitary wave propagation through circular channels. The general features of solitary wave propagation are described and the effects of channel width and incident wave height on the transmission and reflection properties are examined. It is shown that the wave transformation becomes significant in wide channels. The maximum crest height at the outer wall of channel is then investigated in detail. The maximum crest height can reach almost twice as large as the incident wave amplitude in wide channels. The numerical results indicate that the maximum crest height can be correlated fairy well with a single dimensionless parameter

Determination of semi-empirical models for mean wave overtopping using an evolutionary polynomial paradigm

The present work employs the so-called Evolutionary Polynomial Regression (EPR) algorithm to build up a formula for the assessment of mean wave overtopping discharge for smooth sea dikes and vertical walls. EPR is a data-mining tool that combines and integrates numerical regression and genetic programming. This technique is here employed to dig into the relationship between the mean discharge and main hydraulic and structural parameters that characterize the problem under study. The parameters are chosen based on the existing and most used semi-empirical formulas for wave overtopping assessment. Besides the structural freeboard or local wave height, the unified models highlight the importance of local water depth and wave period in combination with foreshore slope and dike slope on the overtopping phenomena, which are combined in a unique parameter that is defined either as equivalent or imaginary slope. The obtained models aim to represent a trade-off between accuracy and parsimony. The final formula is simple but can be employed for a preliminary assessment of overtopping rates, covering the full range of dike slopes, from mild to vertical walls, and of water depths from the shoreline to deep water, including structures with emergent toes.This research was funded by European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No.: 792370.Peer ReviewedPostprint (published version

Development of Real Time Storm Surge Forecasting Using Artificial Neural Network

Information Management and Decision Support System

Development of 3D Morphodynamic Model Considering Wave-current Interaction

This study develops a three dimensional morphodynamic model around coastal structures considering a wave-current interaction. In the wave model, the current effects on wave breaking and energy dissipation are taken into account as well as the wave diffraction effect. Firstly, an experimental data set from the Large Scale Sediment Transport Facility was used to evaluate the predictive capability of the model. Secondly, several model tests against detached breakwaters were carried out to investigate the performance of the model. Finally, the model was applied to Kunnui fishing port for the prediction of the bathymetry after 1 year, and for the calibration and verification of the morphodynamics around the coastal structures. For the model tests, the performance of the model was investigated; and for Kunnui fishing port, the model result shows a good agreement with the field observation. It was found that the wave

Artificial neural network-based storm surge forecast model: Practical application to Sakai Minato, Japan

The present study describes a novel way of a systematic and objective selection procedure for the development of an Artificial Neural Network-based storm Surge Forecast Model (ANN-SFM) with the 5, 12 and 24 h-lead times and its application to Sakai Minato area on the Tottori coast, Japan. The selection procedure guides how to determine the superiority of the best performing model in terms of the appropriate combination of unit number in the hidden layer and parameter in the input layer. In the application of ANN-SFM to Sakai Minato, it is found that the best 5 and 12 h-forecast ANN-SFMs are established with the most suitable set of 70 units (the number of hidden neurons) and the input components of surge level, sea level pressure, the depression rate of sea level pressure, longitude, latitude, central atmospheric pressure and highest wind speed. The best 24 h-forecast ANN-SFM is determined with 160 units and the input parameters of surge level, sea level pressure, the depression rate of sea level pressure, longitude and latitude. The proposed method of the selection procedure is able to be adaptable to other coastal locations for the development of the artificial neural network-based storm surge forecast model as establishing the superiority of the most relevant set combining unit numbers and input parameters

Analysis of Climate Change Effects on Seawall Reliability

Crown heights of seawalls should be designed to suppress overtopping discharge to a permissible level. The permissible level is determined from viewpoints of the structure types of coastal seawalls and hinterland use. It is usually difficult to design the crown heights of seawalls, especially in the present time where climate change due to global warming is expected. This study analyzes climate change effects such as sea level rise (SLR) and increase of waves and surges on the failure probability of seawalls under various conditions of crown height, toe depth and slope by using a Level III reliability analysis. It was found that the difference of SLR trends (fast, medium or low) has less impact on overtopping rates than the differences in wave height change for a seawall at a target location

A coastal area model considering wave-current interaction and its application to wide-crested submerged breakwater

This study is concerned with development of a 3D morphodynamic predictive model for considering wave-current interaction by using wave action balance equation. The developed model was applied to model tests associated with a detached breakwater and wide-crested submerged breakwaters, and the influences of strong currents around the structures into wave height distribution and bathymetry change were investigated. Furthermore, the morphodynamics around the artificial reefs in the Uradome Beach, Tottori, Japan, was computed. From the computed results, a large scour hole due to strong rip-currents in the opening of the reefs was reproduced. The applicability of the model was confirmed

Development and verification of wall-flap-gate as tsunami inundation defence for nuclear plants

A wall-flap-gate is automatic watertight door, and it works by buoyancy without powered machineries and human operations. In the Tohoku Earthquake tsunamis, serious damages were caused by inundation from ventilators of outer walls in power plants. The wall-flap-gate is estimated to be effective in keeping sustainability of nuclear plants against extreme tsunamis. The present study examines the hydrodynamic characteristics of the wall-flap-gate by hydraulic model experiments and verifies its capability of flood prevention for nuclear plants through various prototype tests. The experimental results proved that the wall-flap-gate had sufficient strength, watertightness, and durability against tsunamis and that its motion was not disturbed by debris. The viability of the wall-flap-gate as an inundation defence structure for nuclear plants was confirmed through this study. As a result, practical wall-flap-gates are installing on Hamaoka nuclear power station in Shizuoka prefecture, Japan

Microwave Imaging Reflectometry Experiment in TPE-RX

Microwave imaging reflectometry (MIR) was developed in TPE-RX, one of the world’s largest reversed field pinch (RFP) devices. The system optics are made of aluminum mirrors, Teflon lenses, and Plexiglas plates in order to reduce size. In this system, frequencies are stabilized so that noise can be reduced using narrow bandpass filters. A 4×4 2-D mixer array and phase detection system have also been developed. With this system, density fluctuations in the high-Θ RFP plasma, pulsed poloidal current drive (PPCD) plasma, and quasi-single helicity(QSH) plasma are observed in TPE-RX. This is the first MIR experiment in an RFP device