Experiments are performed in a wave flume to demonstrate the Bragg reflection of linear gravity waves by artificialbars. Three different artificial bars with rectangular, triangular and rectified cosinoidal shapes are...Experiments are performed in a wave flume to demonstrate the Bragg reflection of linear gravity waves by artificialbars. Three different artificial bars with rectangular, triangular and rectified cosinoidal shapes are placed discretely on theseabed for measurement of the Bragg reflection. A series of experimental conditions including the number of bars, the pe-riodic bar spacing, the water depth and various wave conditions are tested. Key parameters influencing the Bragg reso-nances are investigated. The experimental data are compared with the values from both theoretical and numerical models.Some key parameters have proved to be effective in describing the primary resonances. Predictive equations of the charac-teristics for the Bragg reflection are proposed in this paper.展开更多
A numerical model, Evolution Equation of Mild-Slope Equation (EEMSE) developed by Hsu et al. (2003), was applied to study the Bragg reflection of water waves over a series of rectangular seabed. Three key parameters o...A numerical model, Evolution Equation of Mild-Slope Equation (EEMSE) developed by Hsu et al. (2003), was applied to study the Bragg reflection of water waves over a series of rectangular seabed. Three key parameters of the Bragg reflection including the peak coefficient of primary Bragg reflection, its corresponding relative wavelength, and the bandwidth, have shown to be effective in describing the characteristics of the primary Bragg reflection. The characteristics of the Bragg reflection were investigated under the various conditions comprising number, height, and spacing interval of a series of rectangular seabed. The results reveal that the peak of Bragg reflection increases with the increase of rectangular seabed height and number, the bandwidth and the shift value of the Bragg reflection depend on the increase of the rectangular seabed height as well as the decrease of rectangular seabed number, and the relative rectangular seabed spacing in the rang of 3 and 4 could produce higher Bragg reflection. Finally, a correlative and regressive analysis is performed by use of the calculated data. Based on the results of the analysis, empirical equations were established. Our study results can provide an appropriate choice of a series of rectangular seabed field for a practical design.展开更多
The purpose of this paper is to develop a functional method for designing a series of submerged breakwaters on practical topography. The method is used to verify the feasibility and effectiveness of Bragg breakwaters ...The purpose of this paper is to develop a functional method for designing a series of submerged breakwaters on practical topography. The method is used to verify the feasibility and effectiveness of Bragg breakwaters for coastal protection by using field topography. The first part of this paper provides definitions and procedures needed in the design process for applying the mechanism of Bragg reflection. Next, Bragg breakwaters are designed on the basis of the cross-sectional topography and then on the plane topography of the Mi-Tuo coast by following the proposed process and procedure. Numerical modeling (Hsu et al., 2003; Wen and Tsai, 2008) was used as a design and assessment tool. Finally, the effectiveness and feasibility of a Bragg breakwater was assessed by practical cases. Based on the mechanism of Bragg reflection, an optimum layout for a series of submerged breakwaters is proposed to protect the Mi-Tuo coast. The results indicate that the proper layout of a series of submerged creakwaters can achieve the objective of beach protection.展开更多
基金by the National Science Council of Taiwan under the contract number of NSC87-2611-E-006-019
文摘Experiments are performed in a wave flume to demonstrate the Bragg reflection of linear gravity waves by artificialbars. Three different artificial bars with rectangular, triangular and rectified cosinoidal shapes are placed discretely on theseabed for measurement of the Bragg reflection. A series of experimental conditions including the number of bars, the pe-riodic bar spacing, the water depth and various wave conditions are tested. Key parameters influencing the Bragg reso-nances are investigated. The experimental data are compared with the values from both theoretical and numerical models.Some key parameters have proved to be effective in describing the primary resonances. Predictive equations of the charac-teristics for the Bragg reflection are proposed in this paper.
基金This researchis supported by the Science Council of Taiwan (Grant No. NSC94-2611-E-172-001)
文摘A numerical model, Evolution Equation of Mild-Slope Equation (EEMSE) developed by Hsu et al. (2003), was applied to study the Bragg reflection of water waves over a series of rectangular seabed. Three key parameters of the Bragg reflection including the peak coefficient of primary Bragg reflection, its corresponding relative wavelength, and the bandwidth, have shown to be effective in describing the characteristics of the primary Bragg reflection. The characteristics of the Bragg reflection were investigated under the various conditions comprising number, height, and spacing interval of a series of rectangular seabed. The results reveal that the peak of Bragg reflection increases with the increase of rectangular seabed height and number, the bandwidth and the shift value of the Bragg reflection depend on the increase of the rectangular seabed height as well as the decrease of rectangular seabed number, and the relative rectangular seabed spacing in the rang of 3 and 4 could produce higher Bragg reflection. Finally, a correlative and regressive analysis is performed by use of the calculated data. Based on the results of the analysis, empirical equations were established. Our study results can provide an appropriate choice of a series of rectangular seabed field for a practical design.
文摘The purpose of this paper is to develop a functional method for designing a series of submerged breakwaters on practical topography. The method is used to verify the feasibility and effectiveness of Bragg breakwaters for coastal protection by using field topography. The first part of this paper provides definitions and procedures needed in the design process for applying the mechanism of Bragg reflection. Next, Bragg breakwaters are designed on the basis of the cross-sectional topography and then on the plane topography of the Mi-Tuo coast by following the proposed process and procedure. Numerical modeling (Hsu et al., 2003; Wen and Tsai, 2008) was used as a design and assessment tool. Finally, the effectiveness and feasibility of a Bragg breakwater was assessed by practical cases. Based on the mechanism of Bragg reflection, an optimum layout for a series of submerged breakwaters is proposed to protect the Mi-Tuo coast. The results indicate that the proper layout of a series of submerged creakwaters can achieve the objective of beach protection.
