Characteristic of Wave Diffraction and Reflection for Irregular Waves in SWASH Model Around Small Port Structures

摘要

The numerical model of Boussinesq approximation,which is mainly used for evaluating the port calmness due to the irregular waves,has a limit of applicability of lattice size in ports such as marinas with narrow port openings of around 30 m.The SWASH model controls the partial reflection according to the depth,porosity coefficient and structure size when applying the reflected wave incident on the structure and terrain.In this study,the partial reflection evaluation at the front of the structure according to the bottom shape and the shape of the structure are examined.In order to evaluate the reproducibility of the model due to the diffraction waves entering the term,the area of incidence at right angles and inclination of the structure is constructed and compared with the diffraction theory suggested by Goda et al.(1978).The experimental results of the sectional structure reflectances calculated as the depth mean show reflectances similar to the approximate values of the reflectances presented by Stelling and Ahrens (1981).It is considered that the reflected wave is well reproduced according to the control of the reflected wave at the boundary and the shape and topography of the structure.Compared with previous studies to examine the diffraction of the wave incident from the breakwater opening,the wave incidence angle and the shape of the diffraction wave are very similar to the theoretical values,but both oblique and rectangular incidence In the case where the direction concentration is small,the diffraction degree is underestimated in some sections with the crest ratio of 0.5 to 0.6.