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Journal of Korean Society of Coastal and Ocean Engineers > Volume 31(6); 2019 > Article
J Korean Soc Coast Ocean Eng 2019;31(6): 434-449. doi: https://doi.org/10.9765/KSCOE.2019.31.6.434
해역별 최적 해빈 안정화 공법 선정 Platform 개발을 위한 기초연구 III - 단위 관측 기간에 발생하는 불규칙 파랑과 구속모드의 외중력파, 경계층 Streaming이 횡단표사에 미치는 영향을 중심으로
장병상, 조용준
서울시립대학교 토목공학과
Preliminary Study on the Development of a Platform for the Optimization of Beach Stabilization Measures Against Beach Erosion III - Centering on the Effects of Random Waves Occurring During the Unit Observation Period, and Infra-Gravity Waves of Bound Mode, and Boundary Layer Streaming on the Sediment Transport
Pyong Sang Chang, Yong Jun Cho
Department of Civil Engineering, University of Seoul 163 Seoulsiripdaero, Dongdaemun-gu, Seoul 02504 Korea
Corresponding author: Yong Jun Cho ,Tel: +82-2-6490-2427, Fax: +82-2-6490-2424, Email: youn@uos.ac.kr)
Received: November 4, 2019;  Revised: December 13, 2019.  Accepted: December 23, 2019.
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ABSTRACT
In this study, we develop a new cross-shore sediment module which takes the effect of infra-gravity waves of bound mode, and boundary layer streaming on the sediment transport into account besides the wellknown asymmetry and under-tow. In doing so, the effect of individual random waves occurring during the unit observation period of 1 hr on sediment transport is also fully taken into account. To demonstrate how the individual random waves would affect the sediment transport, we numerically simulate the non-linear shoaling process of random wavers over the beach of uniform slope. Numerical results show that with the consistent frequency Boussinesq Eq. the application of which is lately extended to surf zone, we could simulate the saw-tooth profile observed without exception over the surf zone, infra-gravity waves of bound mode, and boundary-layer streaming accurately enough. It is also shown that when yearly highest random waves are modeled by the equivalent nonlinear uniform waves, the maximum cross-shore transport rate well exceeds the one where the randomness is fully taken into account as much as three times. Besides, in order to optimize the free parameter K involved in the longshore sediment module, we carry out the numerical simulation to trace the yearly shoreline change of Mang-Bang beach from 2017.4.26 to 2018.4.20 as well, and proceeds to optimize the K by comparing the traced shoreline change with the measured one. Numerical results show that the optimized K for Mang-Bang beach would be 0.17. With K = 0.17, via yearly grand circulation process comprising severe erosion by consecutively occurring yearly highest waves at the end of October, and gradual recovery over the winter and spring by swell, the advance of shore-line at the northern and southern ends of Mang-Bang beach by 18 m, and the retreat of shore-line by 2.4 m at the middle of Mang-Bang beach can be successfully duplicated in the numerical simulation.
Keywords: cross-shore sediment, infra-gravity waves of bound mode, boundary layer streaming, shore-line model, individual random waves
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