23. Intra-wave-phase cross-shore profile modelling by using boundary-fitted slowly moving grid

Hyoseob Kim1, Seung-Won Baek2, Dae-hee Hwang3, Kyoung-Pil Lee4, Jae-Youll Jin5, Chang-Hwan Jang6

1, 2, 3, 4Department of Civil and Environment Engineering, Kookmin University, Seoul, Korea

5Korea Institute of Ocean Science and Technology, Gyeonggi-do, Korea

6Korean Intellectual Property Office, Daejeon, Korea

1Corresponding author

E-mail: 1hkim@kookmin.ac.kr, 2akfls7266@naver.com, 3bigmac38@nate.com, 488snowman@naver.com, 5jyjin@kiost.ac.kr, 6cjang@kipo.go.kr

Received 14 November 2015; received in revised form 30 April 2016; accepted 21 September 2016

DOI https://doi.org/10.21595/mme.2016.16641

Abstract. Coastal bed profile change is described by bed load, pick-up, and settling on a boundary-fitted moving grid. Existing bed load formula is modified by changing threshold bed shear stress to reflect local bed slope. A numerical model system adopting the above function is developed to simulate cross-shore sediment transport around swash zone with steep bed slope as well as surf zone. The model system adopts a moving boundary grid which fits bed boundary slope, and other horizontal grid lines are parallel to the bed grid line. The model system is composed of flow module and sediment transport module. The flow module solves continuity equation and Reynolds-average Navier-Stokes momentum equations in intra-wave-phase manner. The flow module provides detailed flow information including near-bed fluid velocity which varies asymmetrically within a regular wave period near sea-bed and wave-phase average undertow profile of main fluid body including wave boundary layer. The sediment transport module solves sediment mass conservation equation. Exchange of sediment mass between bed itself and fluid column containing suspended sediment happens through pick-up and deposition. Wild bed level undulation is controlled by using a smoothing method. Model system is applied to two extreme cases of sand experiments by Kajima et al., and reasonable agreements between measurements and computations are obtained for both onshore-dominant and offshore-dominant cases.

Keywords: bed slope, pickup, swash zone, cross-shore, boundary-parallel grid, sediment transport.

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Cite this article

Kim Hyoseob, Baek Seung‑Won, Hwang Dae‑hee, Lee Kyoung‑Pil, Jin Jae‑Youll, Jang Chang‑Hwan Intra‑wave-phase cross‑shore profile modelling by using boundary‑fitted slowly moving grid. Mathematical Models in Engineering, Vol. 2, Issue 2, 2016, p. 78‑93.

 

Mathematical Models in Engineering. December 2016, Volume 2, Issue 2

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