• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.90-90
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• 2019

본 연구에서는 SWASH(Simulating WAves till SHore) 모형의 염분분포 해석의 정확성을 평가하기 위해 Goswami et al.(2007)의 모형실험을 재현하였다. SWASH모형은 Delft 대학에서 개발된 비정수압수치모형으로 연직방향으로 층(layer)을 나누어 자유수면변위를 정확하게 예측하고 표준 ${\kappa}-{\varepsilon}$ 난류모델을 이용해 염분, 온도 및 침전물 등의 난류확산을 계산한다. 우선 Goswami et al.(2007)의 모형실험 중 정상상태의 모형실험을 이용해 층수에 따른 수치모형의 정확도를 평가하였다. SWASH 모형의 층수를 늘리며 수치모의를 수행한 결과, 층수가 늘어날수록 종, 횡 방향의 염분농도 분포가 정확하게 나타나는 것을 확인하였다. 추가로 SWASH 수치모형을 이용해 염수침투 및 후퇴 상태의 모형실험도 수치모의하였다. 염수의 공급에 따라 시간에 따른 염분농도 분포가 변화하는 것을 확인하였다. 또한 연직방향의 층수가 많은 경우 모형실험의 결과와 비교적 잘 일치하는 것을 확인할 수 있다. 따라서 연직방향의 층수를 늘려감에 따라 수심방향으로 더 정밀한 염분분포 해석이 가능하다는 것을 알 수 있다. 그러나 연직방향으로 많은 층을 나눈 경우 계산시간이 증가하기 때문에 수심이 작거나 연직방향의 염분농도 분포가 중요하지 않은 경우라면 적절한 층수(5~10 layer)를 고려해 수치모의를 수행하는 것이 시간과 비용측면에서 더욱 경제적이라고 할 수 있다.

• Journal of Korea Water Resources Association
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• v.56 no.10
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• pp.603-617
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• 2023

This study aims to provide a better understanding of the turbulent flow characteristics in swash zone. A double dam-break method is employed to generate the swash zone flow. Comparing with the conventional single dam-break method, a delay between two gate opening can be controlled to reproduce various interactions between uprush and backwash. For numerical simulations, overInterDyMFoam based on OpenFOAM is adopted. Using overInterDyMFoam, interface between two immiscible fluids having different densities (i.e., air and water phases) can be tracked in a moving mesh with multiple layers. Two-dimensional Reynolds-Averaged Navier-Stokes equations are solved with a standard 𝜅-𝜖 turbulence model for momentum and continuity. Numerical model results are validated with laboratory experiment data for the time series of water depth and streamwise velocity. Turbulent kinetic energy distribution is further investigated to identify the turbulence evolution for each flow regime (i.e., uprush, backwash, and swash-swash interaction).

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.4
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• pp.169-179
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• 2017

In this study, we applied the wave generation method by relaxation method to the SWASH model, which is a non - hydrostatic numerical model, for stable and accurate wave generation of linear and nonlinear waves. To validate the relaxation wave generation method, we were simulated various wave, including the linear wave and nonliner wave and compared with analytical solution. As a result, the incident wave was successfully generated and propagated in all cases from Stokes waves to cnoidal wave. Also, we were confirmed that the wave height and the waveform were in good agreement with the analytical solution.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.5
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• pp.591-598
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• 2015

A hydraulic characteristics in the surf zone such as wave breaking points, wave set-down, wave set-up, wave-induced currents and run-up heights are studied using the SWASH model during Typhoon NAKRI(1412) in Haeundae Beach. Incident wave conditions is obtained from one-hourly observed wave data by KHOA and irregular wave by JONSWAP spectrum is given as an open boundary condition in the model. A Wave-induced current patterns by the SWASH model is compared with the observed currents and sediment flux patterns in that areas, the calculated maximum wave run-up heights in the model is compared with the video monitoring data, the empirical formula by Stockdon et al. and Mase. A dominant longshore currents toward the east of the beach appears due to the effect of incident wave direction and the geographical features and some rip currents occurs at the central part of the beach. The maximum wave run-up height(1.15 m) by the SWASH model shows a similar pattern with the video monitoring data(1.26 m) and the magnitude shows a similar result(1.33m) by Stockdon et al.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.3
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• pp.114-122
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• 2018

This paper introduces a non-hydrostatic wave model SWASH for simulating wave interactions with porous structures. This model calculates the flow in porous media based on volume-averaged Reynolds-averaged Navier-Stokes equations (VARANS) in ${\sigma}$-coordinate. The empirical coefficients of resistance used to account for the flow in a porous media often need to be measured or calibrated. In this study, the empirical resistance coefficients used in the model are calibrated and validated using laboratory experiments, involving dam-break flow through porous media, and solitary wave interactions with a porous structure. It is shown that the agreement between experimental and numerical results is generally satisfactory. It is also confirmed that non-hydrodynamic model, SWASH, is computationally much more efficient than the three-dimensional porous flow models based on VOF approach.

• Journal of Korea Water Resources Association
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• v.35 no.1
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• pp.13-24
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• 2002

In a physically realistic but simplified manner, an attempt is made in this study to develop a predictive model for swash hydrodynamics across the shore due to the storm waves on an arbitrary beach profile. Date from the SUPERTANK laboratory Data Collection Project are used for the model development, in which experiments were designed to simulate dune erosion under storm conditions at a prototype scale. The model predicts variations of swash height, velocity and period across the beach face in a swash zone. In general, the model proves to be capable of predicting variations of swash height, velocity and period across the shore. Quantitatively better predictions for the swash parameters could be achieved by improving the prediction of the beach face elevation, ymax, where the significant swash height becomes zero.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.6
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• pp.382-390
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• 2015

To simulate a complicated hydrodynamic phenomena in the surf zone, the SWASH model is used in Haeundae Beach. The SWASH model is well known as a model competing with the Boussinesq-type model in terms of near shore waves and wave-induced currents modelling. This study is aimed to the detailed analysis of seasonal waves and wave-induced current simulation in Haeundae Beach, where the representative seasonal wave conditions was obtained from hourly measured wave data in 2014 by Korea Hydrographic and Oceanographic Administration( KHOA). Incident wave conditions were given as irregular waves by JONSWAP spectrum. The calculated seasonal wave-induced current patterns were compared with the field observation data. In summer season, a dominant longshore current toward the east of the beach appears due to the effect of incident waves from the South and the bottom bathymetry, then some rip currents occurs at the central part of the beach. In the winter season, ESE incident waves generates a strong westward longshore currents. However, a weak eastward longshore currents appears at the restricted east side areas of the beach.

• Water for future
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• v.56 no.9
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• pp.72-76
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• 2023

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1B
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• pp.95-109
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• 2008

We numerically analyzed the nonlinear shoaling, a plunging breaker and its accompanying energetic suspension of sediment at a bed, and a redistribution of suspended sediments by a down rush of preceding waves and the following plunger using SPH with a Gaussian kernel function, Lagrangian Dynamic Smagorinsky model (LDS), Van Rijn's pick up function. In that process, we came to the conclusion that the conventional model for the tractive force at a bottom like a quadratic law can not accurately describe the rapidly accelerating flow over a swash zone, and propose new methodology to accurately estimate the bottom tractive force. Using newly proposed wave model in this study, we can successfully duplicate severely deformed water surface profile, free falling water particles, a queuing splash after the landing of water particles on the free surface and a wave finger due to the structured vortex on a rear side of wave crest (Narayanaswamy and Dalrymple, 2002), a circulation of suspended sediments over a swash zone, net transfer of sediments clouds suspended over a swash zone toward the offshore, which so far have been regarded very difficult features to mimic in the computational fluid mechanics.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.468-477
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• 2019

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 30m. 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.