Wave-induced Currents Research Articles

Nearshore Current Pattern and Rip Current Occurrence at Jungmun Beach, Jeju by Numerical Computation

A nearshore current or a wave-induced current is an important phenomenon in a nearshore zone, which is composed of longshore, cross-shore, and rip currents. The nearshore current is closely related to the occurrence of coastal accidents by beachgoers. A considerable number of coastal accidents by beachgoers involving the rip current have been reported at Jungmun Beach. However, in studies and observations of the nearshore current of Jungmun Beach, understanding of the rip current pattern remains unclear. In this study, a scientific approach is taken to understand the nearshore current and the rip current patterns at Jungmun Beach by numerical computation for year of 2015. From results of numerical computation, the occurrence and spatial characteristics of the rip current, and the similarities between the rip current and incident wave conditions are analyzed. The primary results of this study reveal that the rip currents are frequently generated at Jungmun Beach, especially in the western parts of the beach, and that the rip currents often occur with a wave breaking height of around 0.5 ~ 0.7 m, a wave period of around 6 ~ 8 seconds, and a breaking angle of around 0 ~ 15 degrees.

Factors responsible for the limited inland extent of sand deposits on Leyte Island during 2013 Typhoon Haiyan

AbstractPrevious geological studies suggest that the maximum inland extent of storm‐induced sand deposits is shorter, but their thickness is larger, than those of tsunami‐induced sand deposits. However, factors that determine the maximum extent and thickness of storm deposits are still uncertain. We conducted numerical simulations of storm surge, waves, and sediment transport during Typhoon Haiyan in order to understand the distribution and sedimentary processes responsible for storm deposits. Numerical results showed that wave‐induced currents slightly offshore were strong, but attenuated rapidly in the inland direction after wave breaking. Therefore, sediments were not transported far inland by waves and storm surge. Consequently, the maximum inland extent of storm deposits was remarkably shorter than the inland extent of inundation. We also revealed that vegetation (roughness coefficient) and typhoon intensity greatly affect the calculation of maximum extent and thickness distribution of storm deposits. As the duration of wave impact on a coast is relatively long during a storm (hours, compared to minutes for a tsunami), sediments are repeatedly supplied by multiple waves. Therefore, storm deposits tend to be thicker than tsunami deposits, and multiple layers can form in the internal sedimentary structure of the deposits. We infer that limitation of the sand deposit to within only a short distance inland from the shoreline and multiple layers found in a deposit can be used as appropriate identification proxies for storm deposits.

Analysis of Wave and Current in Anmok Coastal Waters

In this study, waves and currents observed by acoustic AWAC, VECTOR and Aquadopp Profiler in Anmok coastal waters were analysed to account for the variability of wave and current and to understand the mechanism of sediment transport generated by wave-induced current in the surf-zone. The monthly variation of wave and residual currents were analysed and processed with long-term observed AWAC data at station W1, located at the water depth of about 18m measured during from February 2015 to September 2016. Wave-induced currents were also analysed with intensive field measurements such as wave, current, suspended sediment, and bathymetry data observed at the surf-zone during in winter and summer. The statistical result of wave data shows that high waves coming from NNE and NE in winter (DEC-FEB) are dominant due to strong winds from NE. But in the other season waves coming from NE and ENE are prevalent due to the seasonal winds from E and SE. The residual currents with southeastern direction parallel to the shoreline are dominant throughout a year except in winter showing in opposite direction. The speed of ebb-dominant southeastern residual currents decreasing from surface to the bottom is strong in summer and fall but weak in winter and spring. By analysing wave-induced current, we found that cross-shore current were generated by swell waves mainly in winter with incoming wave direction about 45° normal to the shoreline. Depending on the direction of incoming waves, longshore currents in the surf-zone were separated to southeastern and northwestern flows in winter and summer respectively. The variation of observed currents near crescentic bars in the surf-zone shows different direction of longshore and cross-shore currents depending on incoming waves implying to the reason of beach erosion generating the beach cusp and sandbar migration during high waves at Anmok.

Vertically varying Eulerian mean currents induced by internal coastal Kelvin waves

The lost momentum in spatially damped internal Kelvin waves reappears as Eulerian mean currents through the action of the nonlinear wave-wave interaction terms. A novel expression is derived for the steady balance between the frictional force on the coastally trapped horizontal Eulerian mean flow, and the forcing from the wave field in terms of the mean wave Reynolds stresses and the horizontal divergence of the Stokes drift. The forcing can be expressed in terms of orthogonal eigenfunctions for internal waves, yielding the vertical variation of the Eulerian mean flow. For arbitrary values of the Brunt-Vaisala frequency N, it is shown that the wave forcing on the Eulerian mean is always negative, yielding a Poiseuille type flow. Therefore, unlike the Stokes drift velocity in internal Kelvin waves which exhibits a backward drift for the first mode in the region of maximum N, the wave-induced horizontal Eulerian mean current is always in the direction of the waves. The results are illustrated by an example from Van Mijenfjorden in Svalbard, which is an arctic sill fjord where internal waves are generated by the action of the barotropic semi-diurnal tide. This article is protected by copyright. All rights reserved.

XBEACH 모형에 의한 해운대 해수욕장 양빈후의 해빈류 특성 변화

In this study, to predict the effect of beach nourishment at Haeundae Beach, the waves and wave-induced currents were compared before and after beach nourishment using the XBEACH model. Representative wave conditions were determined for the data observed during 2014 (KHOA). Then, the Hs,max and Hs,1/10 values, and their prevalent directions, were used in the numerical modeling input data. A variable grid system was used for the <TEX>$5km{\times}2.5km$</TEX> model areas, and irregular waves based on the JONSWAP spectrum were given as incident wave conditions. In the summer season, eastward wave-induced currents were developed along the beach by the incident wave direction. Before the beach nourishment, the maximum speed around the surf zone was 1.2-1.5 m/s in the central zone of the beach, whereas the maximum speed increased to 1.4-1.6 m/s at the same areas when the currents toward Mipo Harbor were blocked as an effect of the groins after the beach nourishment. In the winter season, westward wave-induced currents were developed along the beach by the incident wave direction. After the beach nourishment, the maximum current speed increased slightly around the surf zone in the central area of the beach, and the littoral current speed decreased at the submerged breakwaters located at Dongbaek Island. As a result, after the beach nourishment, the maximum wave-induced currents increased about 10% in the surf zone of the central area of the beach.

Using zircon U–Pb ages to constrain the provenance and transport of heavy minerals within the northwestern shelf of the South China Sea

Numerous ore-grade heavy mineral placer deposits occur in the northern South China Sea region. Previous studies on these deposits have focused on the heavy-mineral ore resources themselves, but the provenance and transport pathways of these heavy minerals are poorly constrained. This paper presents U–Pb ages of detrital zircons from sediments within the northwestern shelf of the South China Sea, and uses this new dataset to determine the provenance and transport pathway of the sediments. Zircons in sediments from ten areas of the northwestern shelf exhibit distinct age populations, suggesting that they have multiple provenances. Zircons in sediments from the Pearl River Mouth, Shangchuan Island, and Moyang River Mouth areas all have an obvious peak of Mesozoic ages, indicating that they have similar sediment provenances; i.e., mainly from the Pearl River, and to a lesser degree from the Moyang River. Zircons in sediments from the areas around the Jian River Mouth and Leizhou Bay, and off Hainan Island have an early Paleozoic age, suggesting that the sediments predominantly originate from the Yunkai massif. Zircons of the sediments from the remaining four areas, the Leiqiong Strait, Wanquan River Mouth, Qiongdongnan, and the Outer Shelf, have Yanshannian and Indosinian age peaks in addition to an obvious early Paleozoic population, implying mixed provenances, including the Yunkai massif and Hainan Island. The sediment transport may have involved two hydrodynamic conditions in two distinct stages. First, the Guangdong Longshore Current carried the river sediments to where they dispersed in the inner shelf; subsequently, wave-induced strong currents further transported sandy sediments southeastward to the outer shelf. In addition to explaining the provenance and transport pathways of heavy minerals within the northwestern shelf of the South China Sea, these results provide new information relevant to exploration for heavy-mineral placer deposits.

Electron cyclotron current drive simulations for finite collisionality plasmas in Wendelstein 7-X using the full linearized collision model

The Electron Cyclotron Current Drive (ECCD) efficiency is usually modeled in the collisionless limit. While such models are sufficient for plasmas with rather low collisionality, they might underestimate the current drive in plasmas at low temperatures likely to occur at the initial phase of high density device operation. In this paper, the impact of finite collisionality effects on the wave-induced current drive is studied for a high-mirror configuration of Wendelstein 7-X using a combination of the drift kinetic equation solver NEO-2 and the ray-tracing code TRAVIS for a realistic set of plasma parameter profiles. The generalized Spitzer function, which describes the ECCD efficiency in phase space, is modeled with help of NEO-2, which uses the full linearized Coulomb collision operator, including energy and momentum conservation. Within this approach, the linearized drift kinetic equation is solved by means of the field line integration technique without any simplifications on device geometry. The results of the ray-tracing code TRAVIS using the ECCD efficiency from NEO-2 within the adjoint approach show a significant difference for the driven current when compared to commonly used collisionless models for the ordinary as well as the extraordinary second harmonic mode.

Development of a depth-integrated longshore current model with unstructured grids

A depth-integrated model for simulating wave-induced longshore current was developed with unstructured grids. Effects of surface roller and horizontal mixing under combined waves and currents were incorporated in the numerical model. Recommended values of model coefficients were also proposed based on sensitivity analysis. Field observations and three series of laboratory measurements including two cases conducted on the plane beach and one implemented on the ideal inlet were employed to examine the predictive capability of this model. For the field case and laboratory cases conducted on the plane beach, numerical results were compared favorably with the measured data. For the case with an ideal inlet, simulated circulation pattern is supposed to be reasonable although some deviations between numerical results and measured data still can be detected.

Air–Sea Interactions in Light of New Understanding of Air–Land Interactions

Abstract Air–sea interactions are investigated using the data from the Coupled Boundary Layers Air–Sea Transfer experiment under low wind (CBLAST-Low) and the Surface Wave Dynamics Experiment (SWADE) over sea and compared with measurements from the 1999 Cooperative Atmosphere–Surface Exchange Study (CASES-99) over land. Based on the concept of the hockey-stick transition (HOST) hypothesis, which emphasizes contributions of large coherent eddies in atmospheric turbulent mixing that are not fully captured by Monin–Obukhov similarity theory, relationships between the atmospheric momentum transfer and the sea surface roughness, and the role of the sea surface temperature (SST) and oceanic waves in the turbulent transfer of atmospheric momentum, heat, and moisture, and variations of drag coefficient Cd(z) over sea and land with wind speed V are studied. In general, the atmospheric turbulence transfers over sea and land are similar except under weak winds and near the sea surface when wave-induced winds and oceanic currents are relevant to wind shear in generating atmospheric turbulence. The transition of the atmospheric momentum transfer between the stable and the near-neutral regimes is different over land and sea owing to the different strength and formation of atmospheric stable stratification. The relationship between the air–sea temperature difference and the turbulent heat transfer over sea is dominated by large air temperature variations compared to the slowly varying SST. Physically, Cd(z) consists of the surface skin drag and the turbulence drag between z and the surface; the increase of the latter with decreasing V leads to the minimum Cd(z), which is observed, but not limited to, over sea.

Numerical simulation of sediment transport in coastal waves and wave-induced currents

Prediction of coastal sediment transport is of particularly importance for analyzing coast erosion accurately and solving the corresponding coast protection engineering problems. The present study provided a numerical scheme for sediment transport in coastal waves and wave-induced currents. In the scheme, the sand transport model was implemented with wave refraction-diffraction model and near-shore current model. Coastal water wave was simulated by using the parabolic mild-slope equation in which wave refraction, diffraction and breaking effects are considered. Wave-induced current was simulated by using the nonlinear shallow water equations in which wave provides radiation stresses for driving current. Then, sediment transport in waves and wave-induced currents was simulated by using the two-dimensional suspended sediment transport equations for suspended sediment and the bed-load transport equation for bed load. The numerical scheme was validated by experiment results from the Large-scale Sediment Transport Facility at the US Army Corps of Engineer Research and Development Center in Vicksburg. The numerical results showed that the present scheme is an effective tool for modeling coastal sediment transport in waves and near-shore currents.

연안침식방지사업의 해양물리분야 평가실태 및 개선방안

This study analysed the documents of Sea Area Utilization Consultation of JongChun and ApHae located in West Coast of Korea and NaJeong located in East Coast of Korea in order to find out problems of site surveys and numerical simulations for coastal erosion projects of ocean physics, and suggested the improvement way to go. Current especially like wave-induced current is the one of the important external forces to handle coastal erosion but underestimated in the west coast. In case of east coast the various tests including wave-induced current were conducted but less efficient to find out the reasons of coastal erosion. The stiffness structure to protect coastal line like beach made the secondary erosion by using them without sufficient analysis for the erosion. In order to consult a Sea Area Utilization Consultation those are needed to review the scenarios for external forces such as wave and tidal currents, the site surveys for external forces, the net sediment analysis for years, the long periods of monitoring, and the guide line and revision of the rule for coastal erosion.

해빈류 벡터 장미도를 통한 해운대 해수욕장의 이안류 민감도 분석

Rip current forecasts, based on intensity, are marked in four levels&#x2014;notice, watch, warning, and danger. However, numerical results are represented by current vectors, whose magnitudes are then converted into predictive levels. In the present study, the rose diagram is adapted as a determinative forecasting index and examined for the case of an ideal rip channel consisting of surface, bottom, and averaged currents. Further, it is employed in the sensitivity analysis of wave-induced currents generated by wave conditions at the Haeundae Beach. The simulation of surface onshore and bottom undertow currents is accomplished by including a mass flux term in the wave-averaged continuity equation.

The influence of waves on the tidal kinetic energy resource at a tidal stream energy site

Successful deployment of tidal energy converters relies on access to accurate and high resolution numerical assessments of available tidal stream power. However, since suitable tidal stream sites are located in relatively shallow waters of the continental shelf where tidal currents are enhanced, tidal energy converters may experience effects of wind-generated surface-gravity waves. Waves may thus influence tidal currents, and associated kinetic energy, through two non-linear processes: the interaction of wave and current bottom boundary layers, and the generation of wave-induced currents. Here, we develop a three-dimensional tidal circulation model coupled with a phase-averaged wave model to quantify the impact of the waves on the tidal kinetic energy resource of the Fromveur Strait (western Brittany) - a region that has been identified with strong potential for tidal array development. Numerical results are compared with in situ observations of wave parameters (significant wave height, peak period and mean wave direction) and current amplitude and direction 10m above the seabed (the assumed technology hub height for this region). The introduction of waves is found to improve predictions of tidal stream power at 10m above the seabed at the measurement site in the Strait, reducing kinetic energy by up to 9% during storm conditions. Synoptic effects of wave radiation stresses and enhanced bottom friction are more specifically identified at the scale of the Strait. Waves contribute to a slight increase in the spatial gradient of available mean tidal stream potential between the north-western area and the south-eastern part of the Strait. At the scale of the region within the Strait that has been identified for tidal stream array development, the available mean spring tidal stream potential is furthermore reduced by 12% during extreme waves conditions. Isolated effects of wave radiation stresses and enhanced bottom friction lead to a reduction in spring tidal potential of 7.8% and 5.3%, respectively. It is therefore suggested that models used for tidal resource assessment consider the effect of waves in appropriately wave-exposed regions.

Three-dimensional unstructured modelling of wave-induced circulation over a plane and irregular beach

Nearshore currents have a complicated circulation structure over a beach due to the mutual interaction between waves and currents. To investigate the wave-induced circulation over a beach, a three-dimensional unstructured model accounting for the combined actions of waves and currents is established. The wave distribution over the beach is computed by a wave model and the depth-dependent wave radiation stresses with the surface roller are employed in the hydrodynamic model. The present model takes the mixing coefficients and the bottom shear stress under waves and currents into account. To evaluate the three-dimensional unstructured model, the laboratory experiments over a plane and irregular beach are used to test the performance of the model. The undertow over a plane beach is well reproduced and the vertical variability is captured. The performance of the model over an irregular beach is well displayed in the reproduction of pairs of counter-rotating primary circulations at the embayment troughs. Meanwhile, the secondary circulations are observed in the swash zone. The model captures the circulation systems over a beach and the circulation structures of the wave-induced currents are well exhibited.

Wave-induced current simulated by wave–current coupled model in Haeundae

ABSTRACT Lim, H.S.; Chun, I.; Shim, J.S., and Kim, C.S., 2016. Wave-induced current simulated by wave–current coupled model in Haeundae. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1392 - 1396. Coconut Creek (Florida), ISSN 0749-0208. The wave-induced current in Haeundae, at the southeastern end of the Korean Peninsula, is one of the main causes of beach erosion. The Korean government recently initiated a beach restoration project for Haeundae beach to protect the famous beach against wave-induced currents generated by waves during summer and winter. To mitigate beach erosion, two submerged breakwaters and a sand nourishment program were initiated in 2013. With the support of the Korean government, we have also started an R&D project to develop coastal erosion control technology in order to understand the processes of beach erosion by measurin...

Applicability of 3D Beach Evolution Model with Wave-current Interaction to River-mouth Bar Formation

ABSTRACT Kuroiwa, M.; Shibutani, Y.; Yasumoto,; Mase, H, and Matsubara, Y., 2016. Applicability of 3D beach evolution model with wave-current interaction to river-mouth bar formation. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 73–77. Coconut Creek (Florida), ISSN 0749-0208. A coastal area model with wave-current interaction was presented, and then the performance and applicability of the numerical to morphodynamics around river mouths due to waves, wave-induced currents and river flows were investigated. First, model tests were carried out under a variety of wave and river discharge conditions to investigate their capability of predicting the formation of sand spit and terrace topographies. Second, model verification using a field site was conducted and the applicability was investigated. From the computed results, it was confirmed that the p...

Characteristics of Wave-induced Currents using the SWASH Model in Haeundae Beach

본 연구에서는 SWASH 모형을 이용하여 ê³„ì ˆë³„ 이상파랑에 의한 해운대 해수욕장에서 불규칙파의 파랑 변형 및 해빈류 특성을 분석하였다. 개경계에서 불규칙파는 JONSWAP 스펙트럼을 ì ìš©í•˜ì˜€ë‹¤. ìž ì‚¬íŒŒ 조건은 국립해양조사원에서 ì œê³µí•˜ëŠ” 2014ë „ 파랑관측자료를 바탕으로 ê³„ì ˆë³„ 대표파를 ì„ ì •í•˜ì˜€ë‹¤. SWASH에 의한 ê³„ì ˆë³„ 해빈류 계산결과는 현장조사 결과와 ë¹„êµÂ·ê²€í† í•˜ì˜€ë‹¤. 하계의 경우 S 계열의 파랑이 ì§€ë°°ì ì´ë©° 동백섬측에서 미포측으로 연안류가 ì§€ë°°ì ìœ¼ë¡œ ë°œìƒí•˜ì˜€ê³ í•´ìš´ëŒ€ 해수욕장 중앙부근에서는 이안류가 발생하였다. 동계의 경우 ESE 계열의 파랑이 ì§€ë°°ì ì´ë©° 해운대 해수욕장 중앙부근에서 각각 동백섬측과 미포측으로 향하는 연안류가 발생하였다. 핵심용어: 해빈류, 연안류, 이안류, 쇄파, 불규칙파

Wave Transformation using Modified FUNWAVE-TVD Numerical Model

The present modified FUNWAVE-TVD model, which is a modification to its previous version 2.1, is applied to solitary wave propagation and is tested against the experiments of Vincent and Briggs(1989) and Luth et al.(1994). The eddy viscosity breaking scheme is used for comparison with the existing study in the case of breaking experiment. The symmetry of wave-induced current is maintained when the modified model is employed to Vincent and Briggs(1989) breaking experiment, but the symmetry of wave-induced current in previous model is not maintained. A better agreement with the breaking experimental data is obtained in the modified model using eddy viscosity breaking scheme than the shock capturing breaking scheme using nonlinear shallow water equation. For comparison with the schemes in the model, the fourth order MUSCL-TVD scheme by Erduran et al.(2005) and the third order MUSCL-TVD scheme using minmod limiter is applied, and the numerical solutions of solitary wave are compared.

Sedimentary Facies and Depositional Environment of the Middle Devonian Geneseo Formation of New York, U.S.A.

Abstract Detailed facies characterization of the Middle Devonian Geneseo Formation in the Northern Appalachian Basin (NAB) shows a rich assembly of sedimentary features and textures that suggest shelfal mud deposition in a storm-dominated, shallow epeiric sea. At the time of deposition, Acadian uplift supplied fine-grained detritus from the east and stimulated delta growth. As sediment was shed from the hinterland, distribution of mudstone facies was controlled by a combination of autogenic processes and a general rise in sea level. The vertical and lateral distribution of nine mudstone facies observed in this succession indicates an overall shallowing-upwards trend (westward progradation of Catskill delta) with multiple modes of sediment transport and deposition. The water column became more oxygenated upsection as indicated by an increase in benthic fauna diversity (e.g., Leiorhynchus and Orbiculoidea), increasing bioturbation diversity (e.g., Chondrites, Palaeophycus, Planolites, Teichichnus, Thalassinoides, and Zoophycos), and a decline of organic-carbon content (via oxidation and consumption). Physical and biological attributes of this mudstone-dominated succession are used to reconstruct sedimentary processes and depositional conditions. Although a stratified-basin model has previously been proposed for the Geneseo Formation, observations made in this study do not support that interpretation. Collectively, our observations indicate shelfal mud deposition above storm-wave base, in a relatively energetic environment with persistent lateral transport and advection by oscillatory flow, wave-induced currents, river-flood, and storm-wave generated offshore-directed underflows, as well as storm setup-relaxation flows.

Random wave-induced current on mild slopes

This paper provides a simple analytical method for calculating the wave-induced current due to long-crested random waves on mild slopes. The approach is based on assuming the waves to be a stationary random process, adopting the Battjes and Groenendijk (2000) wave height distribution for mild slopes. An example is included to demonstrate the application of the analytical method for practical purposes using data typical for field conditions; the significant values of the surface Stokes drift and the volume Stokes transport are calculated. The present results can be used to make assessment of the random wave-induced current based on available wave statistics.