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Wave shoaling and diffraction in current over a mild-slope
LI Yucheng, LIU Deliang, CHEN Bing, LI Linpu
2004(4): 741-746.
Keywords: wave, current, mild-slope equation, diffraction
The wave relative frequency in the coordinate system moving with current and the angle between the direction of wave propagation and that of current are computed based on the wave dispersion relation.The current field is computed by solving the depth averaged shallow water equations.The wave field is computed by solving the mildslope equation which has taken the current's effect into account.A numerical model is established using a finite element method for simulating the wave shoaling and diffraction in current over a mild-slope,and the numerical results are reasonable to compare with the experimental data.
A study on the relationships between the wave height and the El Niño in the north area of the South China Sea
HAN Shuzong, FAN Yongbin, DONG Yangyang, WU Shuangquan
2017, 36(5): 44-50. doi: 10.1007/s13131-017-1059-2
Keywords: South China Sea, SWAN, wave, significant wave height, El Niño
On the basis of the European Centre for Medium-range Weather Forecasts (ECMwF) 20 a wind field reanalysis data, the wave field of the north area of the South China Sea is calculated with the combination of the HIRHAM wind field model and the SWAN wave model. Then a significant wave height compared with the El Niño index to study the relationships between these variables. The following conclusions are drawn:(1) the wave height of the South China Sea has a strong seasonal variation, the wave height is much larger in winter than in summer; (2) in the South China Sea, the monthly average wave height of the north area has a negative correlation with the Niño3.4 index, most area of the South China Sea has a moderate correlation and the area between Taiwan Province of China and Philippines is highly correlated; and (3) in the strong El Niño years, the significant wave height in the north area of the South China Sea is significantly smaller than in other years; if the El Niño index variability is greater, the wave height decreases. In contrast, the significant wave height in the north area of the South China Sea is larger in the strong La Niña years.
Sea spray induced air-sea heat and salt fluxes based on the wave-steepness-dependent sea spray model
Xingkun Xu, Joey J. Voermans, Changlong Guan, Alexander V. Babanin
2023, 42(5): 35-41. doi: 10.1007/s13131-022-2073-6  Published:2023-05-25
Keywords: sea spray, air-sea heat fluxes, air-sea salt fluxes, wave
Sea spray, which comprises amounts of small ocean droplets, plays a significant role in the air-sea coupling, atmospheric and oceanic dynamics, and climate. However, it remains arduous to arrive at estimates for the efficiency and accuracy of the sea spray induced air-sea heat and salt fluxes. This is because the microphysical process of sea spray evolution in the air is of extreme complexity. In this study, we iteratively calculated the sea spray induced air-sea heat and salt fluxes at various weather condition. To do so, we implemented one novel wave-steepness-dependent sea spray model into a bulk air-sea fluxes algorithm and utilized other sea spray models as comparisons. Based on the improved wave-dependent bulk turbulent algorithm, we observed that despite the negative contribution of sea spray to the sensible heat fluxes, the sea spray positively contributes to the air-sea latent heat fluxes, leading to an overall increase in the total air-sea heat fluxes. The additional heat fluxes caused by sea spray may be the missing critical process that can clarify the discrepancies observed between measured and modelled Tropical Cyclone’s development and intensification. In addition to heat fluxes, we observed that sea spray has significant impacts on the air-sea salt fluxes. As the sea salt particles are one of the main sources of the atmosphere aerosol, our results imply that sea spray could impact global and regional climate. Thus, given the significance of sea spray on the air-sea boundary layer, sea spray effects need to be considered in studies of air-sea interaction, dynamics of atmosphere and ocean.
A model for calculating the erosion distance of soft sea cliff under wave loading
CHANG Fangqiang, SHU Zhonglei
2018, 37(7): 69-77. doi: 10.1007/s13131-018-1245-x
Keywords: wave, soft sea cliff, erosion
A model for calculating the erosion distance of soft sea cliff under wave loading is established based on the erosion mechanism of soft sea cliff under wave loading and for considering wave hydrodynamic and sea cliff material parameters. The model is verified, and the parameters are regressed using an indoor flume experiment. The erosion distances of the sea cliff in the northeast of the Pingtan Island are calculated by the model, and the results are compared with the measured data. The maximum erosion occurs in static water level, the location of the maximum erosion moves up as the wave continues, and the erosion stops when the wave lasts for a period of time. The erosion does not occur until the wave height exceeds a critical value; however, the contribution of large waves to the erosion is not relatively substantial. The calculated erosion distances at two places in the northeast of Pingtan Island are 0.32 m and 0.26 m.
The controlling factors of high suspended sediment concentration in the intertidal flat off the Huanghe River Estuary
Bowen Li, Yonggang Jia, J. Paul Liu, Jianfeng Su, Xiaolei Liu, Mingzheng Wen
2020, 39(10): 96-106. doi: 10.1007/s13131-020-1679-9  Published:2020-10-25
Keywords: Huanghe River (Yellow River), sediment re-suspension, sediment transport, wave, current, in-situ observation
The Huanghe River (Yellow River) is known by its high suspended sediment concentration (SSC) in its river mouth tidal flat. However, the factors controlling the high SSC over there are not well understood. Therefore, we conducted 7-d hydrodynamic observations (water depth, wave height, and current velocity) and SSC measurements on the tidal flat off the Huanghe River Mouth. The data shows that in most of time, under the calm sea condition, the SSC ranges 0.1–3.5 g/L, and sediment discharge from the river is the main source. However, when hydrodynamics are enhanced in a tidal cycle and large-scale erosion occurs on the seafloor, resuspended sediment becomes the main source, and the SSC in the water column reaches 17.3 g/L. We find the suspended sediment flux is mainly controlled by the tidal current and Stokes drift, while the wave-induced shear stress could also affect the variation of suspended sediment flux. During the observation period, when sea under calm-rippled conditions, the current-induced resuspended sediment concentration (RSC) was greater than the wave-induced RSC. In contrast, in smooth-wavelet sea conditions, the wave-induced RSC was greater than the current-induced RSC, for instance, a single wave event was found to cause 11.8 cm seabed erosion within 6 h. This study reveals different controlling factors for the high SSC near a river-influenced tidal flat, and helps us get a better understanding of a delta's depositional and erosional mechanisms.
Variations of suspended sediment transport caused by changes in shoreline and bathymetry in the Zhujiang (Pearl) River Estuary in the wet season
Shicheng Lin, Jianwei Niu, Guangping Liu, Xing Wei, Shuqun Cai
2022, 41(10): 54-73. doi: 10.1007/s13131-022-2017-1  Published:2022-10-27
Keywords: suspended sediment concentration, wave, bottom stress, estuarine turbidity maximum, numerical model, Zhujiang (Pearl) River Estuary
A wave-current-sediment coupled numerical model is employed to study the responses of suspended sediment transport in the wet season to changes in shoreline and bathymetry in the Zhujiang (Pearl) River Estuary (ZRE) from 1971 to 2012. It is shown that, during the wavy period, the large wave-induced bottom stress enhances sediment resuspension, resulting in an increase in the area of suspended sediment concentration (SSC) greater than 100 mg/L by 183.4%. On one hand, in spring tide, the change in shoreline reduces the area of SSC greater than 100 mg/L by 17.8% in the west shoal (WS) but increases the SSC, owing to the closer sediment source to the offshore and the stronger residual current at the Hengmeng (HEM) and Hongqili (HQL) outlets. The eastward Eulerian transport is enhanced in the WS and west channel (WC), resulting in a higher SSC there. The reclamation of Longxue Island (LXI) increases SSC on its east side and east shoal (ES) but decreases the SSC on its west and south sides. Moreover, in the WC, the estuarine turbidity maximum (ETM) is located near the saltwater wedge and moves southward, which is caused by the southward movement of the maximum longitudinal Eulerian transport. In neap tide, the changes are similar but relatively weaker. On the other hand, in spring tide, the change in bathymetry makes the SSC in the WS increase, and the area of SSC greater than 100 mg/L increases by 11.4% and expands eastward and southward, which is caused by the increases in wave-induced bottom stress and eastward Eulerian transport. On the east side of the WC, the eastward Eulerian transport decreases significantly, resulting in a smaller SSC in the middle shoal (MS). In addition, in the WC, the maximum SSC is reduced, which is caused by the smaller wave-induced bottom stress and a significant increase of 109.88% in southward Eulerian transport. The results in neap tide are similar to those in spring tide but with smaller changes, and the sediment transports northward in the WC owing to the northward Eulerian transport and vertical shear transport. This study may provide some references for marine ecological environment security and coastal management in the ZRE and other estuaries worldwide affected by strong human interventions.
Numerical modelling of sand beach evolution around coastal structures
Zhang Haiwen, Tao Jianhua
2000(2): 127-136.
Keywords: Wave, nearshore current, Sand beach evolution
A systematic study of waves,nearshore currents and sediment transport related to the coastal evolution of sand beach under the action of wave,has been carried out.On the basis of the resalts,a numerical model of sand beach evolution around coastal structures has been established.To predict the bed topography,the sediment transport rates of bedload and suspended load under the action of wave and nearshore current as well as the effects of wave on the sediment are wnsidered.The sand beach evolutions caused by a breakwater and a settled ship near the shore are simulated.
Numerical modeling of wind and waves for Typhoon Betty (8710)
Yu Weidong, Qiao Fangli, Yuan Yeli, Pan Zengdi
1997(4): 459-473.
Keywords: Typhoon, wave, numerical modelling
Wind and wave fields are hindcasted for Typhoon Betty (8710), using LAGFD-WIN dynamical wind model end LAGFD-NWM third genezation wave model.The results are satisfying, which validates the models and shows their reliability for strong sea state.An idea is brought out that wind input source function should be improved, including the effects of wind guatness and wave age factor.The present work makes preliminary preparations for the regional oceanography study of the South China Sea, also provides the technical supports for ocean engineering design.
Numerical simulation of sediment lifted by waves and transported by tidal currents
Cao Zude, Wang Guifen
1994(3): 433-443.
Keywords: Wave, tidal current, numerical model, sediment movement, bed processes
The analysis of the seabed processes of a muddy coast has been described in this paper.On the basis of the basic differential equation of tidal current and sediment movement influenced by waves,a numerical simulation system for sediment lifted by waves and transported by tidal currents and seabed processes has been established by using MADI method,and applied to the sea area of Tianjin Port with good results.
A vortex induced vibration of marine riser in waves
LOU Min, DONG Wenyi, GUO Haiyan
2011(4): 96-101. doi: 10.1007/s13131-011-0139-y
Keywords: riser, VIV, wave, experiment
A marine riser transporting fluid in the Bohai Sea was selected as study object, using an experimental and numerical method to study its vortex induced vibration in waves. A similarity theory was used in the experiment to derive the experimental model from a practical model, the dynamic response of a riser model was measured in waves. A corresponding numerical simulation was performed using a finite element method. Comparisons were made with the results between the experiment and the numerical simulation. Some valuable results were obtained.
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