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Engineering application of submerged water jets for sediment removal in a tidal riverbed

Water Science and Engineering 2022年第4期15卷 348-357页

作者： Chaiyuth Chinnarasri King Mongkut's University of Technology Thonburi Bangkok 10140Thailand

sediment deposition problems have attracted the interest of engineers and researchers.Several experimental studies have been conducted on scour depth using turbulent jets.However,field observation and monitoring have rarely been reported.This study aimed to eliminate sediments on a tidal riverbed using a prototype device,which consisted of a set of submerged vertical water nozzles and submerged horizontal air nozzles.The effectiveness of the water jet in sediment removal during spring and neap tides was evaluated.The quantitative relationships of dimen-sionless parameters,such as(1)the relative sediment scour volume versus the number of flows from the jet exit,(2)the relative sediment scour volume versus the relative scour depth,and(3)the relative scour size versus the relative jet intensity,were analyzed.The results showed that the freshwater flowing to the sea affected the sediment scour volume during the falling cycle of spring tides.In contrast,the rising cycle of spring tides retarded the freshwater flow,resulting in a decrease in the sediment scour volume.A steep water surface slope accelerated the river flow and further influenced the cross-flow current around the study area.As a result,a highly diffusive turbulent flow was produced,causing sus-pended sediments to be rapidly removed from the scour hole center.An increase in the number of flows from the jets led to intensified diffusion of turbulent energy into the flow.The rapidly varying water depth caused jet energy to be dissipated before approaching the riverbed,and it significantly affected the scour process during the spring-tide period.The proposed equations can be used to estimate the scour volume,scour size,and re-suspended sediments in tidal rivers within defined ranges of parameters.

关键词： Jet diffusion Scour hole sediment re-suspension Tidal river Field experiments

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The controlling factors of high suspended sediment concentration in the intertidal flat off the Huanghe River Estuary

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Acta Oceanologica Sinica 2020年第10期39卷 96-106页

作者： Bowen Li Yonggang Jia J.Paul Liu Jianfeng Su Xiaolei Liu Mingzheng Wen Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Ocean University of ChinaQingdao 266100China Laboratory for Marine Geology Pilot National Laboratory for Marine Science and Technology(Qingdao)Qingdao 266237China Department of Marine Earth and Atmospheric SciencesNorth Carolina State UniversityRaleighNC 27695USA State Key Laboratory of Marine Geology Tongji UniversityShanghai 200092China Tianjin Center China Geological SurveyTianjin 300170China

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.

关键词： Huanghe River(Yellow River) sediment re-suspension sediment transport wave current in-situ observation

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TOTAL PHOSPHORUS reLEASE FROM BOTTOM sedimentS IN FLOWING WATER

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Journal of Hydrodynamics 2012年第4期24卷 589-594页

作者： ZHANG Kun CHENG Peng-da ZHONG Bao-chang WANG Dao-zeng Shanghai Institute of Applied Mathematics and Mechanics and Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai UniversityShanghai 200072China

In this paper, the bottom of the Dianshan Lake was selected as a test sample. The dynamic release of contaminated sediments into the overlying water column was experimentally investigated in an open water channel under different hydrodynamic conditions. The experimental results indicate that the Total Phosphorus （TP） release process can be divided into three stages： rapid release, slow release and equilibration release. In the initial release stage the measured TP concentration changes along the depth. The TP concentration near the sediment-water interface is higher than that near the water surface, but the TP concentration becomes uniform along the depth after 3 h. The dynamic release of re-suspension sediment pollutants is about 6 times higher than the static release of sediment-water interface. There are three main types of release mechanism： diffusion release, re-suspended pore water mixing release and re-suspended particles desorbing release.

关键词： Total Phosphorus （TP） concentration sediment re-suspension overlying-water release mechanism

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