半日潮流作用下悬移质泥沙的运动特征及其影响因素研究
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摘要
本文通过建立一维水深平均悬沙模型,对典型潮流控制的水道内悬沙运动特征进行研究。模型以泥沙再悬浮、沉降和平流为主要物理过程,动力因素包含M_2、S_2分潮及余流,采用湄洲湾2007年8月潮位、潮流、悬沙、底质同步观测资料进行分析和验证。通过三角傅里叶分析,将悬沙的时间序列分解为12个主要的谐波分量,其中主要分量包括:M_2分潮作用下产生的具有M_2倍潮角速度的1/4日分潮项,M_2与S_2分潮共同作用下且角速度为两分潮角速度之和的1/4日分潮项,及水平悬沙梯度、余流与M_2分潮共同作用下具有M_2分潮角速度的半日潮项。悬沙在时间上的平均值受到余流、悬沙水平梯度、M_2分潮流及悬沙起动条件等因素控制。余流导致了悬沙序列中相邻周期之间的不对称性。反映泥沙特性的参量对悬沙的曲线特征具有重要影响,泥沙沉降速度影响悬沙的相位,并影响其振幅;再悬浮有关的参量仅影响各谐波分量的振幅,但不影响相位。
To study the sediment movement characteristics in a tidal channel, an one-dimensional depth-averaged suspended sediment concentration(SSC) model is established including advection, resuspension and deposition as main physical processes. The hydrodynamic force contains M_2 and S_2 tides. The model was applied in Meizhou Bay, in which tide, current, SSC and the sediment were measured or sampled in August, 2007. And the model was validated by the observation data. Suspension was decomposed into 12 primary terms by Fourier analysis, including(1) a demisemi-diurnal term induced by M_2 tide with an angular velocity of the overtide of M_2,(2) a demisemi-diurnal term induced by the combined action of M_2 and S_2 tides with an angular velocity of the sum of the angular velocities of M_2 and S_2, and(3) a semi-diurnal term induced by the combined action of horizontal suspension concentration gradient, residual current and M_2 tide, with an angular velocity same to that of M_2 tide. The time average of SSC is mainly controlled by residual current, horizontal gradient of suspension concentration, M_2 tidal current, and the incipient condition of sediment. The residual current could cause the asymmetry of suspension between the adjacent periods. The feature of SSC curve is controlled by the sediment parameters which reflect the sediment characteristics. The deposition parameters influence both the phase and the amplitude of SSC. The resuspension parameters only influence the amplitude of SSC, nor did the phase.
To study the sediment movement characteristics in a tidal channel, an one-dimensional depth-averaged suspended sediment concentration(SSC) model is established including advection, resuspension and deposition as main physical processes. The hydrodynamic force contains M_2 and S_2 tides. The model was applied in Meizhou Bay, in which tide, current, SSC and the sediment were measured or sampled in August, 2007. And the model was validated by the observation data. Suspension was decomposed into 12 primary terms by Fourier analysis, including(1) a demisemi-diurnal term induced by M_2 tide with an angular velocity of the overtide of M_2,(2) a demisemi-diurnal term induced by the combined action of M_2 and S_2 tides with an angular velocity of the sum of the angular velocities of M_2 and S_2, and(3) a semi-diurnal term induced by the combined action of horizontal suspension concentration gradient, residual current and M_2 tide, with an angular velocity same to that of M_2 tide. The time average of SSC is mainly controlled by residual current, horizontal gradient of suspension concentration, M_2 tidal current, and the incipient condition of sediment. The residual current could cause the asymmetry of suspension between the adjacent periods. The feature of SSC curve is controlled by the sediment parameters which reflect the sediment characteristics. The deposition parameters influence both the phase and the amplitude of SSC. The resuspension parameters only influence the amplitude of SSC, nor did the phase.
引文
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[3] Tian Tian,Merico A,Su Jian,et al.Importance of resuspended sediment dynamics for the phytoplankton spring bloom in a coastal marine ecosystem[J].Journal of Sea Research,2009,62(4):214-228.
[4] Guézennec L,Lafite R,Dupont J P,et al.Hydrodynamics of suspended particulate matter in the tidal freshwater zone of a macrotidal estuary (the Seine Estuary,France)[J].Estuaries,1999,22(3):717-727.
[5] van de Kreeke J,Hibma A.Observations on silt and sand transport in the throat section of the Frisian Inlet[J].Coastal Engineering,2005,52(2):159-175.
[6] Yu Qian,Wang Yaping,Flemming B,et al.Tide-induced suspended sediment transport:depth-averaged concentrations and horizontal residual fluxes[J].Continental Shelf Research,2012,34:53-63.
[7] Bass S J,Aldridge J N,McCave I N,et al.Phase relationships between fine sediment suspensions and tidal currents in coastal seas[J].Journal of Geophysical Research:Oceans,2002,107(C10):10-1-10-14.
[8] Stanev E V,Brink-Spalink G,Wolff J O.Sediment dynamics in tidally dominated environments controlled by transport and turbulence:a case study for the East Frisian Wadden Sea[J].Journal of Geophysical Research Oceans,2007,112(C4):C04018.
[9] Uncles R J,Stephens J A.Distributions of suspended sediment at high water in a macrotidal estuary[J].Journal of Geophysical Research Oceans,1989,94(C10):14395-14405.
[10] Dronkers J.Tide-induced residual transport of fine sediment[M]//Physics of Shallow Estuaries and Bays.Berlin:Springer-Verlag,1992:228-244.
[11] Cheng Peng,Wilson R E.Modeling sediment suspensions in an idealized tidal embayment:importance of tidal asymmetry and settling lag[J].Estuaries and Coasts,2008,31(5):828-842.
[12] Zhu Zichen,Wang Yongzhi,Bian Shuhua,et al.A method for simulating sediment incipient motion varying with time and space in an ocean model (FVCOM):development and validation[J].Journal of Oceanology and Limnology,2018,36(4):1216-1235.
[13] Hill D C,Jones S E,Prandle D.Derivation of sediment resuspension rates from acoustic backscatter time-series in tidal waters[J].Continental Shelf Research,2003,23(1):19-40.
[14] Aldridge J N.Optimal fitting of a model to observations of sediment concentrations in the Irish Sea[C]//Spalding M L,Cheng R T.Estuarine and Coastal Modelling Proceedings of the 4th International Conference.San Diego,USA:American Society of Civil Engineers,1996:417-428.
[15] Jago C F,Jones S E.Observation and modelling of the dynamics of benthic fluff resuspended from a sandy bed in the southern North Sea[J].Continental Shelf Research,1998,18(11):1255-1282.
[16] 陈居成.湄洲湾沉积物分布特征及泥沙来源[J].福建师范大学学报:自然科学版,1988,4(3):104-111.Chen Jucheng.A primary study on sedimental resource in Meizhou Bay[J].Journal of Fujian Teachers University:Natural Science,1988,4(3):104-111.
[17] van Ledden M,Wang Zhengbing,Winterwer H,et al.Sand-mud morphodynamics in a short tidal basin[J].Ocean Dynamics,2004,54(3/4):385-391.
[18] Amos C L,Daborn G R,Christian H A,et al.In situ erosion measurements on fine-grained sediments from the Bay of Fundy[J].Marine Geology,1992,108(2):175-196.
[19] Soulsby R.Dynamics of marine sands[C]//A Manual for Practical Applica.London:Thomas Thelford,1998.
[20] Xiong Jilian,Wang Xiaohua,Wang Yaping,et al.Mechanisms of maintaining high suspended sediment concentration over tide-dominated offshore shoals in the southern Yellow Sea[J].Estuarine,Coastal and Shelf Science,2017,191:221-233.