Study On Transport Characteristics Of Suspend Sediment In Yueqing Bay

The transport of suspended sediment in muddy bay is seriously considered when studying on the subjects, such as channels maintenance, coastal topography evolution, offshore engineering effect etc. The mechanism decomposition method, wavelet analysis and numerical simulation are used in this paper for Yueqing Bay, in which characteristics and mechanism of suspended sediment transport and distribution of suspended sediment concentration are studied. Three methods possess their own characteristics of academic tendency and are complement each other. The work has further improved suspended sediment transport studying, and is helpful for solving practical problems of sediment engineering.Based on the measured field data in 2006 summer and 2007 spring, firstly, the transport flux of suspended sediment is divided into several dynamic items through the mechanism decomposition method. The space-time distributional characteristics of suspended sediment transport and the dynamic mechanism of main items is examined after. Wavelet analysis is used for the analysis of the interaction of time domain and frequency domain between depth averaged velocity, depth averaged sediment concentration, sediment discharge of unit width. The periods of main items and its contribution for Sediment Transport are discussed combining these two methods. According to the models, both of two-dimensional uncoupled model and suspended sediment unbalance mathematical model, velocities and sediment concentration of feature stations near the measure ones can be achieved. The space-time distributional characteristics of suspended sediment concentration are studied by analyzing the net transport and the change of sediment concentration and transport rate.Wavelet analysis shows that:the relationship between Low-frequency part of the sediment and flow velocity,the relationship between sediment transport rate and sediment,flow rate there is significant regional variations; the main change cycle of sediment and sediment transport rate is 6.0-8.Oh; M2 tide in the main sediment cause different affect in the sediment transport processes:the main cycle of Euler residual runoff sediment is 12.4h, it play an important role in the low-frequency process in the deep zone; the low-frequency cycle of Stokes flow over sediment transport, tidal pumping sediment and vertical net circulation are 12.4h, the high frequency cycle of is about 6.2h which is the dominant contribution to the sediment transport in shallow water, which shows good agreement with the result of using mechanism decomposition method.Numerical analysis indicate that:Hua Qi flat in the outer bay, Da Hengchuang flat in the inner bay are in the trend of depositing, the tidal pumping is the main reason of sediment changes in shallow sediment, the main reason of causing sediment discharge is the sediment advection replace the tidal pumping in the deep water, which is completely consisitent with the result of using mechanism decomposition method and wavelet analysis.