Simulation And Analysis Of The Silting Mechanisms In Conceptual Estuary And Yangtze Estuary

Estuary is the terminal of river,the interactional area between river and sea.Due to the influence of runoff,tide,wind,wave,density flow,storm surge and other natural factors,in addition to the role of the various kinds of engineering constructions,the hydrodynamic condition and sediment movement characteristi of estuary are generally complex,making it uneasy to study and understand estuarine sediment silting mechanisms.Based on the two-dimensional water-sediment numerical simulation,from the perspective of generalized estuary,this acticle simulates and analyzes several estuarine deposition mechanisms by simplifying estuarial morphology.In addition,the two-dimensional water-sediment mathematical model of Yangtze river estuary was built to simulate and analyze the flow,sediment movement and deposition mechanisms of this region.The specific contents and conclusions are as follows.1st,summarize and put forward five kinds of estuarine sediment deposition mechanisms: 1)the way of river section broadening,which means when river estuary section broadens,the flow velocity and sediment-carrying capacity reduce,making sediment falls and silts;2),the way of tide and runoff jacking,refering to the Sedimentation happens in stagnant areas where the strength of tide and runoff banlance;3),the way of river regime unsmooth,happening regularly when the angle between the hydrodynamics axis and talweg of riverway(includes channel)is too large,or when ebb tide and flood tide have different hydrodynamics axis;4),the way of local circulation flow,which means the suspend sediment in groin field moves to the main channel under the action of local circulation in groin field;5),the way of density current plunging,which means sediment in the groin field plunges into the channel in the form of density current and causes deposition.2nd,corresponding to several kinds of silting mechanisms,this arcticle establishes four mathematical models of conceptual estuary.Based on simulating the flow,sediment movement and deposition condition,it analyses the deposition mechanisms and deposition process of conceptual estuary.3rd,on the basis of simulating and analyzing conceptual estuary models,the Yangtze estuary 2-D water-sediment mathematical model is established to simulate and analyze the flow,sediment movement,scouring and silting in flood season of Yangtze estuary.Through the model calibration and parameter modification,it reveals that the model calculation result is accurate enough.4th,in perspective of section broadening,tide and runoff jacking,the river regime unsmooth,local local circulation flow,density current plunging,combining with the model simulation results of scouring and silting in the Yangtze river estuary,analyze the reason sediment deposit in different area,especially the deposition in the North Passage deep-water channe.It turns out that different area of Yangtze river estuary has different way of silting.