河控三角洲生长的动力和沉积模式

分析河口动力特征，进而揭示其控制下的三角洲前缘挟沙河流床沙载荷（推移质）搬运和沉积机制，是合理构建河控三角洲生长沉积模式的前提。运用流体力学的湍流理论从微观动力过程角度分析失去河床约束条件下依靠惯性作用流动的河水入湖过程中河、湖两类水体的相互作用机制及流动规律，结合水槽物理模拟及前人开展的数值模拟，并借鉴河流泥沙动力学理论成果，构建了受流体力学及河流泥沙动力学约束的河控三角洲生长的动力和沉积模式。结果表明:湍流的特点决定了两类水体界面处存在强烈的质量、动量、动能传递。河水入湖过程既不是圆形（轴对称）射流，也不是平面（二维）射流，而是矩形（三维）射流，流速沿程会以负指数快速衰减。河口是挟沙河流流速衰减的终点，其控制下的三角洲前缘是挟沙河流床沙载荷沉积的终点。三角洲平原砂体生长过程，是三角洲平原动力、沉积、地貌相互作用的过程，生长的动力和沉积模式可以概括为:河流末端水体流速沿程衰减→挟沙能力降低→泥沙沉积→河床抬高→堤岸决口→河流分叉→水体流速沿程衰减→挟沙能力降低→泥沙沉积。分流河道砂体构成三角洲平原的骨架砂体，地貌控制下河流的频繁摆动是三角洲平原砂体生长的重要机制。河控三角洲沉积的主体为平原环境，而非前缘环境。

Dynamic and Sedimentary Models of River-dominated Delta Growth

Analysis of the hydrodynamic characteristics of estuaries,and examination of the bedload transport and deposition processes of a sediment-carrying river in a delta front controlled by the estuary,are the premises of this study of the growth patterns of river-dominated deltas.Turbulence theory is applied from the perspective of microscopic dynamic processes to analyze the interaction mechanism and movement process of a river flowing into a lake.In this process,the river flows into the lake by inertia and without the constraints of a riverbed.Combining physical flume modeling and numerical simulation carried out for the growth process of a river-controlled delta with reference to the theory of fluvial sediment dynamics,the dynamic and sedimentary models of river-delta growth are established in terms of fluid dynamics and river sediment dynamics.The results show that the characteristics of turbulence determine the strong inertial mass,momentum and kinetic energy transfer between the two water bodies.The process of river water entering the lake is neither a circular(an axial),nor a plane(two-dimensional)jet,but a rectangular(three-dimensional)jet.The flow velocity in the lake is rapidly negative-exponentially attenuated.The estuary marks the termination of the sediment-carrying river,and the delta front under its control is its bedload terminal point.The growth process of delta plain sedimentary bodies consists of the delta plain power and the sedimentary and geomorphological interaction processes.The dynamic and sedimentary patterns may be summarized as:end of river-water flow;velocity attenuation along with reduction in carrying capacity and sediment deposition;river plate drive up to a bank run;river-tributary flow velocity with lower sedimentation;and distributary channel sandbodies.These produce the skeleton of sandbodies in a delta plain region.Frequent oscillation determined by river topography is also an important mechanism for the growth of delta plain sedimentary bodies.The main body of river-dominated delta deposition is determined by the plain environment,not the front environment.