1、Theoretical Background理论背景,MIKE 21/3 FM Mud Transport Module MIKE 21/3 FM泥模块,MIKE 21/3 MT FM:Theoretical Background理论背景,Introduction介绍Cohesive and non-cohesive sediment has different properties;粘性泥沙和非粘性泥沙的性质是截然不同的Question问题:What do we class as mud?什么是泥？Answer答案:Particle Sizes include:Silt:2-63m.Clay
2、:less than 2m;泥的颗粒粒径:粉沙:2-63m.粘土:小于2m;At this scale ionic charges interact electrostatically and affect the properties of sediment-fluid interaction(flocculation,turbulence damping etc.);在这个尺度上，颗粒所带的离子电荷作用，影响到了泥沙-水流的属性（絮凝，紊动阻力等）;Also,sediment properties are affected by organic material content;泥沙的属性
3、同时也受到有机物质的影响;Sand with a content of 10-20 per cent fine sediments treated as cohesive sediment.沙中有10-20%的细颗粒可以当作是粘性泥沙。,MIKE 21/3 MT FM:Theoretical Background理论背景,MIKE 21/3 FM MT:Solves the 3-D AD equation with diffusion coefficients that are dependant on fluid as well as mud properties;求解三维的对流扩散方程，其
4、中扩散系数考虑了流体和泥沙的属性,ws=fall velocityws=泥沙沉速,T=turbulent Schmidt no.T=湍流 Schmidt 数,T=anisotropic eddy viscosityT=各向异性涡粘系数,S i=source or sink termfor erosion or depositionSi=冲刷和淤积作为源和汇,MIKE 21/3 MT FM:Theoretical Background 理论背景,Source and sink terms:源、汇项：Deposition:for b ce(soft bed)(Parchure&Mehta,1985
5、)再悬浮（软底床）Erosion:for b ce(hard bed)(Partheniades,1963)侵蚀（硬底床）,Instantaneous bed shear stress(combined waves¤ts)瞬时底床切应力(波流耦合),Critical shear stress for deposition临界淤积切应力,Critical shear stress for erosion临界侵蚀切应力,MIKE 21/3 MT FM:Theoretical Background理论背景,Processes that are described in MT:MT中描述的
6、物理过程:Deposition and erosion rates are based on the critical bed shear stress concept(R.B.Krone 1962,Parchure and Mehta 1985,Partheniades,1963);沉积率和侵蚀率基于底床临界剪切应力的概念(R.B.Krone 1962,Parchure and Mehta 1985,Partheniades,1963);Flocculation and hindered settling included;包括絮凝和受阻沉降;Density driven mud flow
7、at high sediment concentrations;高含沙量下的密度驱动浮泥流（异重流）；Damping of turbulence over the lutocline at high sediment concentrations;高含沙量下紊动效应的衰减;Bed sediment variation in depth by a n layer bed description(n is typically 3,weak fluid mud,fluid mud and consolidated bed);底床泥沙分为n层描述（n一般为3，弱浮泥层，浮泥层和固结层）Consolid
8、ation in bed;底床的固结；Enhancement of bottom shear stress from short periodic surface waves;短周期波作用下底床剪切应力的增强；,Other features of the MT model:MT模型的其他特点:3D description based on the MIKE 3 FM Advection-Dispersion with inclusion of erosion-deposition terms;三维的MT模型基于MIKE-3 FM传输扩散模块，包含了侵蚀-沉积项；Applies the same
9、 mesh as MIKE 3 HD FM;使用和MIKE-3 FM水动力相同的网格地形Is solved simultaneously with MIKE 3 HD FM;和MIKE-3 FM水动力同时耦合计算；Spatially varying parameter settings allowing for effect of vegetation,biology and sediment inhomogenity;参数设置可以随空间变化，可以反映植被，生物和泥沙的不均一性。Can use boundary data from MIKE 21 FM;可以使用MIKE 21-FM的边界数据；
10、Multiple fractions and layers can be simulated.可以模拟多组分，多层底床。,MIKE 21/3 MT FM:Theoretical Background理论背景,Input parameters:输入参数：Settling velocity(measurable)沉降速度(实测)Flocculation(measurable)絮凝(实测)Dry density of bed layers(measurable)底床干密度(实测)Critical shear stress for erosion(experience/measurements)临界侵
11、蚀剪切应力(经验/实测)Thickness of bed layers or estimate of total amount of sediment in the system(measurements)底床厚度或模型中总的泥沙量(实测)Concentration at open boundaries(measured or modelled)边界处含沙量(实测或从大模型提取),MIKE 21/3 MT FM:Theoretical Background理论背景,Calibration parameters:率定参数：Dispersion coefficients 扩散系数Critical
12、shear stresses,for each layer 每个床层的临界剪切应力Erosion coefficients,for each layer 每个床层的侵蚀系数Power of erosion,for each layer 每个床层的侵蚀指数Transition coefficients between bed layers(consolidation)底床各层之间的转换系数(固结),MIKE 21/3 MT FM:Theoretical Background理论背景,Output Parameters 输出结果:Suspended sediment concentrations
13、in time series of 3D matrixes or 2D sections(horizontally or vertically)三维矩阵或两维断面的悬浮含沙量浓度时间序列（水平或垂直）Height or density of bed layers底床高度或密度Net sedimentation rates 净淤积率,MIKE 21/3 MT FM:Theoretical Background理论背景,Discussion and key points讨论与要点:Mud behaviour is extremely difficult to predict,and is subj
14、ect to intense research activity.The models that exist today are continuously being improved.对于泥沙运动规律的研究还远远不够，所以泥沙的运动很难预测。现在的泥沙模型处于不断改进中；It is important to define time scales of problem and modelled and choose an approach accordingly.定义问题的时间尺度并且选择相应的解决办法，这一点是很重要的；Sediment behaviour is dependant on t
15、he hydrodynamical conditions.If these are modelled correctly the trends and overall behaviour can be assessed adequately.泥沙的运动很大程度上取决于水动力条件。如果水动力模拟得足够准确，泥沙的运动趋势可以大体把握。Evaluation of relevant time scales for study is vital.i.e.for long term simulations(months),giving seasonal variations and trends is
16、more important than detailed process studies.评估相应的时间尺度极为重要，例如，对于长期模拟（几个月），给出季度变化和趋势，比研究详细的过程更重要。Biggest problem is the lack of reliable measurements with which to calibrate the models.Ideally we require:time series of SPM,in-situ measurements of fall velocities,detailed sediment maps.泥沙模拟最大的问题在于缺少可靠
17、的实测资料来率定模型。理想情况下，泥沙模型需要：SPM时间序列，实测沉降速度，详细的底床泥沙分布图。3D models can realistically only simulate shorter events.These events must be carefully selected such that the all important flow and sediment conditions are covered.由于计算耗时的限制，三维模型只能模拟较短的时段。这些时段应该经过精心挑选，能够包含所有重要的水动力条件和泥沙条件。,MIKE 21/3 MT FM:Theoretical Background理论背景,
