Hydrodynamics theory水动力学参数设定ppt整理.ppt

水动力学理论 控制方程 地形的处理 空间网格的选取 时间步长的选取 干湿区的定义 初始条件 边界条件 边界的处理 边界的倾斜 Land Boundary 源汇项的设置 数值涡粘系数 底床糙率 结果 MIKE 21模型溢出的多种原因 三个关系是否合理？ 时间步长 v.s. 空间步长 = 模型设置的推荐取值 Smagorinsky 常数 0.25-1 干湿区水深差 0.1-0.2m 扩散系数 MIKE 21模型的率定参数 糙率 – 水深和流速 涡粘系数 – 流速 （风阻力系数）– 水深和流速 扩散系数 – 污染物浓度变化 衰减系数 – 污染物浓度变化 MIKE 21 HD典型的出错信息 One point wide open flux boundary Elevation too low on flooded boundary Very high water level at (x, y) of area 1 …… * * Variables: Water level H (=Z+D) Flux in s-direction P (=H·U) Flux in n-direction Q (=H·V) Continuity equation Momentum equation Dynamic 2-D Saint Venant Equations flow acceleration convective and cross-momentum pressure gradients (surface slope) bed shear stress, e.g. Manning, Manning-Strickler, Chezy momentum dispersion, e.g. Smagorinsky coriolis force wind shear (not included, but prepared) Assumptions: shallow water hydrostatic pressure uniform density sub-critical flow no secondary circulation Land value- Permanent land- Permanent water- Alternating dry/wet Shallow-water assumption ?s depth and ?n depth, ?s 3?D , depth D Resolve bathymetry, typical length scale L ?s L/n , ?s L/5 Resolve flow adaptation, typical length scale λ?s λ /n λ=D*C2/2g, ?s λ /5 L Courant number CR Permanent land Permanent water Alternating dried and wetted Falling water level Rising water level Drying Depth 0.1 – 0.2 m Flooding Depth 0.2 – 0.4 m Drying depth always smaller than flooding depth. (for stability) Mass balance maintained. Represent ”sub-grid” geometry and processes Hot start one dsf2 file with bathy, ho, po, qo ,flood/dryo, start time, dt? Used after initial hydrodynamic model is established Cold start dsf2 file with bathy, separate specification of initial surface level (dfs2 file or constant) ? Used in the first hydrodynamic model setup. Often with small dt.