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1、1. 管网水动力介绍城市管网模型MIKE URBAN 整合了ESRI的ArcGIS、排水管网系统CS和给水管网WD形成了一套城市水模拟系统。MIKE URBAN建立在AO(ArcObject)的构架基础上，工程文件采取Geodatabase数据库作为存储格式，这使得urban与GIS具有天然的联系，可以提供强大的GIS功能。该模型广泛应用于城市排水与防洪、分流制管网的入流/渗流、合流制管网的溢流、受水影响、在线模型、管流监控等方面。其水动力学模型选用DHI开发研制的管流模型采用MOUSE标准模块 - 管流模块。在管流模块中，先进的计算公式使模型能够准确描述各种水流现象和管网元素如灵活的横截面形
2、状，包括标准形状、圆形人孔（检查井）、蓄水区溢流堰泵站操控、水流调节构件、恒定或随时间变化的出口水位、恒定的或随时变化的入流流量、人孔/集水区的水头损失、随深度变化的摩擦系数等。 Mouse水动力学计算基于动态流St.Venant方程组即连续性方程（质量守恒）和动量方程（动量守恒-牛顿第二定律）： (3.2) (3.3)式中Q为流量；A为过流面积；y为水深；g为重力加速度；x为水流方向的距离；t为时间；为速度分配系数；I0为管底坡度；If为摩擦比降。方程组利用Abbott-Ionescu六点隐式格式求解，离散格式如图5-15所示。该格式在每一个网格点并不同时计算水位和流量，而是按顺序交替计算水
3、位或流量，分别称为h点和Q点。Abbott-Ionescu格式具有稳定性好、计算精度高的特点。离散后的线形方程组用追赶法求解。2. 芝加哥雨型介绍The Chicago hyetograph is assumed to have a time distribution such that if a series of ever increasing “time-slices” were analyzed around the peak rainfall, the average intensity for each “slice” would lie on a single curve of
4、the IDF diagram. It implies that the Chicago design storm displays statistical properties that are consistent with the statistics of the IDF curve. The synthesis of the Chicago hyetograph, therefore, starts with the parameters of an IDF curve together with a parameter (r), which defines the fraction
5、 of the storm duration that occurs before the peak rainfall intensity. The value of r is derived from the analysis of actual rainfall events and is generally in the range of 0.3 0.5.The continuous curves of the hyetograph in Figure 3.6 can be computed in terms of the times before (tb) or after (ta)
6、the peak intensity by the two equations below.a) After the peakb) Before the peakwhere: ta = time after peaktb = time before peakr = ratio of time before the peak occurs to the total duration timeThe Chicago storm is commonly used for small to medium watersheds (0.25 km2 to 25 km2) for both rural or
7、 urbanized conditions. Typical storm durations are in the range of 1.0 to 4.0 hours. It has been found that peak runoff flows computed using a Chicago design storm are higher than those obtained using other synthetic or historic storms. This is due to the Chicago storm attempts to model the statistics of a large collection of real storms and thus tends to present an unrealistically extreme distribution. Another point to note is that the resultant peak runoff may exhibit some sensitivity to the time step used; very small time steps giving rise to slightly more peaked runoff hydrographs.3.
