目前國內應用於評估雨水下水道系統之數值模式，或因水文條件考慮之差異，或因沒有模式之原始程式無法做進一步之修正內部水理條件，無法有效且精確模擬雨水下水道系統複雜之各種水理現象。為建立一適合於國內長期使用且可長期修正率定之評估模式，本研究建構都市雨水下水道系統一維性非恆態流水理數值評估模式。 本研究之一維性非恆態流水理模式是應用普里司曼隱性差分技巧（Preissmann’s Scheme）及數值法模擬應用聖凡南假設（Saint Venant Hypotheses）而推導之連續式與動量方程式。藉由各子集水區之基底降雨強度及應用合理化公式而求得各管渠之基底流量。假設於恆態流況下，各管渠之初始水深藉由基底流量及下水道系統之上、下游邊界條件以標準步推法（Standard-Step Method）求得。下水道系統各子集水區之非恆態入流歷線可應用各種水文或水理模式建構；本研究暫時採用荷頓漫地流水文模式建構。水文模式可視實際需要而建構求得，並可直接輸入。因為側溝與集水陰井之影響較小，本研究假設各子集水區之入流流量直接經由水孔排入幹線。模式之下游條件可應用已知之下游河川水位資料或考慮抽水站抽水量而模擬。 本評估模式可模擬矩型與圓型管之明渠流與滿管壓力流水理現象；管渠配置可為匯流、分流及迴圈管網，而人孔、抽水站或任何水工結構物亦可於模式中建構。應用本模式於多種匯流、分流及管網系統以矩形及圓形兩種斷面形狀之渠道來模擬其水理現象，並根據其結果驗證本模式之可靠性。 We apply Preissmann’s scheme and Double Sweep Method to establish a model to solve Continuity Equation and Momentum Equation according to Saint Venant Hypotheses. The model can be applied to refer to design of the drainage system and estimate capability of the drainage system as a basis of improving drowned region. The initial base discharge at each channel is computed using an assumed suitable rainfall intensity and Rational method. The initial depth of this model involves downstream boundary condition effect and is derived from downstream end using Standard-Step Method. The inflow of each manhole is computed by Horton’s overland flow hydrological model or given measured field data. We regard manholes of this system as the internal condition and simulate them with conservation of mass and condition of water stage. A water stage or free fall condition is specified at the downstream boundary. The model is capable of simulating flow conditions such as open channel flow for dividing channel, junction channel and loop-reach, pressure flow and drowned flow drainage system. We choose rectangular shape and circular shape to simulate and use several kinds of symmetrically allocated tube network to evaluate. The results are in good agreement with physical phenomena.
