煙流上升高度係決定地面濃度值重要參數之一，於簡單狀況下，煙流上升可用經驗式或積分模式來決定之。但於較複雜之流場；如多煙囪等，這些方法卻不甚適合，過去於較複雜煙流之模擬大多以風洞實驗來進行。本研究以現有三維數值模式直接解控制方程式來模擬煙流於大氣邊界層中之行為，此計算機模式係直角坐標有限元素法，於考慮浮力效應(Buoyancy effect)，以時間平均法則滿足動量、能量、及質量守恆方程式，並考慮亂流效應，以k-ε亂流閉合模式來模擬。於中性穩定下模擬結果，當煙囪排列成一直線與風向平行時，煙流提升效應最大，其提升係數界於Briggs與Overcamp研究結果之間；當煙囪排列成一直線與風向垂直時，提升效應最小，另外模擬三煙囪正三角形排列下其煙流上升比直線排列為大，由以上不同排列之多煙囪煙流模擬結果得知，煙流上升比前人之研究其適用範圍更廣泛，顯示本數值模式非常適合於大氣邊界層中煙流上升之研究。此外數值模擬結果可瞭解煙流運行之細節，例如煙流分岔之發生，這些是其他解析方法所不易達到的。 Plume rise is an important parameter for determining the ground level concentration. For simple situation, the rise of a plume can be determined either by empirical formulas or simple integral models that employ entrainment assumption. However, these approaches are not suitable for complicated flow, Such as the plume rise of multiple sources, which are usually investigated by wind tunnel experiments. In this study, a numerical method was used to study plume rise. The governing equations, including the conservation equation of mass, momentum, energy, and pollutant mass, were solved by a finite element code to obtain the three-dimensional velocity and concentration fields. The turbulent closure model is the standard k-ε model. The effects of effluent and atmospheric conditions on the behavior of plume were considered, and different stacks arrangements were modeled. When compared with Overcamps’ and Briggs’ experimental studies, the results from this study were more satisfactory.
