蜿蜒渠流受側入流影響之探討

Abstract

天然河川多為蜿蜒且常有主支流交匯，其水理及泥砂運動形態複雜，為易發生災害之處。主渠與支渠於水流匯合處之動量傳遞常造成流況急劇變化，若主流為蜿蜒渠道，流況將越顯複雜，進而影響河道輸砂能力，甚至造成河工結構物發生破壞。因此，本研究針對蜿蜒河道受側入流匯入所造成之流場變化做進一步的分析與探討。 本研究進行蜿蜒渠槽匯流試驗與蜿蜒渠槽單槽試驗，以二維電磁式流速儀量測交匯處下游各斷面之流場流速，由試驗所得資料驗證三維模式RESED3D之模擬結果，比對結果良好，顯示數值模式在模擬交匯流場及連續彎道上之發展具合理性及可靠性。本研究並由比較蜿蜒渠槽有無受側入流匯入影響之斷面流速分佈以及斷面水深分佈等，探討蜿蜒渠流受側入流匯入影響之流場變化。

Natural rivers with meanders and confluences have complicated patterns of flows and sediment transport behaviors, in which disasters may be frequently induced. In junction regions between main stream and branches, momentum transitions often cause dramatic changes in flow conditions and getting more severe with higher levels of meandering. And therefore, by following that the instability of bed evolution induced by the dramatic change of sediment movement may inflict the severe damage on the flood-proof infrastuctures. The main purpose of this study is to investigate the changes of flow characteristics in a meaderning channel with the introduction of lateral flows. Experiments were conducted to investigate the flow behaviors in junctions and along channels. Velocity measurements were taken using an acoustic doppler velocimeter over a gridded junction region. The simulation results of a 3D model (RESED3D) showed well agreement with the experimental data. Furthermore, this study investigates the differences in velocity distribution and water depth distribution between the meandering channels with and without lateral flows.