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標題: Experimental Study on Flows Induced Scour around Emergent Vegetation Zone with Different Densities
作者: Chan, Hsun-Chuan
Huang, Yin-Tzu
Jhih -Syong Peng
關鍵字: Experiments;Flows;Vegetation;Scour;實驗;水流;植生;沖刷
Project: 水土保持學報, Volume 48, Issue 4, Page(s) 1877-1894.
In the natural rivers, woody vegetation commonly grows along the riverbank. When flows run through the vegetation zones, the stream processes are markedly affected. This study experimentally investigated the flows induced scour around the vegetation zone with different densities. Since vegetation grows along the nature bank, the model vegetation was arranged along one side of the experimental flume. The experiments were expected to simulate the near bank scour in the jointed effects of vegetation and flow. Model vegetation was simulated by the steel columns in the emergent flow conditions. The experimental flow was steady and flow velocity and was adopted to close to the initiation of sediment motion. The bed morphology of equilibrium scour condition was measured by a Laser Distance Meter in the cases of vegetation density equal to 0.03, 0.04, 0.05, 0.07, 0.09, 0.12, 0.15, 0.22, and 0.3. The results showed, while the vegetation density ranging from 0.03 to 0.12, the dimensionless characteristic length D ranges between 1.30~1.50; the dimensionless characteristic length A ranges between 0.94~1.27; the dimensionless characteristic length B ranges between 1.11~1.48; the dimensionless characteristic length C ranges between 1.05~1.42; the dimensionless characteristic length E ranges between 1.18~1.67 and; the dimensionless characteristic length F ranges between 0.49~1.81. It was also showed the dimensionless characteristic lengths A, B C, D, and E are high-positive correlation to the vegetation density respectively. Moreover, the flows induced scour around the vegetation zone extended to the main channel while the vegetation density ranging from 0.15 to 0.3.

天然河道常存在河濱植生,植生若生長茂密將阻礙水流致使通水面積減小,進而造成底床 型態產生變化,底床之沖刷與淤積改變會影響河道的穩定性,因此河濱植生之密度對河床沖淤 之影響為水力學中重要之議題。本研究以室內渠槽試驗探討高莖植物在高灘地存在對附近河床 沖淤的影響,比較不同密度模型植生之底床沖淤影響差異。考量河濱植物通常生長於河岸,試 驗過程將植生佈置於試驗渠槽之單側邊壁,試驗入口流速趨近試驗泥砂之啟動流速,以雷射測 距儀量測平衡型態之底床沖淤變化。試驗植生密度設計為 0.03、0.04、0.05、0.07、0.09、0.12、 0.15、0.22 及 0.3,另進行剛性不透水試驗組做為參考比較對象。分析結果顯示密度 0.03 到 0.12 時,無因次化的沖刷坑特徵長度 D 變化範圍介於 1.30-1.50 間,無因次化的沖刷坑特徵長 度 A 變化範圍介於 0.94-1.27 間,無因次化的沖刷坑特徵長度 B 變化範圍介於 1.11-1.48 間, 無因次化的沖刷坑特徵長度 C 變化範圍介於 1.05-1.42 間,無因次化的堆積丘的寬度 E 變化範 圍介於 1.18-1.67 間,無因次化的堆積丘特徵長度 F 變化範圍介於 0.49-1.81 間,特徵長度 A、 B、C、D 及 E 具有高度線性相關;密度 0.15 到 0.3 沖刷和堆積型態類似於不透水模型墩柱,沖 刷坑由墩柱正前方向渠道中心側沖刷,受邊壁影響呈現半馬蹄形沖刷坑,堆積都是從沖刷坑要 結束處開始形成。
Appears in Collections:第48卷 第04期

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