Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/89395
標題: Flow Field and Fluvial Bed of Different Bent Plants Distribution under Sediment Supply
上游來砂條件下倒伏植株分佈對流場及沖積河床之探討
作者: 李津甫
Jin-Fu Li
關鍵字: 倒伏植株
流場變化
沖積河床
隨機分佈
bent plant
flow field
fluvial bed
random distribution
引用: 1. Ackerman, J. D. and Okubo, A. (1993). 'Reduced mixing in a marine macrophyte canopy,' Functional. Ecology, 7, 305-309. 2. Chen, S. C., Kuo, Y. M. and Li, Y. H. (2011). 'Flow characteristics within different configurations of submerged flexible vegetation,' Journal of Hydrology, 398, 124–134. 3. Chen Su-Chin, Hsun-Chuan Chan, Yu-Hsiu Li, (2012), 'Observations on flow and local scour around submerged flexible vegetation', Advances in Water Resources, 43, 28-37 4. Elizabeth M. Follett and Heidi M. Nepf, (2012), 'Sediment patterns near a model patch of reedy emergent vegetation', Geomorphology, 179, 141-151 5. Ghisalberti, M. and Nepf, H. M. (2002). 'Mixing layers and coherent structures in vegetated aquatic flows,' Journal of Geophysical Research, 107, NO. C2, 10.1029/2001JC000871. 6. Green, J. C. (2004). 'Modeling flow resistance in vegetated streams: review and development of new theory,' Hydrological Processes, 19, 6, 1245-1259. 7. Kouwen N. and Unny, T. E. (1973). 'Flexible roughness in open channels,' Journal of the Hydraulics Division, 99, 5, 713-728. 8. Kouwen, N. and Li, R. M. (1980). 'Biomechanics of vegetative channel linings,' Journal of the Hydraulics Division, 106, 6, 1085-1103. 9. Raudkivi A. J. and Ettema R., 1983, 'Clear-water scour at cylindrical piers,' Journal of Hydraulic Engineering., ASCE, 109(3): 338-349. 10. Sand-Jensen, K. (2003). 'Drag and reconfiguration of freshwater macrophytes,' Freshwater Biology, 48, 271-283. 11. Sezaki, T., Hattori, A., Kondo, K., Tokuda, M., Fujita, K., and Yoshida, M., (2000). 'Field study on the destruction processes of herbaceous vegetation on gravel bars due to flood flows,' Annual Journal of Hydraulic Engineering, 44, 825-830. 12. Sugio, S. Watanabe, K. and Tanoue A. (2003). 'Research on the destruction of herbaceous vegetation by flood flow on sand bar in recovering process,' Annual Journal of Hydraulic Engineering, 47, 1003-1008. 13. Sugio, S. and Watanabe, K. (2004). 'Destruction of herbaceous vegetation by flood flow on a floodplain in a recovery process,' Proceedings of River Flow 2004, 1315-1323. 14. Tsujimoto, T., Kitamura, T., Fujii, Y. and Nakagawa, H. (1996). 'Hydraulic resistance of flow with flexible vegetation in open channel,' Journal of Hydroscience and Hydraulic Engineering, 14, 1, 47-56. 15. 嚴曉嘉 (2007),「植生擺設型態對水流與床砂變化之渠槽實驗」,國立中興大學水土保持學系研究所碩士論文,碩士論文。 16. 李育修 (2008),「渠槽植株排列對泥沙沖淤及流況影響之研究」,國立中興大學水土保持學系研究所,碩士論文。 17. 許懿尹 (2012),「單株倒伏植株水理型態與沖刷特性之試驗研究」,國立中興大學水土保持學系研究所,碩士論文。 18. 廖哲緯 (2013),「倒伏植株葉片長短對於流場及底床沖淤型態之影響」,國立中興大學水土保持學系研究所,碩士論文。 19. 陳葉宏 (2015),「倒伏植株群的疏密型態對於水理機制與沖淤特性影響之探討」,國立中興大學水土保持學系研究所,碩士論文。
摘要: 由於近年來氣候變遷程度日益嚴重,使得極端降雨發生的頻率增加,造成河川洪水災害發生次數及規模皆有增加之趨勢,當洪水漫淹沙洲、邊灘以及高灘地上之植生群落時,其水、砂對植物之植株與根系所產生之交互作用,將會影響河道中床型演變的過程。本研究以柔性塑膠材質模擬當植物遭遇洪水時,植株本體受水流衝擊而自然倒伏後對整個河道流場剖面之影響;並將流速設定為大於啟動流速且在上游持續加砂的條件下,觀察植株在洪水來臨時對沖積河床之影響。 本試驗使用3種不同植株密度,每種植株密度以隨機排列方式再分成3種不同排列型態,共9次水槽試驗。試驗中以超音波流速剖面儀(UVP)量測整個流場剖面,並以縮時攝影機拍攝床型變化歷程,試驗後以影像式雷射掃描儀(Mantis vision's F5)測量床型變化結果。 試驗結果可分為流場變化與地形沖淤2個部分來表示。在流場變化部分,水流紊動的強度與植株密度是呈正相關的,首先受到植生影響的是位於下層的水流,隨著植生密度的逐漸增加,受植生所影響的水流高度也會逐漸提高。當植生達一定密度時,植生區前的流速剖面會呈鋸齒狀的變化,流速增加及減少之極值所發生的位置也會隨植生密度增加而提高,而流速變化的幅度也與植生的密度呈正相關。在地形沖淤的部分,隨著植株密度的上升,底床要達到動態平衡所需的時間也越久。比較植生區上游及下游面的床型變化量,植生區上游面的堆積量與植生密度是呈正相關的,而植生區下游面的淘刷量與植生密度是呈負相關的,因此可推斷在洪水來臨時灘地植生的確具有保護底床的功能,但其密度需大到超過一臨界值,否則植生對底床所造成的效果還是以負面效果較大。
It was due to the extent of climate change increasingly severe that the frequency of extreme rainfall occurs increased in recent years. It caused an increase in times and scale of the trend river flood disaster. While the flood swept the plant community on the sandbar and floodplain , the fluvial bed arose the interaction with the water, sand and plants. It will affect the fluvial bed type process of evolution. In this study, the flexible plastic material were used to simulate the plant community when they were bent by the current rush. To observe the impact on all flow field of the bent plants. And the flow velocity was set at greater than critical velocity and supplied the sediment in the upstream. To observe the impact on fluvial bed of the bent plants. This experiment used three different plant densities, each density subdivided into three different random arrangement patterns, a total of nine times flume experiment. The experiment used Ultrasound Velocity Profiler (UVP) to measure flow field and used camera to film bed type change course. After the experiment, used laser scanner (Mantis vision's F5) to measure the result of fluvial bed change. The experimental results can be divided into flow field and topography two parts to represent. In the flow field portion, turbulence intensity and plant density are positively correlated. The lower current was affected by plants earliest, along with increasing density of plants, the affected height of the current will gradually raise. When the plant density reaches a value, the flow field profile before planting area will changes to jagged. Along with increasing density of plants, the location of extreme value of velocity change will gradually raise. The velocity magnitude of change also showed positively correlated with plant density. In the topography portion, along with increasing density of plants, the fluvial bed need longer time to achieve the dynamic balance. Then we compared with the volume of upstream bed change and downstream bed change. The deposit volume before the planting area and plant density are positively correlated, but the scour volume after the planting area and plant density are negatively correlated. Therefore we can infer plants have the effect to protect the riverbed. But the plant density must higher than critical value. Otherwise the effect on scour is larger than deposit on the riverbed.
URI: http://hdl.handle.net/11455/89395
其他識別: U0005-0408201515333100
文章公開時間: 2018-08-07
Appears in Collections:水土保持學系

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