Experimental Study to Evaluate the Effectiveness of the Variation in Crown Portion of a Tree on the Flow Properties Considering the Finite Length Forest
Experimental Study to Evaluate the Effectiveness of the Variation in Crown Portion of a Tree on the Flow Properties Considering the Finite Length Forest
复制标题
考虑有限长度森林的树冠部分变化对流动特性有效性评估的实验研究
DOI：
10.1007/s40999-022-00759-4
复制
发表时间：
2022
影响因子：
1.7
通讯作者：
N.
中科院分区：
文献类型：
--
作者：
Amina;Tanaka;N.
This study clarified the effects of changing the ratio of the tree crown part to tree height in an inland finite length coastal forest under fixed bed conditions with special emphasis on the reduction of energy, velocity, and fluid force behind the forest and the difference in velocity between the forest and an adjacent gap region. A series of tests were conducted under sub-critical flow circumstances while altering different variables such as the crown height ratio (where \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C^{\prime}_{h} = {\raise0.7ex\hbox{${C_{h} }$} \!\mathord{\left/ {\vphantom {{C_{h} } {T_{h} }}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{${T_{h} }$}}$$\end{document} in whichis the crown distance from the ground surface andis the tree height), forest width-to-length ratiowhereandis cross-stream length (width) and stream-wise length of a forest, named FM-1 and FM-2, respectively), and the initial Froude number condition \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left( {Fr_{o} } \right)$$\end{document}, which ranged between 0.67 and 0.76. The results showed that an FM-2 case with the lowest tree crown height (created a significant backwater rise, accompanied by a higher flow resistance than an FM-1 configuration. The maximum energy loss, around 67%, was observed with the lowest tree crown in an FM-2 case as compared to no-crown and high-crown models. This forest configuration reduced the flow velocity and fluid force behind the forest by around 50% and 59%, respectively. On the other hand, flow velocity in FM-1 with lower crown height ratios increased only approximately (3–4%) compared to the no-crown (NC) case. However, the energy loss was only 50% in the FM-1 case with the lowest crown height ratio, whereas FM-2 had a negative impact on the gap area due to a linear increase in flow velocity, and velocity increased from (around 44–69% as compared to the NC case (18%). The best reductions of the oncoming current energy, velocity, and fluid force behind the forest were seen when the FM crown height ratio was reduced, and its width-to-length ratio was increased. This design of an inland forest as a natural bioshield would reduce the potential damage by future tsunami disasters.
This study clarified the effects of changing the ratio of the tree crown part to tree height in an inland finite length coastal forest under fixed bed conditions with special emphasis on the reduction of energy, velocity, and fluid force behind the forest and the difference in velocity between the forest and an adjacent gap region. A series of tests were conducted under sub-critical flow circumstances while altering different variables such as the crown height ratio (where \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C^{\prime}_{h} = {\raise0.7ex\hbox{${C_{h} }$} \!\mathord{\left/ {\vphantom {{C_{h} } {T_{h} }}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{${T_{h} }$}}$$\end{document} in whichis the crown distance from the ground surface andis the tree height), forest width-to-length ratiowhereandis cross-stream length (width) and stream-wise length of a forest, named FM-1 and FM-2, respectively), and the initial Froude number condition \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left( {Fr_{o} } \right)$$\end{document}, which ranged between 0.67 and 0.76. The results showed that an FM-2 case with the lowest tree crown height (created a significant backwater rise, accompanied by a higher flow resistance than an FM-1 configuration. The maximum energy loss, around 67%, was observed with the lowest tree crown in an FM-2 case as compared to no-crown and high-crown models. This forest configuration reduced the flow velocity and fluid force behind the forest by around 50% and 59%, respectively. On the other hand, flow velocity in FM-1 with lower crown height ratios increased only approximately (3–4%) compared to the no-crown (NC) case. However, the energy loss was only 50% in the FM-1 case with the lowest crown height ratio, whereas FM-2 had a negative impact on the gap area due to a linear increase in flow velocity, and velocity increased from (around 44–69% as compared to the NC case (18%). The best reductions of the oncoming current energy, velocity, and fluid force behind the forest were seen when the FM crown height ratio was reduced, and its width-to-length ratio was increased. This design of an inland forest as a natural bioshield would reduce the potential damage by future tsunami disasters.
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