Experimental study on effects of vegetation roughness on flow resistance of open channel
-
摘要: 以水力半径分割法的思想为出发点,建立了新的明渠阻力分割计算关系式,在此基础上分析研究明渠中处于淹没状态下床面柔性植物对水流阻力的影响。采用多普勒流速仪测量边壁附近的流速,用间接法中的流速测量法测量边界上的切应力,用棕榈毛作为植物的模拟材料。以植物粗糙度表示植物阻力,用植物高度、密度的函数表示床面粗糙度,在植物高度和密度变化的情况下,进行水槽试验。经过对试验数据分析,发现植物粗糙度随植物高度、密度的增加而增加,且植物粗糙度越大时,在数值上越接近植物高度。拟合粗糙度与植物高度和密度的经验关系式,进而得出了植物阻力的计算式。Abstract: Based on the thought of hydraulic radius separated method,a new computation formula for open-channel resistance segment is created. The influence on flow resistance of flexible vegetation,which is submerged on bed surface of the open channel,is explored and analyzed. A three-dimensional-acoustic Doppler velocimeter is used to measure the velocity near the wall. Measurement of velocity in indirect method is used to determine the tangential stress on the wall. The hair of palm is used to imitate the vegetation. Under the condition of different heights and densities,a series of flume experiments are carried out. The vegetation roughness is used to express the vegetation resistance and the vegetation height and density is used to express the roughness of bed surface. By the regression analysis to experimental dates,the conclusion is that the vegetation roughness increases along with the increase of the vegetation height and density;the bigger the roughness of the vegetation,the more approximate to the vegetation height its numerical value. Empirical relationships between them are fitted and then the computation formula of vegetation resistance is derived.
-
Key words:
- open channel flow /
- vegetation /
- resistance of bed /
- roughness /
- experimental study
-
[1] LI R M,SHEN H W.Effect of tall vegetation on flow and sediment[J].J Hydr Div,1973,99(5):793-814. [2] FREEMAN G E,RABMEYER W H,COPELAND R R.Determination of resistance due to shrubs and woody vegetation[R].Vicksburg,MS:Technical Report ERDC/CHL TR-00-25 U S.Army Engineer Research and Development Center,2000.15-28. [3] URSULA S,KARL W.Experiments on hydraulic roughnesss of macrophytes[A].Proceeding of Theme B XXIX IAHR Congress[C].Beijing:2001.358-364. [4] CAROLLO F G,FERRO V,TERMINI D.Flow resistance law in channels with flexible submerged vegetation[J].J Hydr Engrg,2005,131(7):554-564. [5] JARVELA J.Affect of submerged flexible vegetation on flow structure and resistance[J].Journal of Hydrology,2005,307(1-4):233-241. [6] NEHAL L,YAN Z M,XIA J H.Study of the flow through non-submerged vegetation[J].Journal of Hydrodynamics,2005,17(4):498-502. [7] MUSLEH F A,CRUISE J F.Functional relationships of resistance in wide flood plains with rigid unsubmerged vegetation[J].J Hydr Engrg,2006,132(2):163-171. [8] GREEN J C.Effect of macrophyte spatial variability on channel resistance[J].Advances in Water Resources,2006,29(3):426-438. [9] EINSTEIN H A.The bed load function for sediment transportation in open channel flow[M].U S Dept Agri Tech Bull,1950.1026. [10] 胡春宏,吉祖稳.论明渠水流边界剪应力分布规律[A].第二届全国泥沙基本理论研究学术讨论会论文集[C].北京:中国建筑工业出版社,1995.85-93.(HU C H,JI Z W.The law of boundary shear stress in open channels[A].Second national academic symposium of basic theory study on sediment[C].Beijing:Chinese Building Industry Press,1995.85-93.(In Chinese)) -

计量
- 文章访问数: 160
- HTML全文浏览量: 23
- PDF下载量: 613
- 被引次数: 0