植物粗糙度对明渠水流阻力影响的试验研究

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。

Experimental study on effects of vegetation roughness on flow resistance of open channel

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.