内镶式滴灌管主流道水流运动特性研究  

HYDRAULIC PERFORMANCES IN MAINSTREAM OF DRIP IRRIGATION PIPE

作　　者：丁法龙 茅泽育[1] 韩凯 DONG Fa-long;MAO Ze-yu;HAN Kai(Department of Hydraulic Engineering,Tsinghua University,Beijing 100084,China)

机构地区：[1]清华大学水利水电工程系

出　　处：《工程力学》2019年第11期248-256,共9页Engineering Mechanics

基　　金：国家重点研发项目(2016YFC0402504)

摘　　要：以质量和动量守恒定理为依据,建立了以内镶式滴灌管为例的多孔管流动数学模型,并结合水力试验数据,推导得出了内镶式滴灌管内部主流道的沿程压力分布模型。多孔管流动的数学模型表明:多孔管主流道内的压力大小及变化取决于摩阻作用和动量交换作用的相对大小,其中摩阻作用使得压力降低,动量交换作用使压力升高,多孔管压力分布模型可以归结为求解管路摩阻系数和动量交换系数。滴灌管水力试验表明:滴灌管沿程纵向流速的分布指数与滴头自身特性(流量系数、流态指数)无关,而与管路上的滴头个数呈良好的线性相关关系。以水力试验数据分析与理论推导为基础,得出动量交换系所对应的经验表达式,结合BLASIUS摩阻系数计算公式对滴灌管压力分布模型进行求解,模型预测值与实测值吻合良好。该压力分布模型中,将沿程压力分布的影响因素归结为滴灌管长径比和管首雷诺数,便于优化结构设计及确定最佳运行工况。该文可为多孔管路水力计算及变质量流动模型研究提供一定参考。Based on the theorem of mass and momentum conservation, this study established an analytical model for variable mass flow, and thusly developed a mathematical expression for the longitudinal pressure distribution along the mainstream of a drip irrigation pipe combined with experimental data. The established model shows that the longitudinal pressure distribution in the drip irrigation pipe is dependent on friction head loss and momentum exchange, and that friction head loss tends to decrease the pressure and the momentum exchange tends to increase it. The solution of the longitudinal pressure distribution model is attributed to determining friction and momentum exchange coefficients. The test results show that distribution index of longitudinal velocity is independent of the characteristic parameters of the drip irrigation pipe, but linear with the number of drip emitters. The expression for the momentum exchange coefficient was obtained by theoretical derivation and regression analysis, and the friction coefficient can be calculated by Blasius formula. The analytical model for variable mass flow and the longitudinal pressure expression for the drip irrigation pipe was then solved. The calculated values of the longitudinal pressure along the drip irrigation pipe agreed well with measured values. In the longitudinal pressure expression, pressure is affected by a pipe-structure parameter(length-diameter ratio)and a flow parameter(entrance Reynolds number). The expression helps guide the structural design and optimize operating conditions, because the two parameters are both directly controllable. This study offers a new thought for the analysis of variable mass flow, and the results would provide a scientific basis for the hydraulic calculation of drip irrigation.

关 键 词：滴灌管 主流道 变质量流动 摩阻 动量交换 沿程压力分布 

分 类 号：S275.6[农业科学—农业水土工程]