【作者】 雷显龙；

【导师】 杨培岭；

【作者基本信息】 中国农业大学 ， 农业水土工程， 2001， 硕士

【摘要】 滴灌是缓解水资源紧缺状况和改善农业生产条件的有效方法。然而，滴头流道边界复杂，给研究其中的水流流态带来很大的困难，水流在流道中的消能机理不明确，严重地制约了滴灌设备的发展。分形理论为研究复杂的非线性现象提供了强有力的手段，利用它不但能描述复杂的不规则现象，而且还可以构造非线性的几何体，为滴头内水流的研究和滴头流道的设计提供了新的方法。 本文通过对迷宫流道滴头的消能方式的分析，提出用分形理论构造分形体作为流道边界的方法。设计了八种不同的平面流道，并用点火花切割方法加工了流道样品。测定了各种流道在五种不同压力下的流量压力参数，研究在分形流道内物理尺寸对滴头消能能力的影响。结果表明，所设计的流道比常规的迷宫式流道具有更强的消能效果，其流态指数可以小到0.33，常规的迷宫流道滴头流态指数通常都在0.35以上，分形流道具有降低滴头的压力敏感的能力。 本文对分形流道内的流态进行了初步研究，结果表明流道的不规则边界所引起的局部水头损失是流道的主要消能因素。建立了以流道齿的高度（H）和流道深度（D）的比值作为流道局部水头损失的主要影响因素的函数关系，计算分形流道的局部水头损失系数，并对所设计的流道的流量压力进行对比，计算值和实测值相差-18—16％，可以为设计滴头流道的参考。更多还原

【Abstract】 Tickle irrigation is one of the most important measures to reduce the water resources shortage challenging and to develop the agricultural condition. However, the development of emitters was restricted for the complicated flow in the path of emitters, which was difficult to be mastered. Fortunately, the creation of Fractal Theory has offered a strong technique to describe nonlinear and to construct phenomenon. In this work, flow paths were designed based on the Fractal Theory to explore its capability to diminish pressure head. The basic flow and pressure parameters in the path were studied to determine the effect of the flow path on the pressure losses. 8 emitters were designed and tested to determine flow rates at five different pressures. Flow path dimensions, and pressures values were used to determine expected flow rates using the modified Darcy equation. Results showed that the equation severely overestimated the flow rates. Head losses are caused by means of sharp bends and turns. A model was developed to find the effect of bends on the pressure losses in fractal path emitters. The model developed successfully predicted head flow rate. The differences between predicted and actual head loss for most emitters were between ?8% and 16%. It was shown that the flow path could be designed on the ratio of height of bend to the depth of path (HID).更多还原