خصوصیات هیدرولیکی جریان پر پیچ و خم در مسیر ساتع کننده آبیاری قطره ای

At present, the tortuous emitter has the most advanced performances in drip irrigation. But the theories and methods for designing its flow path have been strictly confidential and the researches on the function of practical guidance have seldom been published. Seven types of most representative tortuous emitting-pipes currently used in agricultural irrigation regions of China were chosen for investigating the geometric parameters of the flow path by means of combining high-precision microscope and AutoCAD technology. By the measurement platform developed by the authors for hydraulic performances of emitters, the free discharge rates from the 7 types of emitters were measured at 9 pressure levels of 1.5 m, 3.0 m, 5.0 m, 7.0 m, 9.0 m, 10.0 m, 11.0 m, 13.0 m and 15.0 m. Then the discharge-pressure relationship, manufacturing variation coefficient, average velocity on the cross-section of flow path and the critical Reynolds number for the flow regime transformation within the paths were analyzed in detail. The results show that both pressure-ascending work pattern and pressure-descending work pattern have some impacts on the discharge rates of tortuous emitters, but the impact level is not significant. The target pressure could be approached by repetitive applications of the two work patterns during pressure regulation. The operation under low pressures has some impacts on the hydraulic performances of emitters, but the impact level is also not significant. The classical model of the discharge-pressure relationship is suitable for the pressure range of 1.5 m–15.0 m. The Reynolds number for fluids within the 7 types of tortuous emitters ranges from Re =105 to Re =930. The critical Reynolds number for the flow regime transformation is smaller than that for the routine dimension flow path. The variation coefficient of emitter discharge rates is slightly fluctuating around a certain value within the whole pressure range.

The tortuous drip irrigation emitter is the emitter with most advanced hydraulic performances. In this study the hyd raulic performances of tortuous drip irrigation emitters and the flow characteristics within the flow paths have been researched. It is concluded that both pressure-ascending work pattern and pressure-descending work pattern have some impacts on the discharge rates of emitters, but the impact level is not significant. The hydraulic performances of the tortuous path emitters were affected under the low-pressure range, but the classical model for the discharge-pressure relationship is suitable for the pressure range of 1.5 m-15.0 m. The Reynolds number for the fluid in the 7 tortuous paths of emitters was =105-930, and the critical Reynolds number for the flow regime transition are smaller than that for the routine-dimension flow path. Re Further researches need the application of the velocity measurement technology with Micro-PIV graphs to simulate the internal fluid field within the paths [22]