【作者】 潘志宝；

【导师】 吕宏兴；

【作者基本信息】 西北农林科技大学 ， 水利水电工程， 2009， 博士

【摘要】 渠道量水是灌溉用水管理的基本条件,是一项基础且关键性的技术,对灌区节水、实现水资源高效可持续利用具有重要意义。研究具有结构简单、操作简便、水头损失小、量水精度高、流量计算公式简明的渠道量水设备,是灌区迫切需要的灌溉管理实用技术之一。由于灌区条件比较复杂,很难应用统一的量水设施,目前已有的槽类量水设施还不能满足灌区量水的要求。因此研究开发适合我国灌区目前经济发展状况以及能满足特定量水要求的量水设施和测流技术是当前灌区量水研究的着眼点。特别是针对末级渠系只中面广量大的斗、农渠以及缓坡渠道量水设施的研究,应是目前研究工作的重点方向。具有流线形特征的机翼形量水槽结构简单、过流平顺、流态稳定,可作为新型的量水结构加以研究。本文在初步研究的基础上,按照理论分析、试验研究、数值计算与灌区现场实验相结合的研究思路和方法,对机翼形量水槽的各项水力特性进行了深入系统的研究与分析。主要研究内容与结论如下：1、总结了灌区量水技术与设施特别是量水槽的最新发展,详细阐述了临界水深类量水槽的测流原理。并采用量纲分析法及传统水力学基础理论分别推导U形渠道、矩形渠道、梯形渠道机翼形量水槽过流的水位流量关系,得出了流量计算公式,并加以试验验证。结果表明,采用两种方法得到的流量计算公式简明实用,测流精度都符合量水规范对灌区量水设施的要求。2、以矩形渠道机翼形量水槽为例,对过槽水流从流态上进行了定性的讨论和总结,为深入理解流经机翼形量水槽等短喉道类量水槽的水流流态提供参考依据,并以期指导量水槽设计。对于水平渠道机翼形量水槽而言,在理想状态下临界流发生在渠道侧向收缩达到极小值的断面,即喉口断面。通过一定的工程措施促使量水槽断面收缩比从大到小变化,则过槽水流便可依次呈现出缓流、临界流、急流三种流态。只要控制量水槽内的水流为急流,就可以获得较高的临界淹没度。3、通过室内试验研究了三种渠道机翼形量水槽的各项水力特性,包括临界淹没度、壅水高度及上游断面佛汝德数,为量水槽在灌区应用提供技术参数。U形渠道、矩形渠道、梯形渠道机翼形量水槽的临界淹没度都较高,因此在平原灌区,也可保证量水槽上游水位在大范围内不易受下游水位的影响。与其他两种渠道机翼形量水槽相比,矩形渠道机翼形量水槽的上游水面波动一般很小,流速分布比较均匀,槽前佛汝德数也相对较小。试验得到的机翼形量水槽在各种渠道中的壅水高度都能满足灌区要求。4、分析了机翼形量水槽过流水头损失的机理及影响因素。量水槽过槽水流水头损失包括槽前收缩段、下游扩散段以及从扩散段到槽后一定距离内的水跃段水头损失三部分。将过槽水头损失全部看作局部水头损失,经数据分析得到局部水头损失系数与过槽流量、断面收缩比以及淹没度的关系。U形渠道、梯形渠道机翼形量水槽的水头损失系数变化规律类似,但与矩形渠道机翼形量水槽的明显不同。5、研究了数值计算中网格大小、湍流模型对数值模拟结果的影响,为后续数值模拟选定了合理的模拟参数及数学模型。以U形渠道机翼形量水槽为例对量水槽三维水流运动进行了数值计算。重点关注在自由出流时,不同收缩比及流量下水面线的变化,再现过槽水流流线及速度场,以及在下游水位得到控制时的量水槽淹没度。通过非稳态数值计算,得出量水槽过流过程及水位的瞬态变化。对比验证计算与试验,结果表明：采用CFD模拟技术可以较好地模拟量水槽三维水流现象。在此基础上对物理试验模型之外的机翼形量水槽过流进行了预测模拟,从而突破物理模型在尺寸及研究范围上的限制,进一步拓宽了量水槽研究的范围。6、分别在内蒙古鄂尔多斯黄河南岸灌区和引大入秦输水干渠上进行了U形渠道与矩形渠道机翼形量水槽的应用实验研究。结果证明,机翼形量水槽水头损失小,临界淹没度高,便于施工。总结了机翼形量水槽在灌区应用中包括设计、修建及率定等各个环节的实践经验,并为机翼形量水槽在灌区的大范围推广给出了合理建议。通过对机翼形量水槽在三种渠道上的试验以及现场实验研究表明,机翼形量水槽可以代表灌区量水槽新的发展方向,有较好的推广价值和应用前景。更多还原

【Abstract】 Water gauging in canals is a foundation of the water management and a critical technique. It is of great significance for water saving and water utilization in irrigation districts efficiently and sustainably. Studying the water measuring facility with simple structure, easy operation, low head loss, high accuracy and clear discharge formula is one of the irrigation management techniques urgently needed in irrigation districts. Because of the complicated conditions in the irrigation districts, it is difficult to apply a uniform water measuring facility. At present, water-measuring flumes cannot fulfill the demand of water gauging in irrigation districts. Developing water measuring facility and technique suited to current economic development level and specific requirements to meet the water-gauging demand, therefore, is the springboard of the research, especially for a large number of sublateral and farm canals and gentle slope canals. The streamlined Airfoil-shaped measuring flume, which is characterized by its simple structure and smooth flow, can be studied as a new water-measuring device. According to indoor experiments in accordance with theoretical analysis, numerical calculations and irrigation field tests, hydraulic characteristics of Airfoil-shaped measuring flume are studied systemically based on the preliminary studies.1. This article summarizes the facility and technique of water gauging in irrigation districts including the latest developments of water measuring flume, and describes the water-gauging principle of critical water-depth flume in details. It also obtains discharge formula by the method of dimensional analysis and traditional hydraulics in the U-shaped, rectangular and trapezoidal canal and compares it with the experiment data. Simple, clear and practical discharge formula obtained by the two methods can meet the demand of the accuracy requirement.2. This article, taking the Airfoil-shaped measuring flume that used in rectangular canal for example, qualitatively discusses and summarizes flow pattern of flow passing through the flume. It provides theoretical basis to understand short-throat flume’s flow pattern and guides the design of the water-measuring flume. As for the Airfoil-shaped measuring flume built in the even canal, the critical flow occurs at the throat inlet cross section, which has the minimum local contraction. Certain engineering measures can be taken to make the cross section’s ratio of local contraction changed from big to small values, then the flow in the flume can present a sub-critical, critical or super-critical flow patterns successively. Provided that flow in the water measuring flume can be controlled to be a super-critical flow, a high critical submergence will be obtained.3. The laboratory tests on various water measuring characteristics of the Airfoil-shaped measuring flume built in the three different canals are conducted. Critical submergence, backwater height and Froude number of the upstream cross section are analyzed to provide technical parameters for the application of water measuring flume in the irrigation districts. The critical submergence of the Airfoil-shaped measuring flume built in the three different canals is high enough so that the flume can work under free flow condition over a considerable extent even in the plain irrigation districts. Compared with the others, the upstream water of Airfoil-shaped measuring flume built in the rectangular canal is fluctuant more smoothly Meanwhile velocity distribution is more evenly and upstream Froude number is small relatively. The backwater heights obtained among the laboratory tests can fulfill the demand of the irrigation districts.4. This article analyzes the mechanism and effect factors of the head loss of the flow passing through the Airfoil-shaped measuring flume. The head loss includes losses of the contraction section in the upstream、expansion section in the downstream and the hydraulic jump section. The total head loss can be taken as local head loss. The relation between the local head loss coefficient and the discharge, cross section contraction ratio and submergence is obtained by the data analysis. The change laws of head loss coefficient of Airfoil-shaped measuring flume in the U-shaped and trapezoidal canals are similar, but significant different from that of flume in rectangular canal.5. A serial of calculations also are performed on how the meshes, turbulence models influence the numerical simulation. It provides reasonable simulation parameters and mathematic models for the later numerical simulations. The 3D water flow numerical calculations are carried out on the Airfoil-shaped measuring flume in the U-shaped canal. It mainly focuses on the change of water surface curves, streamlines, velocity field and submergence which controlled by the downstream water level under the free flow. The unsteady numerical simulations also are run to simulate the flow in the measuring flume and the instant change of water level. Compared the numerical simulation results with the experiment data, it is concluded that the CFD simulation technique can simulate the flow in the measuring flume so that forecast simulation also can be run to simulate flow in other Airfoil-shaped measuring flumes which have different sizes. It breaks the restraint of physical model test and expands the study extent.6. Application research also are conducted in the irrigation districts that located at the south of Huang-river in the city of Erdos, Inner Mongolia and main channel of diversion project from Daqing river to Qinwangchuan. The result verifies that the Airfoil-shaped measuring flume has a small water head loss, high critical submergence and it is easy to be constructed. The article summarizes the practical experience on the design, construction and calibration, and then gives reasonable advice to the application of Airfoil-shaped measuring flume.The indoor experiments of Airfoil-shaped measuring flume that constructed in three different canals and the field test indicate that the Airfoil-shaped measuring flume can guide the new developmental direction of the measuring flume in the irrigation districts.更多还原