迷工滴头内流动的有限元数值分析

借助笛卡尔坐标系下时均Ｎａｖｉｅｒ－ＳＥｔｏｋｅｓ方程，采用加罚有限元数值方法模拟了“圆弧型迷宫”式滴头内流动场，在数值计算的基础上，对滴头内流动场进行了分析。并针对防堵塞要求，对该滴头进一步优化设计提出了合理建议。     

滴头流道内部水流流动机理研究韵进展与问题

总结了滴头流道内水流流动机理研究的进展情况,分析了研究滴头流道内水流流动机理的3种方法（理论分析方法实验研究方法及数值模拟方法）的具体内容和存在的问题。针对这些问题,对滴头流道内流动机理的研究方向提出了建议。     

滴头流道内部水流流动机理研究的进展与问题

总结了滴头流道内水流流动机理研究的进展情况,分析了研究滴头流道内水流流动机理的3种方法(理论分析方法实验研究方法及数值模拟方法)的具体内容和存在的问题。针对这些问题,对滴头流道内流动机理的研究方向提出了建议。     

基于流固耦合方法的压力补偿滴头水力特性研究

采用流固耦合方法对压力补偿滴头水力特性进行了数值模拟,得到了该滴头的压力流量关系、内流场分布及膜片变形量。通过与试验实测结果的对比分析表明,数值模拟与实测的滴头压力流量关系较接近,为研究压力补偿滴头内流场分布与水力特性之间的关系提供了一种新途径。     

迷宫滴头CFD模拟精度影响因素的正交试验分析

近几年出现的计算流体动力学(CFD)数值模拟方法已经成为滴头研究中的重要手段.在利用FLUENT求解器对迷宫滴头流道内流场进行CFD数值模拟时发现:当对求解器进行不同设置时,CFD模拟精度存在较大差别,因此有必要对影响滴头CFD模拟精度的主要因素进行分析,找出合理设置求解器的方法,以便CFD数值模拟可以取得理想的模拟精度.利用FLUENT软件对迷宫滴头流道内流场进行了数值模拟,并与实测结果进行对比,对影响滴头CFD数值模拟精度的主要因素进行了正交试验分析,研究了网格单元尺寸、CFD计算模型和近壁面处理方式对CFD模拟精度的影响特性.找出了能使CFD数值模拟取得理想精度的求解器设置方法.     

压力补偿滴头流动阻力分析与流量预测研究

为探究压力补偿滴头流动阻力产生的主要部位、变化及对滴头流量的影响,采用基于雷诺平均维纳-斯托克斯(RANS)模型的瞬态和稳态流固耦合计算方法,模拟研究了压力补偿滴头流体与弹性片之间的相互作用,分析了工作压力0~300kPa范围内弹性片变形、流动阻力与流量之间的关系。结果表明：数值模拟能够准确预测一定工作压力范围内压力补偿滴头的流量,不同工作压力下滴头流量模拟值与实测值的平均误差为12.32%。弹性片的变形经历快速变形、缓慢变形和长期微小变形3个阶段。随着弹性片变形程度增加,迷宫流道压力损失占比逐渐减小,压力补偿腔和副流道压力损失明显增加。流动阻力主要发生在迷宫流道、弹性片与凸台之间,弹性片接触凸台前,流动阻力主要取决于迷宫流道的能耗,滴头流量随工作压力的增加而增长。弹性片接触凸台后,流动阻力为工作压力的线性函数,滴头流量在一定压力范围内保持恒定;主流道结构影响压力补偿滴头的最小补偿压力,副流道结构对压力补偿滴头的流量调节作用具有重要影响。     

矩形迷宫式滴灌灌水器的模拟研究

利用Fluent软件对滴灌灌水器流道内流体流动进行了数值模拟,得到了流道压力图、流速矢量图。根据流道内流线变化对灌水器流道结构进行了优化设计,采用了圆弧形流道结构。通过优化前、后的速度矢量图可知:优化后的滴头流道涡旋区和低速滞止区基本消除,虽然在流道拐弯处的小部分区域内流体流动速度仍有些偏高,但是从流道整体来看,优化后的流道内主流速度分布比较均匀,且流体充满整个流道,大大提高了灌水器的抗堵塞性能。     

HD型石油化工流程泵双蜗壳内部流场数值计算

180°对称分布的双蜗壳结构在大型离心泵中应用广泛,但目前对双蜗壳内部流动规律的数值研究还相对较少。为了探究双蜗壳流道内部流动规律,利用CFD软件,基于雷诺时均N-S方程和k-ε紊流模型,通过SIMPLE算法进行压力速度耦合,对双吸式HD型石油化工流程泵蜗壳流道内部流场进行了数值模拟,得到了蜗壳内的速度场以及压力场的分布规律,并重点分析了隔舌和扩散段内的流动。数值结果表明,蜗壳内的速度场以及压力场分布相对比较均匀,在隔舌和扩散段内存在一定的回流和涡流,但并不影响泵的良好性能和高效率。     

水肥一体化对侧翼迷宫滴灌带抗堵塞性能的影响

为从普遍应用的侧翼迷宫滴灌带中优选出随水施肥中抗堵塞性能最佳的流道结构,为探明随水施肥过程中侧翼迷宫滴灌带滴头堵塞影响因素以及堵塞机理,根据大田滴灌系统清水与肥水交替运行的方式,通过长周期间歇性施加磷肥进行灌溉施肥试验,对3种流道结构的侧翼迷宫滴灌带抗堵塞性能进行了测试,并且利用CFD方法数值模拟滴头流道内流场分布,与试验结果提供参考和对比,试验结果显示:新型欧姆链式流道的抗堵塞性能明显优于普通几字形流道,其流道内最大速度明显高于另外两种滴头;对堵塞位置的观测发现几字形滴灌带后段易发生堵塞,其中1号滴灌带堵塞从后段逐渐向上游延伸,而2号滴灌带堵塞滴头则是由前段和后端向中游延伸。     

动态水压对迷宫流道滴头抗堵塞性能影响与机理分析

为缓解浑水灌溉中滴头堵塞的问题,评估了3种水压模式(恒定水压、台阶波形水压、三角函数波形水压)对滴头堵塞的控制效果,并对不同水压模式下滴头内堵塞物质、滴头排出物质的级配和粒径进行分析。结果表明：动态水压处理滴头使用寿命延长了79.06%,滴头抗堵塞性能优于恒定水压处理;波形对滴头抗堵塞性能影响较小,两种不同波形动态水压处理滴头的使用寿命仅相差2.77%。动态水压处理流道内水流紊动剧烈,能更好地移除沉积、附着在迷宫流道内的堵塞物质,与恒压处理相比,滴头内黏粒、粉粒堵塞物质分别减少了22.19%～36.75%和13.22%～25.06%。动态水压处理下滴头排出泥沙的粒径增大,最大粒径比恒定水压处理增大了44.34%,动态水压处理迷宫流道内水流流线时刻发生变化,水流的挟沙能力增强,大颗粒泥沙更容易从滴头排出。     

The effect of drip line spacing, irrigation regimes and planting geometries of tomato on yield, irrigation water use efficiency and net return

This study was conducted in order to determine the effect of drip line spacing, irrigation regimes and planting geometries of tomato on yield, irrigation water use efficiency (IWUE) and net return. The experiments were carried out in the conditions of Eskisehir in Central Anatolian part of Turkey, between 2003 and 2005, with cv. Dual Large F1 tomatoes (Lycopercion esculentum L). The maximum yield of 121.1 t ha⁻¹ was obtained from the treatment in which both the lateral and row spacing were 1 m, and irrigated with water amount based on the percentage of canopy cover. The seasonal irrigation water amount of the treatment was 551 mm. Tomatoes yield of 109.9 t ha⁻¹ was obtained under conditions of 491 mm seasonal irrigation water applied for the 2-m lateral spacing in which two plant rows (twin rows) were planted 0.35 m on either side of the lateral with a row spacing of 0.70 m across the drip lateral and 1.30 m in the interrow between each set of twin rows. Although water saving of 60 mm and investments economy of 40% were provided from the twin-row design, the yearly return of the design including one lateral for each row was US$ 1590 ha⁻¹ higher than that the return of the twin-row design. The method of determination of irrigation water amount based on the percentage of canopy cover appeared to be the most reasonable and effective one in terms of the yield and IWUE. On the other hand, the maximum irrigation water use efficiency (22.3 kg m³) was obtained from 2-m lateral spacing and the percentage of canopy cover for calculation of the amount of irrigation water applied. Thus, canopy cover may be used successfully at any lateral design conditions.     

多孔管允许最大长度的计算

导出了不同地面坡度的多孔管允许最大长度公式，这一成果可用于喷灌及微灌工程的规划设计。     

The effect of drip line placement on yield and quality of drip-irrigated processing tomatoes

Subsurface drip irrigation of processing tomatoes is increasing in California. The common design approach is to bury drip lines 0.2–0.36 m deep in the middle of the plant row, which places drip lines directly beneath plant rows. This design limits the use of the drip irrigation system to only those crops compatible with this drip line and bed spacing, and thus, other design approaches are being investigated to increase the flexibility of the drip systems. These approaches are installing drip lines in alternate furrows and installing drip lines in every furrow, both of which place drip lines midway between plant rows. The furrows are the result of the cultural practices used to form beds for planting.This study investigated the effect of the different drip line placements on crop yield and quality. Results showed that the highest yields occurred for the buried placement and the smallest yields for the alternate furrow placement. For the buried placement, soil water content and root density were concentrated around the drip lines, directly beneath the plant rows, while for the furrow placements, zones of high soil water content and root density did not coincide with the plant rows. However, some growers have found the furrow placement to reduce some of the disease problems normally experienced with the traditional furrow irrigation methods.     

Effect of filter, emitter and location on clogging when using effluents

The effect on emitter clogging of four filtration systems (sand, screen, disc and a combination of screen and disc filters) and six emitter types placed in laterals 87 m long, using two different effluents with low suspended solid levels from a wastewater treatment plant, was studied for 1000 h. Four of the emitters were molded and welded into dripline wall, two of them being pressure-compensated and the other two non-pressure-compensated. The other two emitters, both pressure-compensated, were inserted into thick wall. Emitter clogging was affected mainly by emitter type, location along the lateral and the interaction between these two factors. Differences among emitters with larger clogging were only observed at the end of dripline. Two molded and welded emitters showed the worst performance: one non-pressure-compensated with the lowest passage section, and the other pressure-compensated that, after 800 h working at higher dripline flow and particle load, experienced an important decrease in flow rate. Only with the effluent that had a higher number of particles, did the filter and the interaction of filter and emitter location have a significant effect. Emitters placed after screen and sand filters showed the largest flow rates at the lateral ending, even though only sand filtration significantly reduced turbidity and suspended solids. Emitters protected by a disc filter experienced the largest flow rate reductions.     

Water balance of apricot trees (Prunus armeniaca L. cv. Búlida) under drip irrigation

The water balance of drip irrigated apricot trees (Prunus armeniaca L. cv. Búlida grafted onto “Realfino” apricot rootstock) was determined during a 30-month-period. Two irrigation regimes based on the reduction coefficients of Class A pan evaporation (1 and 0.5) were used to determine the water consumed. The water balance parameters for these treatments are shown and discussed in detail. Overall, the trees receiving less water showed 35% less evapotranspiration. Crop coefficients calculated on the basis of the water balance over a 30-month-period led to a saving of almost 14% water, since the coefficients were slightly below those used in other apricot orchards in the same area.     

Short-term watering-distance and symmetry effects on root and shoot growth of bell pepper plantlets

Drip lines were located at distances ranging from 0 to 60 cm from one or both sides of a row of pepper plantlets, and we monitored the effects on their shoot development during 76 days from transplanting to full-size first fruits, on the final root system, and on the areal water and salt distributions in the upper 15-cm soil layer. The experiment was conducted in a greenhouse with a sandy soil, and excess fresh water (1.9 L d⁻¹ per plant) was applied via short daily irrigations. In addition, the effects of watering distance and symmetry on the potential water uptake rate were analyzed with a coupled-source-sink steady flow and uptake model. Initial faster shoot growth with the one-side system and short distances progressively changed to faster growth with the two-side system and longer watering distances, with the optimum at 30-40 cm. These temporal changes are attributed to temporal changes in the root uptake of irrigation water: small plants with small root systems benefit from the larger water supply to a smaller soil volume provided by the one-side system, whereas larger plants with greater water needs could extract more irrigation water when they developed larger, split root systems in the two-side irrigation. Balanced root systems and maximal shoot growth can be obtained by starting the irrigation with a line on each side, near the plants, and moving the lines after a short time.     

精密滴灌灌水器注塑工艺模拟与优化

通过正交优化试验设计,以注塑工艺模拟代替实物进行试验,研究了注塑工艺参数对LDPE材料灌水器制品收缩率的影响。模拟确定了各工艺参数对制品收缩率及收缩率变化的影响度,并优化取得了最佳的注塑工艺参数。在模拟结果的基础上一次试模成功,灌水器制品的流道部分精度达到±0.01mm。     

果树滴灌需水量与灌溉制度试验研究

局部灌溉条件下的需水量与灌溉制度不同于全面积灌溉的情况,本文对此进行了分析论述,并通过对果树滴灌试验资料的分析得出了滴灌条件下的果树需水规律及有关灌溉参数。     

布瑞斯勒（Bresler）从土壤水力参数确定滴头间距的数学模型

滴灌工程设计中,滴头间距对于整个系统的效率、灌水质量来说是一个很重要的参数,而在现有的资料和生产实践中,该值大多是根据实际情况进行估计的。该文介绍布瑞斯勒教授(Bresler)确定滴头间距数学模型的理论基础,以期为滴头间距的确定提供参考。     

Soil–water and solute movement under precision irrigation: knowledge gaps for managing sustainable root zones

Precision irrigation involves the accurate and precise application of water to meet the specific requirements of individual plants or management units and minimize adverse environmental impact. Under precision irrigation applications, water and associated solute movement will vary spatially within the root zone and excess water application will not necessarily result in deep drainage and leaching of salt below the root zone. This paper estimates that 10% of the irrigated land area (producing as much as 40% of the total annual revenue from irrigated land) could be adversely affected by root zone salinity resulting from the adoption of precision irrigation within Australia. The cost of increases in root zone salinisation due to inappropriate irrigation management in the Murray and Murrumbidgee irrigation areas was estimated at AUD 245 million (in 2000/01) or 13.5% of the revenue from these cropping systems. A review of soil–water and solute movement under precision irrigation systems highlights the gaps in current knowledge including the mismatch between the data required by complex, process-based soil–water or solute simulation models and the data that is easily available from soil survey and routine soil analyses. Other major knowledge gaps identified include: (a) effect of root distribution, surface evaporation and plant transpiration on soil wetted patterns, (b) accuracy and adequacy of using simple mean values of root zone soil salinity levels to estimate the effect of salt on the plant, (c) fate of solutes during a single irrigation and during multiple irrigation cycles, and (d) effect of soil heterogeneity on the distribution of water and solutes in relation to placement of water. Opportunities for research investment are identified across a broad range of areas including: (a) requirements for soil characterisation, (b) irrigation management effects, (c) agronomic responses to variable water and salt distributions in the root zone, (d) potential to scale or evaluate impacts at various scales, (e) requirements for simplified soil–water and solute modelling tools, and (f) the need to build skills and capacity in soil–water and solute modelling.