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1.
《灌溉排水学报》2019,(8)
暗管排水工程是控制灌区地下水位,防治耕地盐碱化的主要技术手段。【目的】综合考虑排水条件、排水目的等因素,选择合适的计算方法计算暗管间距。【方法】对几种常用的暗管间距计算方法进行了理论分析并总结了其适用条件,编写了基于VBA的计算程序以实现不同计算方法的优选并确定相应的暗管间距。在此基础上,选取宁夏引黄灌区2个典型暗管排水工程案例进行了分析计算。【结果】稳定流状态下,当kH/q≤100时,宜选择阿维里扬诺夫-瞿兴业公式计算暗管间距,当kH/q>100时,宜选择Hooghoudt公式计算暗管间距;非稳定流状态下,以治渍为目的地区选择按地下水位下降速度计算暗管间距,以防治盐碱化为目的地区选择按排蒸比计算暗管间距。【结论】利用VBA开发的程序可以解决暗管间距计算过程中较繁琐的迭代、累加等计算问题,操作便捷,实用性强;非稳定流方法更适合于宁夏引黄灌区暗管排水间距的计算,银北灌区宜按排蒸比计算暗管间距,银南灌区宜按地下水位下降速度计算暗管间距。 相似文献
2.
A two dimensional saturated-unsaturated Galerkin finite element numerical model was used to predict water table height between
parallel drains. A user-friendly software (DRENAFEM) was developed to allow for the calculation of the distance between drains
and the water table height at middle space between drains. It also allows for determination of variations of the total head
throughout the entire geometric space considered in the model. Such facts lead to the design of flow nets with streams lines
and equipotentials. The numerical drain outflow is also obtained by using the radial flow equation, conservation of mass and
finite element analysis. The results obtained with the model agree well with Khirkam’s and Hooghoudt analytical solution for
the distribution of total head in ideal drains and for the total head calculations midway between drains. 相似文献
3.
The steady state drainage solutions of Ernst, Dagan and van Beers were modified to predict the rate of fall (or rise) of water table midway between drain lines by using the integration technique of Bouwer and van Schilfgaarde. The same assumption to account for the non-uniformity of flux per unit area because of the change in the shape of the water table during recession, was followed.
The integrated equations of Ernst, Dagan and van Beers were compared with the integrated equation of Hooghoudt and of Toksoz and Kirkham which were developed by Bouwer and van Schilfgaarde and the non-steady equation of van Schilfgaarde, using the field data for falling water table collected from subsurface drainage experiment in the saline soil of Mundlana, India. From the comparison of predicted and actual hydraulic heads it was observed that all the equations showed good agreement. No specific trend for the behaviour of different equations could be found from the analysis of field observations at geographically different experimental locations given by Bouwer and van Schilfgaarde, Nwa and Twocock and El-Mowelhi and Hermsmeier. 相似文献
4.
《Agricultural Water Management》1999,42(1):97-109
Heavy textured soils are known for the difficulties imposed to subsurface drainage. Field studies on heavy textured soils in the irrigation commands of India have shown that such soils have relatively more pervious soil at depths greater than 1 m from the ground surface. Considering this fact, a performance study of subsurface drainage in heavy textured layered soils of Mahi Right Bank Canal Command of Gujarat (India) was taken up by modifying the drainage equation of de Zeeuw and Hellinga [de Zeeuw, J.W., Hellinga, F., 1958. Neerslag en Afvoer, Land bocwkundig Tidschrift 70, 405–421] for layered soils, which predicted the water table fluctuations and drain discharge corresponding to irrigation or rainfall inputs taking into account the stratification of the soil profile. The equation was tested on the field data obtained from a pilot project of the study area. The study showed that the watertable head gets influenced by the location of interface between the soil layers. The predicted results conformed with the field data. 相似文献
5.
Mahmoud M. Moustafa 《Irrigation and Drainage Systems》1997,11(4):283-298
The steady-state drainage equation ofHooghoudt (1940) has adrawback that tables for the determination of the so-calledequivalentlayer, de are needed. These calculations arecumbersome as de is dependenton the unknown spacing. Moreover, additional head islost due to theconvergence of stream lines towards the finite numberof perforations withinthe pipe wall. Therefore, corrections are required byreplacing the actualdrain radius by its effective radius. The designers inEgypt assume that thedepth of impermeable layer is infinity which resultsin an over estimationof drain spacing that will affect the ability of thedrainage system.Van der Molen and Wesseling (1991) have developed aseries solution toreplace the Hooghoudts approximation method for theequivalent depth by anexact solution. A comparison between this solution andthose of Lovell andYoungs (1984) and Hooghoudt (1940) showed that theexact solution proved tobe very accurate and efficient solution. The mainobjective of this study isto verify an accurate depth of the impermeable barrierand an effectiveradius of drain pipes which should be used in thedesign process using theexact solution.A field investigation was conducted in a study area of33,138 ha in theNorthern Delta of Egypt within Daqahliya Governorate.The results indicatethat a 5 m depth instead of infinity for theimpermeable layer in Nile Deltaand an effective radius of 90 mm should be used in thedesign process. Theuse of the exact solution for equivalent depth is acrucial issue especiallywith the high rate of on-going drainage projects inEgypt. 相似文献
6.
Simulating basin surface water flow with anisotropic roughness has practical significance. Based on the complete hydrodynamic model, a two-dimensional surface water flow model of basin irrigation with anisotropic roughness was developed in this study by constructing an anisotropic roughness model in the source terms of the governing equation. Then, the simulation performance of the proposed model was analyzed and compared based on typical experiments of basin irrigation. The results show that with basin surface anisotropic roughness, the proposed model can successfully simulate water flow in basin irrigation, and exhibits better simulation performance than the model with isotropic roughness. Three basin geometries and two kinds of inflow geometries were selected for the application of the proposed model. Applied results show that the anisotropic roughness can improve irrigation performance. When the basin width becomes narrow, the physical effect of the rotation angle in the anisotropic roughness model weakens, even becomes smooth. The two-dimensional surface water flow model of basin irrigation with anisotropic roughness provides a good numerical simulation tool for designing and evaluating the performance of basin irrigation system. 相似文献
7.
《Agricultural Water Management》2001,47(2):155-178
The method for verification of numerical solution of water flow towards a drain in homogeneous soil under steady rainfall or steady irrigation recharge is presented in the paper. In 1979, Zaradny and Feddes proved that the accuracy of the numerical result depended, among other things, on the size and pattern of discretization applied. Ibidem, a partly verification of numerical solution was presented. It was based on the Thiem–Dupuit well formula and on the hodograph solutions given by Van Deemter [Van Deemter, J.J., 1950. Versl. Landb. Onderz. 56 (7), 1–67] and Childs [Childs, E.C., 1959. J. Soil Sci. 10 (1), 83–100]. Up till now, there was no full verification of this solution. The proposed method which depends on replacement of the drain by horizontal ‘well’ in a confined aquifer of a constant thickness, the geometry of which in the x–z plane is compatible, in shape and size, with saturated zone in the numerical solution gives the possibility of such verification. For this problem groundwater flow can be described by the Laplace equation. The analytical solutions for the hydraulic head φ and the stream function ψ, specification of boundary conditions for the considered problem and the method of determination of the Fourier series constants are given in the paper. Presented results confirm the correctness of numerical solution given by Zaradny and Feddes [Zaradny, H., Feddes, R., 1979. Agric. Water Manage. 2, 37–53] and they also show that when verification with respect to observed and measured data is impossible, such tests should be performed. 相似文献
8.
为利用锥辊轧制出符合要求的绞龙叶片,采用公式计算的方法,对轧制过程中绞龙叶片的直径和螺距形成原理进行力学分析,并探讨了绞龙叶片与锥辊的干涉条件。研究表明：轧制力矩、变形区的应力应变状态和平衡微分方程比较复杂,可根据已有的理论进行分析;在对锥辊锥角、轧辊转速、轧制时轧材进入轧辊的状态及形式等参数进行组合调整的基础上,选择可行的组合加以分析研究,对绞龙叶片的轧制具有一定的现实意义。 相似文献
9.
《Agricultural Water Management》2006,79(2):113-136
DRAINMOD was run for 15 years to predict and compare drain flow for three drain spacings and crop yield for four drain spacings at the Southeastern Purdue Agricultural Center (SEPAC). Data from two continuous years of daily drain flow from one spacing were used to calibrate the eight most uncertain parameters using a multi-objective calibration function and an automatic calibration method. The model was tested using the remaining field data for the 5, 10, and 20 m drain spacings for drain flow and the additional 40 m spacing for yield predictions. Nash–Sutcliffe efficiency (EF) for daily drain flow simulations for the calibration years and drain spacing ranged from 0.62 to 0.79. The daily EF for model testing ranged from −0.66 to 0.81, with the average deviations of 0.01 to 0.07 cm/day and standard errors of 0.03–0.17 cm/day. On a monthly basis, 91% of plot years had EF values over 0.5 and 76% over 0.6 for years with on-site rainfall data. The total yearly drain flow was predicted within ±25% in 71% of plot years, and within ±50% in 93% of plot years with on-site rainfall data. Statistical tests of daily drain flow EF values for three spacings and percent errors of crop relative yield for four spacings indicated that the reliability of the model is not significantly different among different spacings, supporting the use of DRAINMOD to study the efficiencies of different drain spacings and to guide the drain spacing design for specific soils. In general, the model correctly predicted the pattern of yearly relative yield change. The relative corn (Zea mays L.) and soybean (Glycine max L.) yields were well predicted on average, with percent errors ranging from 1.3 to 9.7% for corn and from −3.3 to 10.3% for soybean. 相似文献
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11.
设有复式空气阀的管道充、放水过程 总被引：2，自引：0，他引：2
为了研究长距离有压管道充水和放水过程中管内气体压力的变化情况,并保证其运行中的安全,针对长距离有压管道的特点,对其充水和放水过程,采取了对整个管道进行分段处理、依次充水和放水的策略.对于分段后的每一段管道,建立了圆形管道内水体体积与水深关系的数学模型.按照小流量充水的原则,运用理想气体状态方程,结合复合式空气阀的进气和排气性质,在空气阀和泄水管布置情况已知的前提下,根据不同的充水流量和放水流量,计算各管段气体压力的变化情况.整个数值计算过程采用自编Fortran程序计算求解.计算结果表明：充水和放水的流量越大,对应管段的气体压力越大和越小,管道越危险;在不影响管道安全性的前提下,为了使管道尽快充满和放空,应采取较大的充水流量（16 m3/s）和放水流量（泄水阀全开）. 相似文献
12.
以四元件Burgers模型作为水田土壤的通用流变模型，通过将随时间随机增长的压力简化为时间的阶梯函数导出了动载条件下水田土壤的压力一下陷量一时间曲线，并提出了据此曲线用最优化理论计算土壤流变参数的方法；在此基础上，研制了一种基于虚拟仪器原理的动载式水田土壤流变仪。该种仪器可自动完成测量数据的采集、贮存及流变参数的计算。试验表明，该仪器所测的土壤流变参数与据静载下土壤的蠕变曲线计算的流变参数数值基本一致。 相似文献
13.
The mechanism of silting up of tile field drains in two heavy textured surface water gley soils was examined by comparing the physical and mineralogical characteristics of deposits in drains with those of the clay soil directly above. The deposits consist of clay, silt and sand and are distinctly laminated. They appear to be the result of internal erosion of the soil. The processes operative seems to have been: (a) inflow of soil through the drain joints; (b) sedimentation in the drain; (c) elution of very fine material. It is possible that this silting-up phenomenon is not uncommon in the tile field drains of surface water gley soils of Scotland. 相似文献
14.
The use of peatlands in the humid tropics requires drainage to remove excess rainfall. The design principles for the drainage systems currently being implemented on peatlands are the same as for mineral soils. The objective of such systems is the timely removal of excess rainfall by surface runoff. For peatlands, with their different soil-hydraulic characteristics, these systems have resulted in poor watertable control and high rates of irreversible subsidence. Concerns about this rate of subsidence and the level of sustainability of the present land use have prompted a study to develop a new water management system. This new system includes a shift from a drainage system that focuses on discharge of excess water towards a system that combines drainage and water conservation. In the new two-step design, the drain spacing and corresponding drain discharges are obtained with a steady-state approach. These outputs are used to calculate the capacity of the drains, including control structures, using an unsteady-state approach. The new system results in a shallower but more narrowly spaced drainage system and maintains a more constant but relatively high watertable and reduces subsidence. It should be remembered however, that even with the improved water management, subsidence cannot be arrested; it is the price one has to pay for the use of tropical peatlands. 相似文献
15.
为方便灌水,一般要求农田具有一定的坡度。在倾斜的地面上进行农田排水计算时,会与水平地面有所差异。本文应用数学方法得到了地面倾斜条件下,考虑蒸发影响时求解Boussinesq方程的精确解析解。计算表明：地面坡度对地下水位变化影响较小,如在坡度分别为1/75-1/200时,排水第四天后,相同点的地下水位与水平地面相比,仅有0.04-0.07m的变化;但由于地面坡度而产生的两侧排水沟水位不同对地下水位有较大的影响,地下水位变化在0.08-1.0m,且越靠近上游,变化越大。因此,在有坡度地面上,应考虑倾斜地面对排水计算的影响。 相似文献
16.
The flow towards drain pipes with and without filters was investigated by means of numerical solutions. Conformal mapping of the actual flow plane onto a plane with parallel flow allowed the development of a method to find the distribution of the potential around the drain pipes. Solutions for two-dimensional flow were obtained. Although in actual cases three-dimensional flow will occur, the solutions obtained may be used to find the relative influence of performation pattern, filter thickness and filter conductivity on the effectiveness of the drain. Examples of the influence of these factors on the entrance resistance and effective diameter of some drains are given. Conditions in which the filter is partly blocked by soil material were also treated. 相似文献
17.
在已有经典导水率模型的基础上,基于分形理论重新探讨了经典模型。从分形几何角度对Millington-Quirk表达式重新进行了解释,以便可以从孔隙率中推导出分形维数,据此推导出了与经典模型相似且更简单的非饱和土壤导水率的分形表达式。基于Brooks-Corey公式获得了k(θ)的幂函数形式,且推导出的幂指数是合理的。 相似文献
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19.
旱田田间排水沟的排水水流一般为非恒定流，一般采用复杂的迭代法计算这类排水沟的间距。为简化计算，作者提出了一种更简便的迭代算法，并导出了可直接计算出排水沟间距的实用公式。 相似文献
20.
The problem of two-dimensional non-steady flow of water towards a drain in saturated—unsaturated soil is solved by a Galerkin-type finite element approach. Special emphasis is placed upon the type of boundary conditions to be used at the circumference of the drain, the hydraulic conductivity of the soil and the discretization scheme of the finite element network. Numerical solutions are compared with the Thiem—Dupuit well formula and with hodograph solutions given by Van Deemter (1950) and Childs (1959). 相似文献