Depth-Averaged Model of Open-Channel Flows over an Arbitrary 3D Surface and Its Applications to Analysis of Water Surface Profile

A new set of depth-averaged equations is introduced to study the flow over an arbitrary three-dimensional (3D) surface. These equations are derived based on a generalized curvilinear coordinate system attached to the 3D bed surface, therefore it allows us to include the effect of centrifugal force due to the bottom curvature. These general equations make it possible to analyze flows over complex terrain without the limitation of mild slope assumption used in conventional depth-averaged models. This new model is then applied to calculate the water surface profiles of (1) flow over a cylindrical surface; (2) flow over a circular surface; and (3) flow with an air-core vortex at a vertical intake. A simple hydraulic experiment is conducted in the laboratory to observe the water surface profile of flow over a circular surface. The results obtained from the model are in good agreement with experimental measurements and calculation by an empirical formula. Consequently, it demonstrates the applicability of the model in cases of flow over a highly curved bottom.     

Measurements of Water Surface Profile and Velocity Field at a Circular Pier

Flow around a 60-mm-diameter pier on a smooth bed was measured in an open-channel flume. By varying the approach flow velocity and water depth, a wide range of subcritical flow conditions was produced. Water surface elevation was measured at 0, 90, and 180° to the approach flow direction near the surface of the pier; and three-dimensional velocity vector field around the pier was measured in two horizontal planes, one close to the bed and the other near the free surface. The velocity field measurements were obtained using a stereoscopic particle image velocimetry system. It was found that the change in water surface elevation around the pier was related to the Froude number and relative water depth. However, no direct relationship between the Froude number and the measured velocity fields was found. The approach flow conditions affected the pier flow field mainly behind the pier; the flow pattern was related to the pier Reynolds number. It was also found that the direction and magnitude of the ensemble-averaged velocity field was more dependent on the pier Reynolds number near the bed.     

Prediction of the Asymptotic Water Depth in Rough Compound Channels

We report on a curious result related to the computation of the asymptotic depth in rough compound channels by one-dimensional approaches. Such approaches, which are widely used in practice, utilize one of a number of well-established methods for estimating the equivalent composite/compound roughness. It was found that many of these methods yield predictions of the asymptotic water depth which erroneously depend on the initial, control, depth. Only one of the methods examined was found not to exhibit this unsatisfactory behavior. We explain the results by analysis of the governing equations.     

摩擦表面再生技术在给水泵上的应用

介绍摩擦表面再生技术在给水泵上的应用情况，对比分析了技术应用前后的设备性能及节能效果。     

板坯连铸结晶器流场及液面波动的水模研究

以我国实际生产的某连铸结晶器为原型,建立1∶1有机玻璃水模型,研究了不同结晶器断面、不同中间包液位下,板坯连铸结晶器流场形态和结晶器液面波动情况,研究发现中间包液位的变化对结晶器液面流场和波动产生影响;同时中间包液位改变了水口出口的压力和流速,进一步影响结晶器流场和液面波动.实验工况条件下,最佳中间包液位的稳定高度为800 mm.建议生产过程稳定控制中间包液位,以提高连铸坯质量.     

Development of Water Quality Indexes to Identify Pollutants in Vietnam’s Surface Water

This study presents the first water quality indexes developed to evaluate surface water in Vietnam. The basic water quality index (WQIB) can be effectively used to evaluate the spatial and temporal variations of surface water quality as well as to identify water pollutants. The overall water quality index (WQIO) can provide additional information, particularly on toxic substances contributing to water pollution. The water quality indexes developed for this paper were applied to the national surface-water quality monitoring data taken from 1999 to 2007. Water pollutants were classified into three subcategories: organic and nutrients, particulates, and bacteria. Surface water in northern and central Vietnam was poor in quality and contained organic matter, nutrients, and bacteria. Water in the southern part was mainly polluted by bacteria. Trend analysis results reveal a deterioration in water quality in those provinces under pressure from rapid population growth, urbanization, and industrialization. Vietnam has established an official policy to ensure comprehensive nationwide water quality monitoring by 2020. The implementation of water quality indexes may provide the guiding data for sustainable water-resources management in Vietnam.     

Importance of Field Data in Stream Water Quality Modeling Using QUAL2E-UNCAS

The Stream Water Quality Model QUAL2E-UNCAS is widely used to simulate the dissolved oxygen of streams under steady flow conditions. It is the latest version of a series of water quality models that have a long history in systems analysis in water quality management, and has been applied to a number of streams and rivers around the world. This paper summarizes the conceptual representation of the computer model, briefly reviews a number of applications of the model that have been published in open literature, describes the included uncertainty analysis capability, and discusses the importance of field data in model predictions. Experience with the QUAL2E model has proven the importance of site-specific data to model predictions. An accurate representation of the properties of the system significantly contributes to simulation success.     

Removal of Antibiotics from Surface and Distilled Water in Conventional Water Treatment Processes

Conventional drinking water treatment processes were evaluated under typical water treatment plant conditions to determine their effectiveness in the removal of seven common antibiotics: carbadox, sulfachlorpyridazine, sulfadimethoxine, sulfamerazine, sulfamethazine, sulfathiazole, and trimethoprim. Experiments were conducted using synthetic solutions prepared by spiking both distilled/deionized water and Missouri River water with the studied compounds. Sorption on Calgon WPH powdered activated carbon, reverse osmosis, and oxidation with chlorine and ozone under typical plant conditions were all shown to be effective in removing the studied antibiotics. Conversely, coagulation/flocculation/sedimentation with alum and iron salts, excess lime/soda ash softening, ultraviolet irradiation at disinfection dosages, and ion exchange were all relatively ineffective methods of antibiotic removal. This study shows that the studied antibiotics could be effectively removed using processes already in use in many water treatment plants. Additional work is needed on by-product formation and the removal of other classes of antibiotics.     

Biphasic Decay Kinetics of Fecal Bacteria in Surface Water Not a Density Effect

The decay of fecal bacteria in surface water often follows a biphasic pattern with the apparent first-order rate constant relatively high during a first phase and lower in a second one. This could be the result of population heterogeneity in resistance due to various mechanisms (different strains, genetically or nongenetically differentiated cells, different growth or cell cycle stage, clumping, hardening), or the specific decay rate could be directly or indirectly affected by the cell density (e.g., quorum sensing). All these mechanisms can theoretically produce a biphasic decay pattern and are consistent with the literature. However, they are fundamentally different and lead to different behavior of mechanistic total maximum daily load models, so identifying the correct mechanism is important. This technical note presents the results of a study aimed at determining if a density effect is involved. Laboratory decay experiments with pure strain Escherichia coli cells in phosphate buffer were conducted over a range of initial densities. The results show that the rate constant changes after a certain time, rather than at a certain density, which is inconsistent with a density effect. As the experiments were performed with a pure strain, the resistant fraction cannot be attributed to a different strain. Further research is needed to identify the mechanism responsible for the population heterogeneity.     

高压水除鳞喷嘴与射流特性的试验研究

在热轧板带生产尤其是薄板坯连铸连轧工艺中 ,除鳞是提高产品表面质量的关键工序之一 ,目前国内外普遍采用高压水除鳞技术。其中除鳞喷嘴的结构直接影响到射流的打击力及其分布形式 ,对除鳞效果起决定性作用。对高压水除鳞喷嘴的结构及其和水射流的特性之间的关系进行了大量的试验研究 ,总结出了射流散射角、喷射宽度方向特性、轴心打击力的变化规律 ,并对喷嘴结构参数的选择提出了见解。     

Experimental Study on the Multisegment Regime of the Water Flow in Drip Emitters

The flow exponent greatly determines the hydraulic performance of drip emitters. The objective of this study is to reveal the change of flow exponents with different water pressures. Laboratorial experiments of the relationship between discharges and water pressures were conducted with five types of drip emitters used for surface drip irrigation systems. The regression for calculating flow exponents was done with different segment pressures. The results showed that the flow exponent reduced gradually with the increase of the pressure segment except a brief increase in the early stage of pressure increasing due to the channel expansion. The eddy drip-arrow is most suitable for the pressure ranges of 2–8 and 8–14?mH2O. The effect of the use of the small diameter drip-tube is best in the high-pressure range of 17–25?mH2O. The relation between average flow velocities and water pressures is characterized by the flow exponent, the same as that between emitter discharges and water pressures. The eddy drip-arrow and the in-line drip-tape with a low discharge but a high flow velocity can meet the requirements of both prominent anticlogging and long-distance use. The Reynolds numbers of the five types of drip emitters range from 200 to 1,800, below the critical value of the turbulent transition of a conventional scale flow. The small diameter drip-tube needs the lowest Reynolds number required for full turbulence transition which assures a lower flow exponent when the emitter runs with a relatively low discharge.     

简述水面冷却池在某工程中的应用

介绍了水面冷却池的特点,简要分析了水面面积有限、右面面积较大的两种水面冷却池类型的运行原理、应用效果以及注意事项,并以某铜冶炼项目渣包喷淋冷却水冷却工艺为例,对冷却方案的选择、设备配置、设计计算进行了论述。     

Applicability of Quasisteady and Axisymmetric Turbulence Models in Water Hammer

Two of the existing turbulence water hammer models, namely the two-layer and the five-layer eddy viscosity models, are implemented and analyzed and the accuracy of their quasi-steady and axisymmetric assumptions evaluated. In addition, a dimensionless parameter P (ratio of the time scale of radial diffusion of shear to the time scale of wave propagation) for assessing the accuracy of quasi-steady turbulence modeling in water hammer problems is developed and applied. It is found that the results of both models are in reasonable agreement, confirming that the turbulence modeling of water hammer flows is insensitive to the magnitude and distribution of the eddy viscosity within the pipe core. Comparison of model results with available data shows that the quasi-steady assumption becomes more accurate as the dimensionless parameter P increases. Furthermore, the analysis shows that the quasi-steady assumption is highly accurate as long as the simulation time is below the diffusion time scale and that this assumption causes an almost linear increase in the difference between model results and data with time. The accuracy of the flow axisymmetry assumption is evaluated by applying both models to a water hammer problem where flow asymmetry has been observed experimentally. It is found that the difference between models and data grows exponentially and reaches 100% after six wave periods.     

Evaluation of Bacillus Spore Survival and Surface Morphology Following Chlorine and Ultraviolet Disinfection in Water

The objective of this paper is to evaluate the change in Bacillus subtilis spore survival and dimensions following ultraviolet and chlorine disinfection in water. Disinfection was monitored by using tools such as atomic force microscopy (AFM), particle sizing by the electrozone sensing technique and fluorescence of spores after staining with an optical brightener. Results indicated that there was a change in the adsorbed fluorescence following chlorine; however, the magnitude of this change was only approximately twofold at 90% of spore kill. In addition, changes in spore particle-size distribution following chlorine occur at above 99.9% of spore kill. Even the roughness (RMS), width, and length of spores as measured by AFM change only after about 99% of spore killing with chlorine. Use of optical brighteners, AFM, and sizing are not sensitive enough for detecting the disinfection of chlorine-resistant spores and as expected no changes occurred with ultraviolet treated spores. Even though, these techniques may have the potential for determining oxidative disinfection and for the development of monitors and sensors of chemical disinfection for chlorine-sensitive microorganisms.     

Identifying Two-Dimensional Characteristics of Surface Water Hydraulics in an Irrigated Paddy Field

To efficiently manage the water supply for paddy rice and to reduce the inundation damage from floods, it is necessary to enhance our understanding of the characteristics of the surface water hydraulics in an irrigated paddy field. In this study, a two-dimensional numerical model is used, and the model’s applicability for simulating surface irrigation and drainage is evaluated. The model’s Manning roughness coefficient is estimated, taking into account the growth stage of the paddy rice; the simulation results are in good agreement with the observations. Model simulations reveal that the initial ponding depth affects the wave propagation and the increase in water depth during irrigation. There are few differences in piezometric heads among the positions except for those close to the outlets during drainage. Constructing drainage ditches in a paddy field reduces the drainage time to 24 h. Also, the study results reveal that it is preferable to determine the appropriate water management measures by considering the characteristics of the surface water hydraulics of paddy fields to reduce costs and labor input.     

Model for the Simulation of Water Flows in Irrigation Districts. I: Description

Significant improvements in the profitability and sustainability of irrigated areas can be obtained by the application of new technologies. In this work, a model for the simulation of water flows in irrigation districts is presented. The model is based on the combination of a number of modules specialized on surface irrigation, open channel distribution networks, crop growth modeling, irrigation decision making, and hydrosaline balances. These modules are executed in parallel, and are connected by a series of variables. The surface irrigation module is based on a numerical hydrodynamic routine solving the Saint Venant equations, including the heterogeneity of soil physical properties. The simulation of water conveyance is performed on the basis of the capacity of the elements of the conveyance network. Crop growth is simulated using a scheme derived from the well-known model CropWat. The irrigation decision making module satisfies water orders considering water stress, yield sensitivity to stress, multiple water sources, and the network capacity. Finally, the hydrosaline module is based on a steady state approach, and provides estimations of the volume and salinity of the irrigation return flows for the whole irrigation season. The application of the model to district irrigation management and modernization studies may be limited by the volume of data required. In a companion paper, the model is calibrated, validated, and applied to a real irrigation district.     

高水速凝材料在宁东矿区充填开采中的应用

宁东矿区是国家规划的13个亿吨级大型煤炭基地之一,同时也是国内少有的百亿吨级整装煤田。煤炭是我国的主要能源之一,但是在资源开采中为了提高经济效益,易形成采空区,产生地表沉陷等问题。为了减少地表沉陷,会使用煤柱在采空区进行支撑,但会造成大量煤炭的损失,不符合国家的可持续发展战略。在考虑了相关地质条件后,为了避免地表沉陷和造成煤炭损失,采用充填开采的方式开采煤炭资源,并用高水材料来代替煤柱,提高充填堆积体的整体强度和空间刚度,增强充填体对巷道顶部的支撑能力,降低了煤矿在掘采过程中巷间煤柱失稳的概率;同时,采用高水材料代替煤柱进行填充,提高煤炭资源的利用效率。     

Theoretical and Experimental Study on Water Offset Flow in Fluidic Component of Fluidic Sprinklers

Compared with other rotating sprinklers, the fluidic sprinkler controlled by an outlet clearance has a simpler structure and better hydraulic performance. The offset effect, happening in the fluidic component of the sprinkler, drives the sprinkler and controls its rotational direction. Theoretical and experimental research are conducted to study the water offset jets with a small ratio of 0.675 for the 10PXH sprinkler and 0.355 for the 30PXH sprinkler in the fluidic components. Analytic solutions and other calculations deduce the reattachment lengths of the offset jets. Computational fluid dynamics (CFD) software simulates the offset flows in simplified models and real models of the fluidic components, in two dimensions and three dimensions, respectively, utilizing the volume of fluid (VOF) method to trace the shape of the interface between water and gas. Simulation results of the sidewall pressure distribution also obtain the reattachment lengths. The resulting experimental measurements of the static pressure and reattachment length are in line with the predicted results of the calculations and the simulations. These results indicate that CFD simulation can approximate the offset flow in fluidic components. On the basis of this study, some of the component sizes are confirmed.