Irrigation Scheduling with Travel Times

In preparing water allocation schedules for fields in a lateral unit, the time required for water to travel from one point on a lateral to another can be significant and is dependent on the sequence in which users abstract water. This paper illustrates the problem of ignoring travel time and/or considering travel time to be sequence independent. For two users, each requesting water for a duration of 4 h, by assuming travel time to be sequence independent, one user receives water for 5 h, a 25% increase, and the other receives water for only 3 h, a 25% decrease. This paper presents a formulation of the irrigation scheduling problem for sequential users with sequent dependent travel time. The formulation is implemented as an integer program and applied to part of a lateral unit on the Juan Distributary, Haryana, India. Two models are presented, the first of which allows for noncontiguous jobs, i.e., idle time is permitted between jobs. The second model does not permit noncontiguous jobs.     

Analysis of Critical Hydraulic Gradient for Particle Movement in Filtration

The objective of this paper is to propose an explicit solution for the critical hydraulic gradient required to move a base particle within a pore channel. The particle is assumed to displace when the applied hydrodynamic forces exceed this critical hydraulic gradient. The current analysis is an extension of a previous study (Indraratna and Vafai 1997), where the limit equilibrium analysis was modified to include the effect of drag in the hydrodynamic force component. The theoretical model was examined in the laboratory using fine gravel filters and a cohesionless base soil consisting of very fine river sand.     

Methodology for Determining Laboratory and In Situ Hydraulic Conductivity of Asphalt Permeable Friction Course

The permeable friction course (PFC) is a layer of porous asphalt pavement overlain on conventional impervious hot-mix asphalt or portland cement concrete. The drainage properties of PFC are typically considered to be governed primarily by two hydraulic properties: hydraulic conductivity and porosity. Both of these hydraulic properties change over the life cycle of the PFC layer due to clogging of the pore space by sediment. Therefore, determination of the hydraulic conductivity and porosity of PFC can be problematic. Laboratory and particularly field tests are necessary for accurately determining the hydraulic conductivity of the PFC layer. Taking multiple measurements over the life of the pavement shows how these hydraulic characteristics change with time and the varying roadway conditions at which they are evaluated. Constant head laboratory testing has shown that PFC experiences a nonlinear flow relationship as described by the Forchheimer equation. In addition to the laboratory analysis of the hydraulic characteristics, a falling head field test is recommended to determine the in situ hydraulic conductivity. This incorporates the modeling techniques used in the laboratory testing and applies them to the falling head conditions used in the field. The result is a nondestructive test procedure for determining the in situ hydraulic conductivity which is necessary for estimating the extent to which the benefits associated with the drainage characteristics of the PFC layer will persist.     

Multiple-Model Optimization of Proportional Integral Controllers on Canals

Canals or open channels that convey water often consist of pools in series separated by control structures. Successful implementation of water-level control with these structures using decentralized proportional integral (PI) controllers depends heavily on the tuning of the control parameters. These parameters are hard to determine due to the interactions between the pools and the varying flow conditions in the canal. This paper presents a procedure for tuning any linear controller (including decentralized PI controllers) that guarantees stability of the controlled canal. It minimizes a cost function that weights the water-level deviations from the target level against control efforts at both low- and high-flow conditions. The procedure is tested on a model of the Umatilla Stanfield Branch Furnish Canal in Oregon. The tests show the capability of the procedure to deal with the pool interactions. The results of a realistic turnout schedule applied to the controlled canal show the high performance of the controllers (small water-level deviations in all pools) over varying flow conditions.     

粗轧机上辊系平衡液压系统的优化改造

粗轧机上辊系平衡液压系统在轧钢过程中出现冲击振动大、管路漏油、元件损坏及系统不稳定现象,造成钢板厚度波动或板型缺陷。经过分析,对上辊系平衡液压系统进行了优化改造,大大减少了冲击振动,提高了生产效率。     

Surface and Subsurface Flow through Block Ramps

Block ramps are permeable hydraulic structures. Flow that enters the block ramp infiltrates between the blocks and eventually on the porous base material on which the ramp is posed. The percentage rate of subsurface flow with respect to the total flow at the entrance of a block ramp or a rock chute is studied experimentally and analyzed by means of dimensional analysis. This quantity is described as a function of related parameters, such as the total inflow discharge, the particles’ characteristics, the thickness of the base material bed, the geometric characteristics of the block ramp, and the boundary conditions at the toe of the ramp itself. The experimental data were elaborated in order to supply new formulations of the flow discharge through the base ramp material and the block ramp energy dissipation. The amount of energy losses of such structures is essentially a function of the geometry and the bed surface characteristics of the ramp, the hydraulic conditions, and the percentage rate of the subsurface flow.     

Integrated Genetic Algorithm for Optimization of Space Structures

Gradient‐based mathematical‐optimization algorithms usually seek a solution in the neighborhood of the starting point. If more than one local optimum exists, the solution will depend on the choice of the starting point, and the global optimum cannot be found. This paper presents the optimization of space structures by integrating a genetic algorithm with the penalty‐function method. Genetic algorithms are inspired by the basic mechanism of natural evolution, and are efficient for global‐searches. The technique employs the Darwinian survival‐of‐the‐fittest theory to yield the best or better characters among the old population, and performs a random information exchange to create superior offspring. Different types of crossover operations are used in this paper, and their relative merit is investigated. The integrated genetic algorithm has been implemented in C language and is applied to optimization of three space truss structures. In each case, an optimum solution was obtained after a limited number of iterations.     

Concurrent Genetic Algorithms for Optimization of Large Structures

In a recent article, the writers presented an augmented Lagrangian genetic algorithm for optimization of structures. The optimization of large structures such as high‐rise building structures and space stations with several hundred members by the hybrid genetic algorithm requires the creation of thousands of strings in the population and the corresponding large number of structural analyses. In this paper, the writers extend their previous work by presenting two concurrent augmented Lagrangian genetic algorithms for optimization of large structures utilizing the multiprocessing capabilities of high‐performance computers such as the Cray Y‐MP 8/864 supercomputer. Efficiency of the algorithms has been investigated by applying them to four space structures including two high‐rise building structures. It is observed that the performance of both algorithms improves with the size of the structure, making them particularly suitable for optimization of large structures. A maximum parallel processing speed of 7.7 is achieved for a 35‐story tower (with 1,262 elements and 936 degrees of freedom), using eight processors.     

Hydraulic Analysis of Orlando Easterly Wetland

Hydraulic testing of the Orlando Easterly Wetland, a constructed treatment wetland located near Christmas, Fla., was performed as part of a more comprehensive study of treatment efficacy of the system. The wetland serves to reduce nutrient loading from tertiary treated wastewater to the St. Johns River, the receiving body. Residence time distribution analysis of bromide tracer tests revealed and quantified inefficiencies (short circuiting and dead zones) in the hydraulic performance within individual treatment cells and the wetland system under the operating conditions studied. Hydraulic efficiencies (ratios of experimentally determined residence times to nominal residence times) of the cells ranged from 11 to 88%, while overall, the wetland was operating at near 50% efficiency during the tracer tests. Short circuiting and dead zones within the wetland are largely the results of historic land alterations, such as ditches, that were not removed during the conversion of the site from drained land to managed wetland. Volume- and area-based system-referenced metrics were developed to identify and prioritize opportunities to improve hydraulics on both cell-by-cell and system scales.     

轧机液压AGC伺服缸优化分析

该文以轧机液压AGC伺服缸为研究对象,通过对功率匹配设计方法的分析、比较、优化系统,将优化结果进行仿真并与原有系统的仿真结果进行比较,发现优化后系统的性能优于原系统的性能.     

Concurrent Optimization of Large Structures. I: Algorithms

Parallel algorithms are presented for optimization of structures on shared‐memory multiprocessor computers. Structures subjected to multiple loading cases with limitations on nodal displacements, element stresses, and member sizes are optimized using the optimality‐criteria approach in a concurrent‐processing environment. Emphasis is directed toward parallelizing each computational step of the solution process. Parallel algorithms are developed to assure the best concurrent performance and speed‐up within each step. A substructuring algorithm is used to achieve the best work‐load balance during the solution of the generalized displacements. Concurrency is achieved through the use of the notion of cheap concurrency and the concept of threads. (A companion paper demonstrates the efficiency of the parallel algorithms through optimization of several truss and frame problems on an Encore Multimax shared‐memory computer for a variable number of processors.) The algorithms are particularly suitable for optimization of large structures such as space stations.     

Concurrent Optimization of Large Structures. II: Applications

In a companion paper, we presented algorithms and procedures for concurrent optimization of framed structures on shared‐memory multiprocessor computers. Implementation of the algorithms and applications are presented in this paper. The efficiency and versatility of the algorithms are assessed by presenting four examples. Speed‐ups and work‐load‐balance issues at various steps of the optimization process are considered and discussed. The efficiency of the parallel‐processing algorithms increases with the size of the structure, thus making them particularly suitable for optimization of large structures such as space stations.     

Three-Dimensional Numerical Model for Flow and Bed Deformation around River Hydraulic Structures

This paper describes a numerical model developed to simulate flow and bed deformation around river hydraulic structures. The model solved the fully three-dimensional, Reynolds-averaged Navier–Stokes equation expressed in a moving boundary-fitted coordinate system to calculate the flow field with water and bed surfaces varying in time. A nonlinear k-ε turbulence model was employed in order to predict flow near the structure where three-dimensional flow is dominant. The temporal change in bed topography was calculated by coupling a stochastic model for sediment pickup and deposition using a momentum equation of sediment particles in order to account for the effect of nonequilibrium sediment transport. In validating the numerical model, a spur dike and a bridge pier, which are considered to be typical river-engineering structures, were selected. By comparing the numerical results with observed laboratory experimental data, the model was found to reproduce flow and scour geometry around these structures with sufficient accuracy.     

Case?Study: Application of GPR to Detection of Hidden Dangers to Underwater Hydraulic Structures

After long-term operation, a variety of hidden defects will occur in hydraulic structures, which will endanger the safety of a water conservancy project. In particular, hidden defects located below the water surface cannot be easily recognized by conventional methods and thus constitute the main reason for occurrence of dangerous situations in such hydraulic structures. It is therefore necessary to carry out periodic checks on the underwater structures. Ground-penetrating radar (GPR) is a high-resolution, nondestructive technology for detection of underground objects using a high-frequency electromagnetic pulse, and has been extensively applied to a variety of fields such as engineering/geologic exploration, underground archaeological survey, detection of scour holes around bridge piers, etc. In order to investigate the capability of GPR in detecting hidden dangers to underwater hydraulic structures, the authors have conducted GPR application-related experiments for more than 20 hydraulic projects since 1996, and in order for the GPR application to be successful in narrow spaces such as lock chambers, the authors also designed an antenna that can be directly operated on the water’s surface. Experimental results demonstrate that GPR can be used not only to detect hidden dangers with high precision, such as uneven settlement and cracking at impervious blanket or apron water bottoms, but also to detect hidden dangers to underwater hydraulic structures, such as damage of reverse filter below the sloping clay core of a dam, settlement and cracking of the antiseepage geomembrane at the bottom of a reservoir, concentrated seepage channel, etc. The application effect will be demonstrated in this paper based on some practical examples of using the GPR technique for such types of detection.     

Analysis of Seepage from Polygon Channels

An exact analytical solution for the quantity of seepage from a trapezoidal channel underlain by a drainage layer at a shallow depth has been obtained using an inverse hodograph and a Schwarz-Christoffel transformation. The symmetry about the vertical axis has been utilized in obtaining the solution for half of the seepage domain only. The solution also includes relations for variation in seepage velocity along the channel perimeter and a set of parametric equations for the location of phreatic line. From this generalized case, particular solutions have also been deduced for rectangular and triangular channels with a drainage layer at finite depth and trapezoidal, rectangular, and triangular channels with a drainage layer and water table at infinite depth. Moreover, the analysis includes solutions for a slit, which is also a special case of polygon channels, for both cases of the drainage layer. These solutions are useful in quantifying seepage loss and/or artificial recharge of groundwater through polygon channels.     

Determination of Critical Head in Soil Piping

One of the main mechanisms of failure of levees is a phenomenon called “piping,” which generally begins with the formation of a sand boil at the leeward side of the levee, and has been frequently observed to proceed upstream along the base of the levee through a slit formation. The issue of most important concern is to estimate the critical head that could promote the occurrence of piping. Considering the flow through porous media and coupling it with Bernoulli’s equation and a critical tractive stress condition, a model is developed for the critical head. Using appropriate transformations, the proposed model takes on a form which supports Bligh’s empirical findings. Another model based on critical velocity is also developed to estimate the critical head. The functional form of these two models is evaluated using the critical head versus porosity data from a number of laboratory studies conducted in the Netherlands. These models were found to perform better than did Terzaghi’s model.     

Analytical Construction of Transient Flow Nets in Homogeneous and Isotropic Flow Medium

The purpose of this study is to construct time-dependent flow nets, also called transient flow nets in homogenous and isotropic flow medium. Transient flow nets under hydraulic structures are developed in response to reservoir head fluctuations. An analytical solution for a transient flow net has not been reported in the literature. Time-dependent flow net equations are limited in engineering applications to simple boundary conditions. The geometry of transient flow nets does not change with time, as only the numerical values assigned to equipotential lines and flow lines change with time.     

钢管水压试验机结构现状及发展趋势

钢管水压试验机是用来对钢管进行综合检查的设备,在冶金企业中是必不可少的。介绍了钢管水压试验机的系统组成,并从进出料形式、密封形式、增压形式分析了水压机的典型结构。针对水压试验机的未来发展趋势做了简要的分析。     

Seepage to a Drainage Ditch and Optimization of Its Shape

An optimal shape design problem for an empty drainage ditch is solved and it is shown that a semicircle intercepting saturated seepage from two constant potential rays is a contour of constant Darcian velocity and of maximal excavated volume at a given flow rate and ditch width. The corresponding family of isobars belongs to the class of conchoids of Nicomedes. The optimal flow is generated by a hydrodynamic dipole placed in a gravitational field.     

Revisited Analysis of Pressure Drop in Flow through Crushed Rocks

Experimental data of pressure drop in flow through crushed rocks are reanalyzed with the capillary model in comparison with a model based on the square root of permeability as characteristic length. The capillary model is described by two parameters: the pore diameter and the tortuosity. The comparison leads to relationships between the structural parameters, Reynolds number, and friction factor of each model. The interest of the capillary model is that a single equation can predict all the experimental data expressed in terms of a pore friction factor as a function of pore Reynolds number. The equation, which is the sum of a viscous term and an inertial one, is valid for the whole Reynolds number domain. The equation can be used for the determination of the limits of the Darcy and turbulent flow regimes. According to the criterion used to neglect the viscous or the inertial term, the flow regimes limits can be expressed by a simple numerical value.