1,721,002 research outputs found
Baffle sluice modules with improved performance
No full textThis work demonstrates the applicability of more generalized sluice gate equations to the design of baffle sluice modules. The generalized equations allow the module to be designed for any upstream head. These equations also offer additional understanding of the behavior of the baffle sluice module and demonstrate that the first baffle of the module is largely redundant. The constraint of having the minimum water level coincide with the crest of the first baffle has been removed. Through an optimization procedure, an alternative design method is suggested that will theoretically improve the performance of the baffle sluice module. Through this design technique, a module can be designed with any practical number of baffles. The effect of combined orifice-weir flow and width of the module is also discusse
Adjusted average correction factors for sprinkler laterals
No full textThis paper is the fourth in a series on friction factors for sprinkler laterals. The widely used friction correction factor F was developed by Christiansen for the hydraulic analysis of sprinkler laterals. A significant modification to this factor was the adjusted friction correction factor Fa. The adjusted friction correction factor can be used when the first sprinkler is a fraction of a full spacing from the lateral inlet. To design laterals with outlets and outflow at the downstream end, friction correction factor G was developed with the corresponding adjusted friction correction factor Ga. To calculate the average pressure head along a lateral, the average correction factors FAVG and GAVG were developed. These average correction factors can be used where friction correction factors F and G are used to analyze a lateral. This paper introduces two final adjusted average correction factors FaAVG and GaAVG, which can be used to determine the average pressure head in laterals analyzed using Fa or Ga. Use of these factors is demonstrated in an example
Adjusted factor G(a) for pipelines with outlets and outflow
No full textThe adjusted factor Ga is a generic friction loss correction factor for pipelines with multiple outlets. The adjusted factor Ga can be applied to pipelines with or without outflow at the downstream end. Furthermore, this factor can be applied to a pipeline where the first outlet is at a full outlet spacing or a fractional outlet spacing from the pipeline inlet. When the outflow at the downstream end is reduced to zero, the adjusted factor Ga reduces to the adjusted factor Fa. If the first outlet is positioned one outlet spacing from the pipeline inlet, the factor Ga reduces to G. Finally, if both the outflow is zero and the first outlet is one outlet spacing from the pipeline inlet, the adjusted factor Ga reduces to a close approximation of the well known factor F. The adjusted factor Ga is a function of the number of outlets along the pipeline, the location of the first outlet from the pipeline inlet, the outflow ratio, and the velocity exponent of the head loss formula
Inlet pressure for horizontal tapered laterals
No full textThe adjusted factor Ga is a generic friction loss correction factor for pipelines with multiple outlets. The adjusted factor Ga can be applied to pipelines with or without outflow at the downstream end. Furthermore, this factor can be applied to a pipeline where the first outlet is at a full outlet spacing or a fractional outlet spacing from the pipeline inlet. When the outflow at the downstream end is reduced to zero, the adjusted factor Ga reduces to the adjusted factor Fa. If the first outlet is positioned one outlet spacing from the pipeline inlet, the factor Ga reduces to G. Finally, if both the outflow is zero and the first outlet is one outlet spacing from the pipeline inlet, the adjusted factor Ga reduces to a close approximation of the well known factor F. The adjusted factor Ga is a function of the number of outlets along the pipeline, the location of the first outlet from the pipeline inlet, the outflow ratio, and the velocity exponent of the head loss formula
Correction factors for center-pivots with end-guns
No full textThe end-gun discharge of center pivots is expressed as a ratio of the discharge at the pivot. Using this ratio, equations are developed for the friction correction factor and pressure distribution factor. If end-gun discharge is reduced to zero, then these equations reduce to the well-established equation for the friction correction factor and pressure distribution factor. For an end-gun ratio of unity, the friction correction factor also becomes unity, reflecting that the lateral is in fact a pipeline without outlets. The pressure distribution factor becomes linear, reflecting that head loss varies linearly with length. For a lateral of constant diameter and typical end- gun discharge there is a significant increase in head loss due to friction. However, there is insignificant difference in the estimate using either this technique or the effective radius technique. The pressure distribution factor is slightly higher, indicating that in laterals with end guns the pressure head toward the center of the lateral is higher. The equations presented can be used to design center-pivot laterals with end guns or the first segment of a tapered center pivot lateral
Factor "G" for pipelines with equally spaced multiple outlets and outflow
No full textA factor G for pipelines with equally spaced multiple outlets and outflow at the downstream end is derived. The proposed factor is a function of the number of outlets along the pipeline and also a function of the friction formula used. Factor G allows head loss in such pipelines to be computed directly provided the first outlet is one outlet spacing distance from the pipeline inlet. Under conditions of zero outflow at the downstream end of the pipeline, factor G reduces to the well known Christiansen’s factor F. Factor G allows the design of segments of pipelines with multiple outlets. It may find application with irrigation engineers in designing sprinkler and trickle irrigation laterals and manifolds with multiple diameter sizes. It also may be used in trickle line hydraulics in flushing mode
Friction correction factors for center-pivots
No full textAnalytical equations for friction correction factors for center-pivot laterals without end guns are developed. This work illustrates a discrepancy when earlier equations are applied to center-pivots with small numbers of outlets. Earlier equations were also limited to center-pivots with constant outlet spacing. Equations presented in the current work are developed for center-pivots with constant outlet spacing and also for center-pivots with constant outlet discharge. When the equations developed in the current work are applied to center-pivots with a large number of outlets, the results are in good agreement with previous work for center-pivot laterals with an infinite number of outlets. When applied to smaller number of outlets the equations presented here provide a more precise estimate of the friction correction factor. Using the current equations, the friction correction factor for center-pivots with constant outlet spacing was found to be very similar to the friction correction factor for center-pivots with constant outlet discharge. Useful simple equations are also presented for calculating the discharge of each outlet or for calculating the spacing between outlets
Design of hydraulically efficient power-law channels with freeboard
No full textA power law-channel is a generalized form of the parabolic channel. The exponent of the governing equation is a variable that for certain maximum permissible side slopes can be determined by maximizing the cross-sectional area of flow (or minimizing the wetted perimeter). Using this exponent rather than the constant allows a hydraulically more efficient open channel section to be designed. In earlier work on power law channels freeboard was neglected to simplify the analysis. However as pointed out by several authors, a channel without freeboard is of academic interest only and not practical. All open channels are in practice designed and constructed with freeboard as a factor of safety. In this paper freeboard has been introduced as an additional parameter to be taken into account when designing a power law channel. The work from this paper is applied to an earlier example of a parabolic channel to demonstrate a practical design
Irrigation scheduling I: Integer programming approach
No full textThis paper shows how a sequential irrigation schedule for a tertiary unit can be interpreted as a single machine scheduling problem with earliness, tardiness,and a common deadline. An integer program solution is presented for this irrigation scheduling problem. Two different models are presented to reflect different management options at the tertiary level. The first model allows jobs to be scheduled noncontiguously. In the second model only contiguous jobs are allowed. The second model has three submodels reflecting the various ways in which contiguous jobs can be scheduled over a fixed interval. Earlier work in determining unit costs of earliness/tardiness is reviewed and an alternative improved method is suggested. The models presented in this paper are applied to a tertiary unit With 16 users, both. as a single interval and multi-interval irrigation. scheduling problem.
An alternative integer program is also presented which although computationally more efficient can only be used for single period scheduling problems. The models developed in this paper can be used to solve small scheduling problems and also to calibrate the heuristics as presented in the companion paper
Irrigation scheduling with genetic algorithms
No full textA typical irrigation scheduling problem is one of preparing a schedule to service a group of outlets that may be serviced simultaneously. This problem has an analogy with the classical multimachine earliness/tardiness scheduling problem in operations research (OR). In previously published work, integer programming was used to solve irrigation scheduling problems; however, such scheduling problems belong to a class of combinatorial optimization problems known to be computationally demanding. This is widely reported in OR literature. Hence integer programs (IPs) can be used only to solve relatively small problems typically in a research environment where considerable computational resources and time can be allocated to solve a single schedule. For practical applications, metaheuristics such as genetic algorithms, simulated annealing, or tabu search methods need to be used. However, these need to be formulated carefully and tested thoroughly. The current research explores the potential of genetic algorithms to solve the simultaneous irrigation scheduling problem. For this purpose, two models are presented: the stream tube model and the time block model. These are formulated as genetic algorithms, which are then tested extensively, and the solution quality is compared with solutions from an IP. The suitability of these models for the simultaneous irrigation scheduling problem is reported.<br/
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