Emitter Spacing Research Articles

Subsurface Drip Irrigation Emitter Spacing Effects on Soil Water Redistribution, Corn Yield, and Water Productivity

Emitter spacings of 0.3 to 0.6 m are commonly used for subsurface drip irrigation (SDI) of corn on the deep, silt loam soils of the U.S. Great Plains. Subsurface drip irrigation emitter spacings of 0.3, 0.6, 0.9 and 1.2 m were examined for the resulting differences in soil water redistribution, corn grain yield, yield components, seasonal water use, and water productivity in a 4-year field study (2005 through 2008) at the Kansas State University Northwest Research-Extension Center, Colby, Kansas.

Comparing soil moisture under trickle irrigation modeled as a point and line source

Abstract The validity of the assumption that an irrigation event from point sources can be approximated as an infinite line source is investigated in this article. This is accomplished by comparing soil water dynamics under line and point sources. Two existing mathematical models which simulate point and line drip irrigation were used. The models consider root water uptake, evaporation of soil water from the soil surface and incorporate hysteresis in the soil water characteristic curve. The comparison was made for two soil types (loamy sand and silt). The results showed that the treatment of a point source as a line source underestimates the water content values for both the soil types. This difference decreases when the depth of comparison increases. For soil depths greater than 30 cm and for time greater than irrigation duration the two models gave very close results. For the same emitter spacing and for the horizontal direction perpendicular to the drip line on the emitter spot, when the distance from the point and the line sources increases the difference of water content values increases. On the contrary, in the direction parallel to the drip line when the distance from the emitter increases (the distance from the line source remains the same) the difference of water content decreases. Lastly, differences are greater in the case of coarse grained soil than in fine grained soil.

Modelling of the influence of interelectronic interaction on the stationary characteristics of a resonant tunnel diode with spacer layers

The influence of the interelectronic interaction on the stationary characteristics of a resonant tunnel diode (RTD) with spacer layers (spacers) is investigated by means of a self-consistent solution to Schrodinger and Poisson equations. It is demonstrated that the interelectronic interaction influences significantly the RTD voltampere characteristics, in particular, it decreases the peak current density and displaces the position of maxima of the peak current dependence on the emitter spacer size. It is also demonstrated that the hysteresis of the RTD volt-ampere characteristics vanishes for definite spacer sizes.

Total energy loss assessment for trickle lateral lines equipped with integrated in-line and on-line emitters

The accurate evaluation for the pressure head distribution along a trickle (drip) irrigation lateral, which can be operated under low-pressure head, dictates to precisely determine the total energy (head) losses that incorporate the combined friction losses due to pipe and emitters and, the additional local losses, sometimes called minor losses, due to the protrusion of emitter barbs into the flow. In routine design applications, assessment of total energy losses is usually carried out by assuming the hypothesis that minor losses can be neglected, even if the previous experimental studies indicated that minor losses can become a significant percentage of total energy losses as a consequence of the high number of emitters (with reducing the emitter spacing) installed along the lateral line. In this study, first, simple mathematical expressions for computing three energy loss components—minor friction losses through the path of an integrated in-line emitter, the local pressure losses due to emitter connections, and the major friction losses along the pipe—are deduced based on the backward stepwise procedure, which are quickly implemented in a simple Excel spreadsheet, to rapidly evaluate the relative contribution of each energy loss component to the amount of total energy losses. An approximate combination formulation is finally proposed to evaluate total energy drop at the end of the lateral line. For practical purpose, two design figures were also prepared to demonstrate the variation of total friction losses (due to pipe and emitters) with emitter local losses, and the variation of pipe friction losses with emitter minor friction losses, versus different emitter spacing ranging from 0.2 to 1.5 m, and various total number of emitters, regarding two kinds of the integrated in-line emitters. Comprehensive comparison test covering two design applications for different kinds of integrated in-line and on-line emitters indicated that the present mathematical model is simple, can be easily adaptable, but sufficiently accurate in all design cases examined, in comparison with the alternative procedures available in the literature.

Integrated Emitter Local Loss Prediction Using Artificial Neural Networks

This paper describes an application of artificial neural networks (ANNs) to the prediction of local losses from integrated emitters. First, the optimum input-output combination was determined. Then, the mapping capability of ANNs and regression models was compared. Afterwards, a five-input ANN model, which considers pipe and emitter internal diameter, emitter length, emitter spacing, and pipe discharge, was used to develop a local losses predicting tool which was obtained from different training strategies while taking into account a completely independent test set. Finally, a performance index was evaluated for the test emitter models studied. Emitter data with low reliability were removed from the process. Performance indexes over 80% were obtained for the remaining test emitters.

MATHEMATICAL MODEL FOR MICRO-IRRIGATION DESING FOR CENTER PIVOT CORNERS

A mathematical model was developed to analyzing hydraulic characteristics in a micro-irrigation system design micro-irrigation system for center pivot corners. Different shape division (square, rectangular and approximately triangular shape) for center pivot corner, pipe diameters and lengths of lateral and telescopic manifold pipe with uniform slopes were studied. The model divided the center pivot corner into subunits micro-irrigation system (parts) and estimated lateral and emitter discharges and pressure head distribution along a lateral and manifold starting from the downstream as well as uniformity calculation. The friction head loss between successive emitters, laterals and manifold were also estimated using the Darcy-Weisbach formula. The model for designing manifold was run successfully for supplying water to one or two-side laterals. Field studies were undertaken to test the validity of the mathematical model for (EU), (UC), (QVAR) and (HVAR). Emission flow and pressure distributions were measured and compared quite well with those predicted from the model. The results indicated that, for approximately triangular shape part 1 for center pivot radius 450 m, outside lateral diameter 16 mm, lateral spacing 1.0 m and emitter spacing 0.5 m, average emitter discharge per lateral for 76 lateral were ranged from 3.618 to 3.766 l/h,. Lateral dynamic head increased from 0.81 to 1.26 bar for 76 lateral, (UC), increased by 7.42% and (UC) increased with decreasing lateral friction losses, Inlet lateral discharge for 76 laterals were ranged from 7.1 to 240.6 l/h for minimum (2 m) and maximum (63 m) lateral lengths, respectively. The model has been verified under different three center pivot radiuses (270, 359 and 450 m), which have same lateral diameter (16 mm), emitter spacing 1.0 m, lateral spacing 2.5 m and same in-line emitter discharge equation q=4.02H0.5 as an example for grape cultivation. Also, three different outside lateral diameters 16, 18 and 20 mm which, has same emitter spacing 0.5 m, lateral spacing 1.0 m and the same emitter type with constant center pivot radius (450 m) were verified for strawberry cultivation. In comparison between model output results of center pivot corner with R=450 m for lateral diameters 18 and 20 mm, it is clear that the number of parts dose not changed (13 parts) and total manifold discharge was equal to 313.46 (m3/h) for both lateral diameters. While, number of parts was (19 parts).for lateral diameters 16 mm. QVAR at lateral diameter 18 and 20 mm were ranged from 0.7 to 6.51% and 0.47 to 4.35% respectively. Also, HVAR were ranged from 1.14 to12.59% and 0.94 to 8.52% respectively. However, lateral diameter 20 mm was more effective in improving (QVAR) and (HVAR). In case of R=450 m for lateral diameters 16 mm, manifold diameters 50, 63, 75 and 90 mm versus lengths were 641, 185, 97 and 92 m respectively, while, manifold length were 505, 182, 91 and 158 m for lateral diameters 18 mm.

Structure optimization of multi-finger power SiGe HBTs for thermal stability improvement

The two-dimensional temperature profile of a power SiGe HBT with traditional uniform emitter finger spacing is calculated, which shows that there is a higher temperature in the central region of the device. With the aid of the theoretical analysis, an optimized structure of the HBT with non-uniform emitter finger spacing is presented. The peak temperature is lowered by 23.82 K, and the thermal resistance is also improved by 15.09% compared with that of the uniform one. The improvements above are ascribed to the increasing the spacing between fingers, and hence suppressing the heat flow from adjacent fingers to the center finger. Based on the analytical results, two types of HBTs with uniform emitter finger spacing and non-uniform emitter finger spacing are fabricated and their temperature profiles and thermal resistance are measured. The measured results agree well with the calculated results, verifying the accuracy of the calculations. For the HBT with non-uniform emitter finger spacing, the peak temperature and the thermal resistance are improved markedly over a wide biasing range compared with that of the uniform one. Therefore, both the calculated results and the experimental results verify that the optimized structure of power HBT with non-uniform emitter finger spacing is superior to the uniform emitter spacing structure for enhancing the thermal stability of power devices over a wide biasing range.

BEAM DYNAMICS OPTIMIZATION FOR THE XFEL PHOTO INJECTOR

The main challenge for the European XFEL photo injector is the production of 1 nC electron beams with a normalized transverse emittance of 0.9 mm mrad. The photo injector setup consists of a 1.5-cell L-band rf gun cavity supplied with solenoids for beam focusing and emittance compensation and the first accelerating section with 8 TESLA superconducting cavities. The first 4 cavities are used as a booster to provide by proper choice of its position, gradient and phase matching conditions for the emittance conservation. For optimization of the beam dynamics in the photo injector, a staged algorithm, based on ASTRA simulations, has been developed. The first stage considers the emission of electrons from a photo cathode. The cathode laser energy and its transverse parameters are adjusted to produce a bunch charge of 1 nC in presence of space charge forces (including image charge at the cathode) and Schottky-like effects. The second stage contains rf gun cavity and solenoid optimization. The booster position, gradient and initial phase are optimized at the third stage yielding the minimum emittance at the photo injector exit. Results of the XFEL photo injector optimization will be presented. Besides simulations experimental studies towards XFEL photo injector are carried out. The photo injector test facility at DESY in Zeuthen (PITZ) develops photo injectors for FELs, including FLASH and the European XFEL. A thorough comparison of measured data with results of beam dynamics simulations is one of the main PITZ goals. Detailed experimental studies on photo emission processes, thermal emittance, transverse and longitudinal phase space of the electron beam are being performed together with beam dynamics simulations. This aims to result in better understanding of beam dynamics in high brightness photo injectors. Experimentally obtained photo injector characteristics (like thermal emittance) have to be used in an additional optimization of the photo injector resulting in more realistic beam dynamics simulations. Results of these studies will be reported as well.

High resolution energy analyzer for broad ion beam characterization

Characterization of the ion energy distribution function (IEDF) of low energy high current density ion beams by conventional retarding field and deflection type energy analyzers is limited due to finite ion beam emittance and beam space charge spreading inside the analyzer. These deficiencies are, to a large extent, overcome with the recent development of the variable-focusing retarding field energy analyzer (RFEA), which has a cylindrical focusing electrode preceding the planar retarding grid. The principal concept of this analyzer is conversion of a divergent charged particle beam into a quasiparallel beam before analyzing it by the planar retarding field. This allows analysis of the beam particle total kinetic energy distribution with greatly improved energy resolution. Whereas this concept was first applied to analyze 5-10 keV pulsed electron beams, the present authors have adapted it to analyze the energy distribution of a low energy (<or=1 KeV) broad ion beam. In this paper we describe the RFEA design, which was modified from the original, mainly as required by the specifics of broad ion beam energy analysis, and the device experimental characterization and modeling results. Among the modifications, an orifice electrode placed in front of the RFEA provides better spatial resolution of the broad ion beam ion optics emission region and reduces the beam plasma density in the vicinity of analyzer entry. An electron repeller grid placed in front of the RFEA collector was found critical for suppressing secondary electrons, both those incoming to the collector and those released from its surface, and improved energy spectrum measurement repeatability and accuracy. The use of finer mesh single- and double-grid retarding structures reduces the retarding grid lens effect and improves the analyzer energy resolution and accuracy of the measured spectrum mean energy. However, additional analyzer component and configuration improvements did not further change the analyzed IEDF shape or mean energy value. This led us to conclude that the optimized analyzer construction provides an energy resolution considerably narrower than the investigated ion beam energy spectrum full width at half maximum, and the derived energy spectrum is an objective and accurate representation of the analyzed broad ion beam energy distribution characteristics. A quantitative study of the focusing voltage and retarding grid field effects based on the experimental data and modeling results have supported this conclusion.

Nanoelectrospray Emitter Arrays Providing Interemitter Electric Field Uniformity

Arrays of electrospray ionization (ESI) emitters have been reported previously as a means of enhancing ionization efficiency or signal intensity. A key challenge when working with multiple, closely spaced ESI emitters is overcoming the deleterious effects caused by electrical interference among neighboring emitters. Individual emitters can experience different electric fields depending on their relative position in the array, such that it becomes difficult to operate all of the emitters optimally for a given applied potential. In this work, we have developed multi-nanoESI emitters arranged with a circular pattern, which enable the constituent emitters to experience a uniform electric field. The performance of the circular emitter array was compared to a single emitter and to a previously developed linear emitter array, which verified that improved electric field uniformity was achieved with the circular arrangement. The circular arrays were also interfaced with a mass spectrometer via a matching multicapillary inlet, and the results were compared with those obtained using a single emitter. By minimizing interemitter electric field inhomogeneities, much larger arrays having closer emitter spacing should be feasible.

New Computational Fluid Dynamic Procedure to Estimate Friction and Local Losses in Coextruded Drip Laterals

The design of trickle irrigation systems is crucial to optimize profitability and to warrant high values for the emission uniformity (EU) coefficient. EU depends on variation of the pressure head due to head losses along the lines and elevation changes, as well as the water temperature, and other parameters related to the emitters (manufacturer’s coefficient of variation, number of emitters per plants, emitter spacing). Trickle irrigation plants are usually designed using small diameter plastic pipes (polyethylene or polyvinyl chloride). The design problem, therefore, needs to consider head losses along the lines as well as emitter discharge variations due to the manufacturer’s variability. Variations in the hydraulic head are a consequence of both friction losses along the pipe and local losses due to the emitters’ connections, whose importance has been recently emphasized. Since each local loss depends on the emitter type (in-line or on-line) as well as on its shape and dimensions, the morphological variability of the commercially available emitter requires experimental investigations to determine local losses in drip laterals. On the other hand, local losses can be estimated by the mean of computational fluid dynamics (CFD) models, allowing analysis of velocity profiles and the turbulence caused by the emitters’ connections. FLUENT software can be considered a powerful tool to evaluate friction and local losses in drip irrigation laterals, after the necessary validation has been carried out by means of experimental data. The main objective of this study was to assess a CFD technique to evaluate friction and local losses in laterals with in-line coextruded emitters. The model was initially used to choose the turbulence model allowing the most accurate estimation of friction losses in small diameter polyethylene pipes, characterized by low Reynolds number. Second, the possibility of using CFD to predict local losses in drip irrigation laterals with a commercially available coextruded emitter was investigated. Simulated local losses were obtained as difference of the total and friction losses along a trunk of pipe, where one single emitter was installed, not considering the emitter outflow. The proposed procedure allows to evaluate local losses for other different emitter models, avoiding tedious and time-consuming experiments.

Dual Electrospray Ion Source for Electron-Transfer Dissociation on a Hybrid Linear Ion Trap−Orbitrap Mass Spectrometer

A dual electrospray ionization source (ESI) has been modified to simultaneously produce cations and anions, one from each emitter, for performing rapid electron-transfer dissociation (ETD) ion/ion reactions on a hybrid linear ion trap-orbitrap mass spectrometer. Unlike the pulsed dual ESI sources that were used to generate ETD reagent ions, this source separates the emitters in space, rather than time, by physically switching which one is in front of the atmospheric inlet. The new arrangement allows for substantially enhanced spray stability and decreased switching times (<or=30 ms), allowing for more tandem-MS spectra per unit time. Herein, we demonstrate the stability of the ETD anion population and the ability to identify several c- and z-type product ions from multiply protonated peptide cations.

Optimisation of trench isolated bipolar transistors on SOI substrates by 3D electro-thermal simulations

This paper provides a comprehensive analysis of thermal resistance of trench isolated bipolar transistors on SOI substrates based on 3D electro-thermal simulations calibrated to experimental data. The impact of emitter length, width, spacing and number of emitter fingers on thermal resistance is analysed in detail. The results are used to design and optimise transistors with minimum thermal resistance and minimum transistor area.

Experimental and theoretical study of a cone-jet for an electrospray microthruster considering the interference effect in an array of nozzles

The interference effect on an array of electrospray emitters is analytically and experimentally investigated. An analytical model is presented to predict the behavior of the operating voltage with respect to emitter spacing in an array of emitters. The basic idea of these models is to superimpose the electric potential of individual emitters together in an array of emitters. If only one of the emitters operates and no liquid is supplied through the neighboring emitters, the potential required to form a stable cone-jet generally increases as the emitters move closer to each other due to electrical shielding. However, at very close spacing the required potential decreases. If all the emitters operate simultaneously, the operating voltage required for cone-jet spraying increases as the emitter spacing decreases; furthermore, there is no decrease in potential when the spacing is very close. The results of the analytical electrostatic interference model agree well with the experimental data.

Using HYDRUS-2D Simulation Model to Evaluate Wetted Soil Volume in Subsurface Drip Irrigation Systems

Drip irrigation is considered one of the most efficient irrigation systems. Alternatively to the traditional drip irrigation systems, laterals can be installed below the soil surface. Realizing the subsurface drip irrigation (SDI), which recently has been increasing in use as a consequence of advances in plastics technology, making SDI equipment more affordable and long lasting. Due to its potential high efficiency SDI may produce benefits, especially in places where water is a limited source. As the use of SDI is relatively new, a better understanding of the infiltration process around a buried point source can contribute to increased water use efficiency and consequently the success of drip irrigation system. In addition, proper design and management of such a system needs the judicious combination of drip spacing, discharge rates, irrigation duration and time interval between consecutive irrigations. To this aim, numerical models can represent a powerful tool to analyze the evolution of the wetting pattern during the distribution and redistribution processes, in order to explore SDI management strategies, to set up the duration of irrigation, and finally to optimize water use efficiency. In the paper the suitability of the HYDRUS-2D simulation model is verified, at the scale of a single emitter, on the basis of experimental observations, with the aim to assess the axis-symmetrical infiltration process consequent to subsurface drip irrigation. The model was then applied in order to evaluate the main dimensions of the wetted soil volume surrounding the emitter during irrigation as a function of time and initial soil water content. The investigation, carried out in a sandy-loam soil, showed the suitability of the model to well simulate infiltration processes around an emitter during irrigation. Model application allowed also, for the examined soil, to evaluate the emitter spacing accounting for the maximum soil depth to irrigate.

Subsurface drip irrigation of onions: Effects of drip tape emitter spacing on yield and quality

Improved irrigation water use efficiency is an important component of sustainable agricultural production. Efficient water delivery systems such as subsurface drip irrigation (SDI) can contribute immensely towards improving crop water use efficiency and conserving water. However, critical management considerations such as choice of SDI tube, emitter spacing and installation depth are necessary to attain improved irrigation efficiencies and production benefits. In this study, we evaluated the effects of subsurface drip tape emitter spacing (15, 20 and 30 cm) on yield and quality of sweet onions grown at two locations in South Texas—Weslaco and Los Ebanos. Season-long cumulative crop evapotranspiration (ETc) was 513 mm in Weslaco and 407 mm at Los Ebanos. Total crop water input (rain + irrigation) at Weslaco was roughly equal to ETc (92% ETc) whereas at Los Ebanos, water inputs exceeded ETc by about 35%. Onion yields ranged from 58.5 to 70.3 t ha −1 but were not affected by drip tube emitter spacing. Onion pungency (pyruvic acid development) and soluble solids concentration were also not significantly influenced by treatments. Crop water use efficiency was slightly higher at Weslaco (13.7 kg/m 3) than at Los Ebanos (11.7 kg/m 3) partly because of differences in total water inputs resulting from differences in irrigation management. The absence of any significant effects of drip tape emitter spacing on onion yield may be due to the fact that irrigation was managed to provide roughly similar irrigation amounts and optimum soil moisture conditions in all treatments.

Water Movement in Mulched Beds in Rocky Soils of Miami-Dade County

HS-1059, a 6-page fact sheet by David Studstill, Eric Simonne, Teresa Olczyk, Rafael-Munoz Carpena, presents the results of a study of flow rates on calcareous soils using dyes to observe the movement of water in the beds under various flow rates and emitter spacings. Published by the UF Horticultural Sciences Department, March 2006. HS1059/HS313: Water Movement in Mulched Beds in Rocky Soils of Miami-Dade County (ufl.edu)

Improvement of saline water use under drip irrigation system

The use of saline water in a surface drip irrigation system has several advantages over other irrigation methods. Variables affecting soil water content ( θ w) and soil salinity (EC w), including irrigation regimes and crop growth stages, were investigated at different radial distances from the emitter at a depth of 10 cm. Three irrigation regimes were applied: the first irrigation regime (ET c) was based on daily crop–water requirement while the two others were based on ET c + 20% and + 40% (1.2ET c and 1.4ET c, respectively). The simultaneous distribution of θ w and EC w under drip irrigation was measured by time domain reflectometry (TDR). The results indicated that EC w increased in the order ET c > 1.2ET c > 1.4ET c and also with crop growth stages. For all the irrigation regimes and all crop growth stages, the maximum θ w and minimum EC w occurred simultaneously at a radial distance of 10 cm ( r 10) from the emitter. The simultaneous occurrence of maximum θ w and minimum EC w at the 20 cm radial distance from emitter ( r 20) was noted only for 1.4ET c. It is suggested that irrigation should commence at different times before noon, depending on the crop growth stage, so that maximum θ w (minimum EC w) will coincide with maximum evapotranspiration (ET o). The influence of θ w on EC w was restricted to a small radius of about 0–20 cm from the emitter. Beyond this range, increases in θ w did not significantly affect EC w. The first irrigation regime (ET c) was found unsuitable for irrigation with saline water. Emitter spacing of 25 and 30 cm were suggested for 1.2ET c and 1.4ET c to minimize EC w levels along the lateral pipe. Based on the crop–water production function the yield reduction due to saline water use was minimum under 1.4ET c, which cannot be improved by increasing the amount of irrigation water.

Simulation technology to support base metal ore heap leaching

A simulation framework is outlined for the analysis of the operation of both the heap and the associated water balance circuit for the leaching of primary metal ores. The heap simulation is based on a detailed computational model of the leaching process. The process chemistry, including reactants in the gas–liquid–solid matrix, gas flow, variably saturated liquid flow, species transport in both phases, heat transport, and biomass growth and catalysis, is accounted for in models that are equally applicable to simple and complex geometries. The leaching models are contained within the PHYSICA computational modelling environment that includes a powerful multiphase computational fluid dynamic (CFD) solver enabling reactive flow simulation through arbitrarily complex geometries. Tools have been developed in one-, two- and three-dimensions to capture a variety of aspects of the leaching process behaviour. By careful choice of tools, the framework can be applied to a wide range of leaching problems from small scale (e.g. analysis of column tests and drip emitter spacing) through to full scale heap simulation. An optimised version of the heap leach model is itself embedded within a simulation environment that exploits the BILCO mass balance software to enable dynamic simulation of the water balance within the whole plant circuit.

Analytical Expressions for Hydraulic Calculation of Trapezoidal Drip Irrigation Units

Analytical expressions have been developed relating water distribution indexes in trapezoidal drip irrigation units to design variables which define these units: lengths and diameters of pipes, emitter and lateral spacing, slopes, emitter flow equation parameters, and equivalent lengths characterizing local losses. The proposed expressions are founded in classical hydraulics. They are more accurate than predictions in irrigation practice and are easier to handle than the simulation models frequently proposed to irrigation technicians. Unit design and irrigation decision making and evaluation can thus be furthered. An example for the application of the proposed expressions is presented. First, lateral and submain diameters are determined for different shapes of irrigation units to achieve a given water application uniformity. The irrigation time to supply the desired irrigation depth is then calculated. Results are finally compared with values obtained by simulations that take into account hydraulic and manufacture variations in the unit.