scholarly journals Slope Effects on the Pressure Head Profile Patterns of Sprinkler Irrigation Laterals, I. Theoretical Analysis

2018 ◽  
Vol 07 (03) ◽  
Author(s):  
Zerihun D ◽  
Sanchez CA ◽  
Bautista E
Keyword(s):  
Theoretical Analysis ◽  
Sprinkler Irrigation ◽  
Pressure Head

Effects of Blade Wrap Angle Influencing a Pump as Turbine

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Sun-Sheng Yang ◽  
Fan-Yu Kong ◽  
Hao Chen ◽  
Xiang-Hui Su
Keyword(s):  
Theoretical Analysis ◽  
Pressure Head ◽  
Hydraulic Loss ◽  
Impeller Blade ◽  
Loss Distribution ◽  
Performance Change ◽  
Shaft Power ◽  
Wrap Angle ◽  
Specific Speed ◽  
Blade Wrap Angle

A pump is not ideally designed to operate as a turbine. To improve the efficiency of a pump as turbine (PAT), the redesign of the PAT, according to the flow of the turbine, is required. The blade wrap angle is one of the main geometric parameters in impeller design. Therefore, an investigation into the blade wrap angle to the PAT’s influence can be useful. In order to understand blade wrap angle to the influence of the PAT, this paper numerically investigated three different specific speeds of PATs with different blade wrap angles. The validity of numerical simulation was first confirmed through a comparison between numerical and experimental results. The performance change of the PATs with the blade wrap angle was acquired. A detailed hydraulic loss distribution and a theoretical analysis were performed to investigate the reasons for performance changes caused by the blade wrap angle. The results show that there is an optimal blade wrap angle for a PAT to achieve the highest efficiency and the optimal blade wrap angle decreases with an increasing specific speed. A performance analysis shows the PAT’s flow versus pressure head (Q-H) and flow versus generated shaft power (Q-P) curves are lowered with the decrease of the blade wrap angle. The hydraulic loss distribution and theoretical analysis illustrate that it is the decrease of hydraulic loss within the impeller, together with the decrease of the theoretical head, that results in the performance decrease. The decrease of hydraulic loss within the impeller is attributed to the shortened impeller blade passage and the reduced velocity gradient within the impeller flow channel. With the decrease of the blade wrap angle, the slip factor of the PAT’s impeller is decreased; therefore, its theoretical head is also decreased.

scholarly journals The Development of a Calculation Model for the Instantaneous Pressure Head of Oscillating Water Flow in a Pipeline

Water ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1583 ◽  
Author(s):  
Kai Zhang ◽  
Bo Song ◽  
Delan Zhu
Keyword(s):  
Water Flow ◽  
Relative Error ◽  
Water Distribution ◽  
Irrigation System ◽  
Complex Function ◽  
Sprinkler Irrigation ◽  
Pressure Head ◽  
Calculation Model ◽  
Maximum Relative Error ◽  
Instantaneous Pressure

Sinusoidal oscillating water flow at low pressure can improve the anti-clogging ability of an emitter in drip irrigation or the water distribution of a nozzle in sprinkler irrigation and reduce the cost and energy consumption of the irrigation system. In this study, the characteristics of instantaneous pressure head attenuation of oscillating water flow along a pipeline have been investigated. By using a complex function to solve the continuity equation and the momentum equation of a pipeline with water hammer motion and using the Darcy–Weisbach formula to estimate the head loss, a calculation model for the instantaneous pressure head of oscillating water flow along a pipeline was developed. The measured value of the amplitude of the pressure head and the average instantaneous pressure head in the experiments have been used to verify the corresponding pressure head calculated by the model. The results show that the amplitude of the pressure head and the average instantaneous pressure head decrease linearly along the pipeline. The calculated value of the amplitude of the pressure head and the average instantaneous pressure head are basically close to the corresponding measured pressure head. From the results of all the tests, the maximum relative error of the calculated and measured value of the amplitude of the pressure head along the pipeline was 9.44%. The maximum relative error of the calculated and measured value of the average instantaneous pressure head along the pipeline was 8.37%. Hence, the model can accurately predict the instantaneous pressure head of oscillating water flow along a pipe and provide a theoretical basis for the application of oscillating water flow in irrigation systems and the design of irrigation pipe networks.

scholarly journals Calidad del riego por aspersión subfoliar en cacao (Theobroma cacao L.) en la finca San Vicente, Los Ríos, Ecuador

2018 ◽  
pp. 1
Author(s):  
Juan Tandazo Garcés ◽  
Oscar Caicedo Camposano ◽  
Carlos Salas Macías ◽  
Viviana Sánchez Vásquez
Keyword(s):  
Theobroma Cacao ◽  
Irrigation System ◽  
Sprinkler Irrigation ◽  
Pressure Head ◽  
Uniformity Coefficient ◽  
Coefficient Distribution ◽  
High Uniformity ◽  
Distribution Uniformity ◽  
Theobroma Cacao L

Quality of subfoliar sprinkler irrigation in Theobroma Cacao L. in San Vicente farm, Los Ríos, Ecuador Resumen Se realizó la evaluación del manejo de un sistema de riego por aspersión subfoliar en el cultivo de cacao, en donde el objetivo fue valorar su comportamiento hidráulico. Se estudiaron tres presiones de trabajo de los aspersores en cinco módulos del sistema. Los parámetros evaluados fueron: presiones al inicio y final de los laterales de riego, caudales en esos mismos sitios, coeficiente de uniformidad de Christiansen, uniformidad de distribución y área regada adecuadamente. Los resultados indican que existe una variación de presión y caudal por encima de lo teórico (20% y 10%). Se evidenció que altos coeficientes de uniformidad no representan la mayor área regada adecuadamente. Las presiones de trabajo estudiadas en los aspersores aseguran altos coeficientes de uniformidad del riego, no obstante, si lo que se desea es alcanzar la mayor área adecuadamente regada se debe operar a 275,79 kPa. Palabras claves: caudal; uniformidad; presión de trabajo. Abstract The evaluation of the management of a subfoliar sprinkler irrigation system in the cocoa crop was carried out, where the objective was to evaluate its hydraulic behavior. Three working pressures of the sprinklers were studied in five modules of the system. The parameters evaluated were: pressures at the beginning and end of the irrigation sides flow at those same sites, Christiansen Uniformity Coefficient, Distribution Uniformity and Adequately Irrigated Area. The results indicate that there is a variation of pressure and flow above the theoretical, that is, of 20% and 10%. It was evidenced that high uniformity coefficients do not represent the largest area irrigated adequately. The work pressures studied in the sprinklers ensure high coefficients of uniformity of irrigation, however, if what is desired is to reach the largest area adequately irrigated, it should be operated at 275.79 kPa. Keywords: flow; uniformity; pressure head.

scholarly journals Analysis of Saturation Risk in Sprinkler Irrigation: Case of Cherfech Irrigation Perimeter in Tunisia

2018 ◽  
Vol 10 (2) ◽  
pp. 130
Author(s):  
Samir Yacoubi ◽  
Adel Slatni ◽  
Khemaies Zayani
Keyword(s):  
Sprinkler Irrigation ◽  
Pressure Head ◽  
Field Trials ◽  
Application Rate ◽  
Wetting Front ◽  
Saturated Water Content ◽  
M 12 ◽  
Disc Infiltrometer ◽  
Good Agreement

This study is targeted to the assessment of the saturation risk in sprinkler irrigation. For this purpose, in situ field trials were carried out to infer the saturated hydraulic conductivity (Ks) and sorptivity (S) using the disc infiltrometer method. Since the measured values of Ks are very close to prescribed application rate, caution is required. In a first step, the pressure head at the wetting front (hf) and the useful porosity (θs – θi) are assumed to be constant. Thus, the logarithmic derivation of the sorptivity provides a relation between relative variations of S and Ks. The ponding time (Ts) is estimated from Green and Ampt (1911) and Philip (1957b) infiltration equations. The risk of saturation is deemed to be inexistent inasmuch as simulated values of Ts are greater than the irrigation times practiced in the zone. In a second step, the values of the pressure head at the wetting front and saturated water content were assumed to be variable with soil texture. Simulations of the ponding time were carried out based on Rawls and al. (1981) data. For the recommended sprinkler spacing in the Cherfech perimeter (12 m × 12 m), the simulations show a good agreement between Ts values generated from Green and Ampt and Philip equations for Ks ranging from 1.5 to 6 mm/h. Moreover, it was established that saturation risk due to a gradual texture variation is virtually inexistent in the conditions prevailing in Cherfech perimeter.

scholarly journals Wind Drift Evaporation Loss and Soil Moisture Distribution under Sprinkler Irrigated Blackgram (Vigna mungo L.)

2021 ◽  
Vol 12 (6) ◽  
pp. 731-736
Author(s):  
K. Arunadevi ◽  
◽  
I. Nongkynrih ◽  
J. Ramachandran ◽  
◽  
...  
Keyword(s):  
Soil Moisture ◽  
Wind Speed ◽  
Sprinkler Irrigation ◽  
Pressure Head ◽  
Sprinkler System ◽  
Moisture Distribution ◽  
Wind Drift ◽  
Uniformity Coefficient ◽  
Evaporation Loss ◽  
Soil Moisture Distribution

An experiment was conducted during March–June 2018 with the sprinkler irrigation system covered in an area of 39×42 m2. Proper design and management of sprinkler irrigation systems improves the uniformity of moisture distribution and reduces wind drift and evaporation losses (WDEL) for effective crop growth. Uniformity coefficient, wind drift and evaporation loss of the sprinkler system at a different pressure head of 2 kg cm-2, 2.5 kg cm-2 and 3 kg cm-2 were studied. Wind speed was observed by using handheld anemometer. The wind speed ranged between 0.9 to 4.5 m s-1. The highest uniformity coefficient of 88.19% and wind drift and evaporation loss of 3.5% were obtained at the pressure head of 3 kg cm-2 and the wind speed of 0.9 m s-1. Soil samples were collected at different depths of 0–10 cm, 10–20 cm, 20–30 cm and at a radial distance from 0 m, 3 m, 6 m, 9 m, 12 m respectively to determine the soil moisture distribution pattern. The soil moisture content values were plotted by using the computer software, surfer 10 of the windows version and contour maps were drawn. The moisture content was found to be more at 0–10 cm depth, as compared to 10–20 cm and 20–30 cm depth. The percentage of moisture was found to be highest at a 6 m distance, which was due to overlapping of the sprinkler system.

Microdiffraction Patterns of Small Metallic Particles II; Theoretical Analysis

1982 ◽  
Vol 40 ◽  
pp. 668-669
Author(s):  
A. Gómez ◽  
P. Schabes-Retchkiman ◽  
M. José-Yacamán ◽  
T. Ocaña
Keyword(s):  
Experimental Data ◽  
Electron Diffraction ◽  
Theoretical Analysis ◽  
Size Range ◽  
Dynamical Theory ◽  
Metallic Particles ◽  
Splitting Effect

The splitting effect that is observed in microdiffraction pat-terns of small metallic particles in the size range 50-500 Å can be understood using the dynamical theory of electron diffraction for the case of a crystal containing a finite wedge. For the experimental data we refer to part I of this work in these proceedings.

Theoretical analysis of a monopole antenna with conducting flat disk above the earth

2001 ◽  
Vol 84 (7) ◽  
pp. 27-36
Author(s):  
Aki Yuasa ◽  
Daisuke Itatsu ◽  
Naoki Inagaki ◽  
Nobuyoshi Kikuma
Keyword(s):  
Theoretical Analysis ◽  
Monopole Antenna ◽  
The Earth ◽  
Flat Disk

Context Aversion, Pavlovian Conditioning, and the Psychological Side Effects of Chemotherapy

1997 ◽  
Vol 2 (2) ◽  
pp. 118-124
Author(s):  
Geoffrey Hall
Keyword(s):  
Animal Model ◽  
Side Effects ◽  
Theoretical Analysis ◽  
Conditioned Response ◽  
Behavioral Strategies ◽  
Contextual Cues ◽  
Anticipatory Nausea ◽  
Laboratory Rats ◽  
Anticipatory Nausea And Vomiting ◽  
Parallel Case

Patients who have undergone several sessions of chemotherapy for cancer will sometimes develop anticipatory nausea and vomiting (ANV), these unpleasant side effects occurring as the patients return to the clinic for a further session of treatment. Pavlov's analysis of learning allows that previously neutral cues, such as those that characterize a given place or context, can become associated with events that occur in that context. ANV could thus constitute an example of a conditioned response elicited by the contextual cues of the clinic. In order to investigate this proposal we have begun an experimental analysis of a parallel case in which laboratory rats are given a nausea-inducing treatment in a novel context. We have developed a robust procedure for assessing the acquisition of context aversion in rats given such training, a procedure that shows promise as a possible animal model of ANV. Theoretical analysis of the conditioning processes involved in the formation of context aversions in animals suggests possible behavioral strategies that might be used in the alleviation of ANV, and we report a preliminary experimental test of one of these.

Sign in / Sign up

Export Citation Format

Share Document