The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Delan Zhu - One of the best experts on this subject based on the ideXlab platform.
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Development and Sensitivity Analysis of an Empirical Equation for Calculating the Amplitude of Pressure Head Loss of Oscillating Water Flow in Different Types of Pipe
Water, 2020Co-Authors: Kai Zhang, Baoxu Zhang, Delan ZhuAbstract:Low Pressure oscillating water flow can reduce the investment and energy consumption of irrigation. It is also effective in reducing the clogging of an emitter and improving the spraying quality of sprinklers. In order to overcome the problem of the complex process in calculating the amplitude of the Pressure Head loss of oscillating water flow in different types of pipes, in this study, an empirical equation for the amplitude of the Pressure Head loss of oscillating water flow in different types of pipe has been developed. Further, validation experiments have been conducted to verify the accuracy of the calculated amplitudes of the Pressure Head loss by the empirical equation. The results show that average relative error between the measured and the calculated amplitudes of the Pressure Head loss by the empirical equation is 10.77%. Since the relative errors are small, it is an indication that the amplitudes of the Pressure Head loss calculated by the empirical equation are accurate. For the empirical equation developed in this study, the sensitivity of the model parameters has been analyzed. The results show that the amplitude of velocity, the internal pipe diameter, and the length of pipe are classified as highly sensitive. The average velocity, the period of oscillating water flow, and the modulus of elasticity of the pipe material are classified as sensitive. The thickness of the pipe wall is classified as medium sensitive. Compared with the calculation models of the existing researches, the empirical equation reduces the number of parameters required to be calculated, by which many complicated calculations are avoided, which greatly improves the computing efficiency. This is conducive to the efficient operation and management of oscillating water flow in irrigation pipe networks and also provides help for the optimal design of irrigation pipe networks.
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The Development of a Calculation Model for the Instantaneous Pressure Head of Oscillating Water Flow in a Pipeline
Water, 2019Co-Authors: Kai Zhang, Bo Song, Delan ZhuAbstract: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.
G.h. De Rooij - One of the best experts on this subject based on the ideXlab platform.
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The Pressure Head regime in the induction zone during unstable nonponding infiltration: theory and experiments
Vadose Zone Journal, 2005Co-Authors: Hiroyuki Cho, G.h. De Rooij, Mitsuhiro InoueAbstract:Fingered flow rapidly moves water and pollutants from the root zone to the groundwater through a limited fraction of the unsaturated zone, limiting the possibilities for decay and adsorption. The onset of wetting front instability and the characteristics of the flow pattern under nonponding infiltration have received limited attention. We aim to theoretically and experimentally advance our understanding of pre-fingered flow, and contrast fingered flow under ponding and nonponding conditions. We developed a Green-Ampt based expression for the Pressure Head in a developing induction zone (from which fingers protrude) for the time before fingers developed. A uniform, nonponding water flux was applied to the surface of two-dimensional glass bead porous media with a dry region above a capillary fringe. Microtensiometers recorded Pressure Heads in the induction zone. The Pressure Head data confirmed both the theoretical early-time pre-finger model, and a model developed earlier for late-time lateral flow toward fully developed fingers. The physically more realistic constant flux boundary condition of our experiments gave larger finger spacings and travel times, compared to the frequently used set-up with ponding infiltration into a fine-over-coarse porous medium
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Pressure Head distribution during unstable flow in relation to the formation and dissipation of fingers
Hydrology and Earth System Sciences, 2002Co-Authors: G.h. De RooijAbstract:Abstract. Wetting front instability creates a shallow induction zone from which fingers emerge that rapidly transport water and solutes downwards. How the induction zone affects finger location and spacing is unknown. In the moist subsoil, fingers may well dissipate because the finger tips no longer have to overcome the water entry value. Both flow regions were investigated in a two-dimensional chamber with a fine-over-coarse glass bead porous medium. A capillary fringe was created by upward wetting through capillary rise. Upon ponding with dye-coloured water, fingers emerged, propagated downward and diverged when reaching the capillary fringe. Microtensiometers were installed in the induction zone, the fingers, and in the capillary fringe. In the induction zone, a lateral sinusoidal Pressure Head developed within minutes. Only in one of two experiments could the observed Pressure Head pattern be satisfactorily reproduced by a steady-state model assuming uniform induction zone properties and uniform infiltration. Later, fingers emerged below the Pressure Head minima. The induction zone did not affect finger properties. The Pressure Head in the induction zone was determined by the depth of the finger tips. The water requirement of the fingers dictated the lateral Pressure Head gradients. The Pressure Heads in the capillary fringe supported the hypothesis that the flow stabilised and dissipated there. Keywords: fingered flow, wetting front instability, unsaturated flow, microtensiometers, induction zone, capillary fringe
Pierre Benoit - One of the best experts on this subject based on the ideXlab platform.
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Water Pressure Head and temperature impact on isoxaflutole degradation in crop residues and loamy surface soil under conventional and conservation tillage management
Chemosphere, 2012Co-Authors: Lionel Alletto, Valérie Bergheaud, Yves Coquet, Pierre BenoitAbstract:Laboratory incubations were performed in order to evaluate the dissipation of the proherbicide isoxaflutole in seedbed layer soil samples from conventional and conservation tillage systems and in maize and oat residues left at the soil surface under conservation tillage. The effects of temperature and water Pressure Head on radiolabelled isoxaflutole degradation were studied for each sample for 21 d. Mineralisation of isoxaflutole was low for all samples and ranged from 0.0% to 0.9% of applied 14C in soil samples and from 0.0% to 2.4% of applied 14C in residue samples. In soil samples, degradation half-life of isoxaflutole ranged from 9 to 26 h, with significantly higher values under conservation tillage. In residue samples, degradation half-life ranged from 3 to 31 h, with significantly higher values in maize residues, despite a higher mineralisation and bound residue formation than in oat residues. Whatever the sample, most of the applied 14C remained extractable during the experiment and, after 21 d, less than 15% of applied 14C were unextractable. This extractable fraction was composed of diketonitrile, benzoic acid derivative and several unidentified metabolites, with one of them accounting for more than 17% of applied 14C. This study showed that tillage system design, including crop residues management, could help reducing the environmental impacts of isoxaflutole.
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Temperature and water Pressure Head effects on the degradation of the diketonitrile metabolite of isoxaflutole in a loamy soil under two tillage systems.
Environmental pollution (Barking Essex : 1987), 2008Co-Authors: Lionel Alletto, Pierre Benoit, Valérie Bergheaud, Yves CoquetAbstract:Abstract Laboratory studies were conducted to evaluate the effects of temperature and water Pressure Head on the degradation of the diketonitrile metabolite (DKN) of isoxaflutole during 84 d in samples collected in a loamy soil under conventional (CT) and conservation (MT) tillage systems. Soil temperature was the major factor controlling DKN degradation in the two tillage systems. The shortest half-lives ( T 1/2 ) were measured in the seedbed samples under MT at 25 °C and −33 cm water Pressure Head. We found that mouldboard ploughing under CT was responsible for the spatial variability of herbicide degradation properties, whereas under MT herbicide degradation was associated to the vertical distribution of organic matter.
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Temperature and water Pressure Head effects on the degradation of the diketonitrile metabolite of isoxaflutole in a loamy soil under two tillage systems
Environmental Pollution, 2008Co-Authors: Lionel Alletto, Pierre Benoit, Valérie Bergheaud, Yves CoquetAbstract:Laboratory studies were conducted to evaluate the effects of temperature and water Pressure Head on the degradation of the diketonitrile metabolite (DKN) of isoxaflutole during 84 d in samples collected in a loamy soil under conventional (CT) and conservation (MT) tillage systems. Soil temperature was the major factor controlling DKN degradation in the two tillage systems. The shortest half-lives (T1/2) were measured in the seedbed samples under MT at 25 °C and -33 cm water Pressure Head. We found that mouldboard ploughing under CT was responsible for the spatial variability of herbicide degradation properties, whereas under MT herbicide degradation was associated to the vertical distribution of organic matter. Tillage practices influence the spatial variability of diketonitrile degradation in soil and its sensitivity to pedoclimatic conditions.
Yves Coquet - One of the best experts on this subject based on the ideXlab platform.
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Water Pressure Head and temperature impact on isoxaflutole degradation in crop residues and loamy surface soil under conventional and conservation tillage management
Chemosphere, 2012Co-Authors: Lionel Alletto, Valérie Bergheaud, Yves Coquet, Pierre BenoitAbstract:Laboratory incubations were performed in order to evaluate the dissipation of the proherbicide isoxaflutole in seedbed layer soil samples from conventional and conservation tillage systems and in maize and oat residues left at the soil surface under conservation tillage. The effects of temperature and water Pressure Head on radiolabelled isoxaflutole degradation were studied for each sample for 21 d. Mineralisation of isoxaflutole was low for all samples and ranged from 0.0% to 0.9% of applied 14C in soil samples and from 0.0% to 2.4% of applied 14C in residue samples. In soil samples, degradation half-life of isoxaflutole ranged from 9 to 26 h, with significantly higher values under conservation tillage. In residue samples, degradation half-life ranged from 3 to 31 h, with significantly higher values in maize residues, despite a higher mineralisation and bound residue formation than in oat residues. Whatever the sample, most of the applied 14C remained extractable during the experiment and, after 21 d, less than 15% of applied 14C were unextractable. This extractable fraction was composed of diketonitrile, benzoic acid derivative and several unidentified metabolites, with one of them accounting for more than 17% of applied 14C. This study showed that tillage system design, including crop residues management, could help reducing the environmental impacts of isoxaflutole.
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Temperature and water Pressure Head effects on the degradation of the diketonitrile metabolite of isoxaflutole in a loamy soil under two tillage systems.
Environmental pollution (Barking Essex : 1987), 2008Co-Authors: Lionel Alletto, Pierre Benoit, Valérie Bergheaud, Yves CoquetAbstract:Abstract Laboratory studies were conducted to evaluate the effects of temperature and water Pressure Head on the degradation of the diketonitrile metabolite (DKN) of isoxaflutole during 84 d in samples collected in a loamy soil under conventional (CT) and conservation (MT) tillage systems. Soil temperature was the major factor controlling DKN degradation in the two tillage systems. The shortest half-lives ( T 1/2 ) were measured in the seedbed samples under MT at 25 °C and −33 cm water Pressure Head. We found that mouldboard ploughing under CT was responsible for the spatial variability of herbicide degradation properties, whereas under MT herbicide degradation was associated to the vertical distribution of organic matter.
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Temperature and water Pressure Head effects on the degradation of the diketonitrile metabolite of isoxaflutole in a loamy soil under two tillage systems
Environmental Pollution, 2008Co-Authors: Lionel Alletto, Pierre Benoit, Valérie Bergheaud, Yves CoquetAbstract:Laboratory studies were conducted to evaluate the effects of temperature and water Pressure Head on the degradation of the diketonitrile metabolite (DKN) of isoxaflutole during 84 d in samples collected in a loamy soil under conventional (CT) and conservation (MT) tillage systems. Soil temperature was the major factor controlling DKN degradation in the two tillage systems. The shortest half-lives (T1/2) were measured in the seedbed samples under MT at 25 °C and -33 cm water Pressure Head. We found that mouldboard ploughing under CT was responsible for the spatial variability of herbicide degradation properties, whereas under MT herbicide degradation was associated to the vertical distribution of organic matter. Tillage practices influence the spatial variability of diketonitrile degradation in soil and its sensitivity to pedoclimatic conditions.
Quirijn De Jong Van Lier - One of the best experts on this subject based on the ideXlab platform.
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Canopy temperature versus soil water Pressure Head for the prediction of crop water stress
Agricultural Water Management, 2013Co-Authors: Angelica Durigon, Quirijn De Jong Van LierAbstract:Abstract Plant water stress is linked to both above- and below-surface parameters; with above-surface parameters being generally easier to measure. Models utilizing above-surface parameters, such as canopy temperature to identify plant water stress, frequently employ the crop water stress index (CWSI). Alternatively, the regular usage of the transpiration reduction function (FRF), as proposed by Feddes in the 1970s, requires more difficult to measure below-surface parameters such as soil water Pressure Head. In order to assess the agreement between these models, we experimentally compared plant water stress predicted by the CWSI and FRF using Common Bean grown in Brazil under full and deficit irrigation; the sensitivity of the models to the key parameters, water stressed baseline and limiting soil water Pressure Head, was also evaluated. The simple equation 1 − CWSI = Tr provided a good fit when relating CWSI to the relative transpiration Tr as predicted by the Feddes model. We show that above ground measurements that are combined within the CWSI are just as effective at predicting plant water stress as soil-based factors like soil water Pressure Head. The models show high sensitivity to variations in key parameters, implying significant differences will result in the identification of the onset of plant water stress; with sensitivity highest for the CWSI under dry conditions.
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Pressure Heads and Simulated Water Uptake Patterns for a Severely Stressed Bean Crop
Vadose Zone Journal, 2012Co-Authors: Angelica Durigon, Quirijn De Jong Van Lier, Marcos Alex Dos Santos, Klaas MetselaarAbstract:In modeling, actual crop transpiration as a function of soil hydraulic conditions is usually estimated from a water content or Pressure Head dependent reduction function. We compared the performance of the empirical Pressure Head based reduction function of Feddes (FRF) and a more physically based reduction function using matric flux potential as the main parameter (DRF), both available in the SWAP ecohydrological model. Model performance was evaluated by comparison of SWAP predictions and observed water contents and Pressure Head values in a field experiment with a common bean (Phaseolus vulgaris L.) crop. For >50 d, no rain occurred and the soil reached very dry conditions with Pressure Heads in the range -100 to -150 m. The SWAP-DRF-predicted Pressure Head and water content values were less sensitive to root length density distribution than those predicted by SWAP-FRF. Varying wilting Pressure Head did not improve predictive performance. Root water uptake distribution with time and depth simulated by SWAP showed very different patterns depending on the reduction function used. Root water uptake estimated by SWAP-FRF showed smooth transitions with time and between layers, whereas SWAP-DRF, highly sensitive to hydraulic conditions, generally predicted uptake to be concentrated at a few depths. The order of magnitude of the Pressure Head difference between root xylem and root surface based on SWAP-DRF-predicted uptake rates, root length density, and reported values of root conductance was the same as the order of magnitude of the limiting root water Pressure Head, implying the necessity to include root hydraulic resistance in the DRF.