Fertilization equipment is a crucial component of irrigation systems, and its performance directly impacts irrigation quality. To address the issues of low suction flow and excessive head loss in existing Venturi fertilizer injectors, the team employed numerical simulation techniques. Through single-factor experiments, we analyzed the effect of the suction pipe angle of the dual-throat Venturi fertilizer injector on its suction performance, ultimately determining the optimal structural parameter combination for the injector. The study utilized software such as Tecplot and CFD to analyze the influence of various structural parameters on the internal pressure, turbulent kinetic energy, and vortex distribution within the dual-throat Venturi fertilizer injector, examining the patterns of internal flow field variations. The angle of the suction pipe significantly affects suction performance; adjusting the suction pipe to the optimal angle helps reduce turbulent kinetic energy at the throat, increase negative pressure, and decrease both the area and intensity of vortices. This, in turn, minimizes the intensity of multidirectional velocity collisions and the head loss caused by vortices, leading to a substantial enhancement in both suction and hydraulic performance.
Could advances in geoinformatics, irrigation management and climate adaptive agronomic practices ensure the sustainability of water supply in agriculture? This book comprises 33 chapters that contribute to a broad discussion and demonstration of state-of-the-art multifunctional role of water resources in agriculture. The aim of the book to provide insights into novel modelling (monitoring, analyzing/visualizing and prediction) approaches, irrigation management and agronomic practices to investigate the adaptability of water supply and crop production systems to changing environment. The book presents characteristic examples of new technologies and decision support systems (e.g., artificial intelligence/optimization modelling approaches, Big Geo data) in water efficiency at different levels, including: water supply hydraulic infrastructure systems, water retention measures, less exposed to evaporation and better adapted to infiltration, solutions to reduce water demand and developing techniques for reusing water.In Focus–a book series that showcases the latest accomplishments in water research. Each book focuses on a specialist area with papers from top experts in the field. It aims to be a vehicle for in-depth understanding and inspire further conversations in the sector.
In China, agricultural irrigation water often contains a lot of suspended sediment which may cause the nozzle wear. In this study, a new numerical simulation combing the Discrete Phase Model and a remeshing algorithm was conducted. The geometric boundary deformation caused by the erosion wear, was considered. The weight loss of the nozzle, the node displacement and the flow field were investigated and discussed. The timestep sensitivity analysis showed that the timestep is very critical in the erosion modeling due to the randomness and the discreteness of the erosion behavior. Based on the simulation results, the major deformation of the boundary wall due to the erosion was found at the corners between outlet portion and contraction portion. Based on this remeshing algorithm, the simulated erosion weight loss of the nozzle is 4.62% less compared with the case without boundary deformation. The boundary deformation changes the pressure and velocity distribution, and eventually changes the sediment distribution inside the nozzle. The average turbulence kinetic energy at the outlet orifice is found to decrease with the erosion time, which is believed to change the nozzle’s spray performance eventually.
Abstract Droplet shear stress is the main cause of soil erosion under sprinkler irrigation, and the effect of droplet impact angle on the shear stress distribution cannot be ignored. In this study, a ball-driven sprinkler was selected to investigate the radial distributions of droplet impact angles under three operating pressures (0.25, 0.30, and 0.35 MPa) and two nozzle diameters (1.9 and 2.2 mm), which are commonly used in agricultural irrigation. The effect of droplet impact angles on the distances from the sprinkler, droplet impact velocities, and shear stresses were analyzed by a 2DVD instrument. Irrespective of the nozzle diameter or operating pressure, the droplet velocities and impact angles near the sprinkler were distributed at 1.0–5.5 m s−1 and 70–90°, respectively, and the droplet shear stress increased with the distance from the sprinkler. Suitable operating pressure and distance from the sprinkler significantly reduced the droplet shear stress. Although the nozzle diameter had a certain effect on the maximum shear stress, the overall effect was insignificant. We developed the models for the radial distribution of droplet shear stresses, which were in good agreement with the measurement. This study proposes a new method for accurately predicating the soil erosion under sprinkler irrigation.
To investigate the effect of information transmission, Lévy jumps and contact heterogeneity of individuals on the asymptotic behavior of epidemic, a stochastic SIQR epidemic model with non-monotone incidence rate and Lévy jumps on scale-free networks is constructed. At first, the global dynamics of the deterministic model is studied by constructing appropriate Lyapunov functions. Then the stochastic model is made in accordance with the ecological significance, the existence and uniqueness of the global positive solution of the stochastic SIQR model is manifested. Next, by constructing suitable stochastic Lyapunov functions and applying Itô formula with jump, the asymptotic behavior of solutions of stochastic model around equilibrium of the corresponding deterministic model is checked. At last, the correctness of the analytical results is verified by numerical simulations.
Hydraulic structures, such as bridges, dikes, engineered logs, rock weirs and vanes, are common in engineering practice. Their existence presents a disturbance to the flow field in rivers and coastal regions. As a result, the sediment transport around these structures is disturbed and consequently results in scour and erosion. This work aims to simulate the sediment transport and bed morphological changes induced by complex structures in real world. Previously we have developed Arbitrary-Lagrangian-Eulerian (ALE) method to track the deformed bed, which is useful for scour around simple geometries. It is difficult and sometime fails to model scour around complex structures. We present a new model which uses an immersed boundary method (IBM) to dynamically track the geometrical deformation of the bed. This method eliminates the need of mesh deformation or remeshing in an ALE approach. The model is developed in the open source computational fluid dynamics platform OpenFOAM. Local scour is ubiquitous in natural and built environments where flowing water moves sediment. In natural rivers, it is part of the process which creates the landscape. In engineered systems, it is a phenomenon which could endanger the stability of structures. To understand and predict the local scour process is thus of great importance. Computational models have been previously proposed and developed to predict the flow field and scour around hydraulic structures. However, there are still great challenges to accurately predict the evolution of sediment bed around objects with complex shape. Part of the reason is that it is hard to track the surface dynamically during simulation. Previously, mesh deformation method, i.e., the Arbitrary-Lagrangian-Eulerian (ALE) approach, has been used where a body-fitted mesh deforms as the bottom evolves its shape (Liu and Garcia, 2008; Roulund et al, 2005). The ALE method can only be used for simple geometries. In this work, we present a new model which utilizes the immersed boundary method for the sediment bed. In this method, the background mesh does not change. Instead, the evolving bed is modeled as an immersed boundary and its effect to the flow field is implicitly imposed. The evolution of the immersed bed is governed by the conservation of sediment. Overall, the new model has two parts. One is the hydro-dynamic part and the other is the morphological part. This paper will first briefly introduce the two parts of the scour model and then show some preliminary results.
High-density attachment of Limnoperna fortunei (LF) would lead to the increase of flow resistance, which has posed big challenges to the normal operation of water conveyance projects. It is very necessary to quantify the flow resistance caused by the attachment of LF. In this study, a 3D geometric model of LF was generated based on real images. Attachment models of LF were generated with different densities and mussel size distributions, whose geometric characteristics were evaluated by some fundamental physical quantities, including attachment thickness, bed coverage, surface vertical roughness, and roughness concentration. Furtherly, a 3D numerical model with specific boundary conditions was established in OpenFOAM to simulate the flow over the LF attachment. Body-fitted mesh was generated using snappyHexMesh based on the LF attachment model. The results show that in high-density scenarios, a big wake zone formed inside LF attachment by the combined effects of each individual LF. Turbulence kinetic energy distribution indicated that LF attachment would cause viscous dissipation thus leading to more energy loss. The flow structure inside LF attachment was controlled by the size and spacing between each individual LF. Manning’s n values were calculated based on the CFD results at different densities. The results show that the flow resistance of LF attachment also followed the classic flow regimes, where in the skimming flow regime, the mussel size distribution played a non-negligible role. Higher flow speed resulted in larger flow resistance, and n could increase more than 90% compared to the scenario without LF attachment.
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