scholarly journals Analytical Solutions of Vertical Airflow in an Unconfined Aquifer with Rising or Falling Water Table

Water ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 625
Author(s):  
Ran An ◽  
Pei Dong ◽  
Jun-Zhi Wang ◽  
Yifan Zhang ◽  
Xianfang Song ◽  
...  
Keyword(s):  
Water Flow ◽  
Water Table ◽  
Vadose Zone ◽  
Analytical Solutions ◽  
Air Flow ◽  
Thick Layer ◽  
Unconfined Aquifer ◽  
Positive Pressure ◽  
Low Permeability ◽  
Cap Layer

The rise and fall of the groundwater level can drive air flow in the vadose zone. In turn, the air flow can interact with the water flow. When the unconfined aquifer is covered by a low-permeability media, the coupling of the water flow and the air flow is more obvious. In this study, a conceptual model is established for coupling of air flow and water flow in the vadose zone in response to rapid fluctuations of the water table. Water injection and drainage experiments are conducted in a double-layered sand column with a thick layer (80.5 cm) of coarse sand and a thin layer of fine sand as a low-permeability cap. Different cap thickness (2 cm, 5 cm, 7.5 cm) and different thickness of the vadose zone (30 cm, 40 cm) are set for the experiments. Negative pressure (NP)/positive pressure (PP) of the air in the vadose zone is observed in the drainage/injection experiments, with higher pressure in experiments of thicker cap layer. In each experiment, NP or PP increases rapidly to reach a maximum in the early stage, and gradually becomes zero in the late stage. Analytical solutions on three subdivided stages indicate the permeability and thickness of the cap layer, as well as permeability and porosity of the media in the vadose zone are the key controlling factors on the process of coupling of air flow and water flow. The solutions also reveal the formation mechanism of air pressure in the vadose zone with a low-permeability cap. This study has both theoretical significance and engineering applications.

Écoulement saturé et non saturé de l’eau souterraine vers des drains en aquifère à nappe libre

2008 ◽  
Vol 45 (9) ◽  
pp. 1210-1223 ◽  
Author(s):  
Robert P. Chapuis ◽  
Adrienne Dénes
Keyword(s):  
Hydraulic Conductivity ◽  
Vadose Zone ◽  
Analytical Solutions ◽  
Unconfined Aquifer ◽  
Soil Characteristic ◽  
Flow Rates ◽  
Simplifying Assumptions ◽  
Construction Schedule ◽  
Engineering Projects ◽  
Unsaturated Seepage

The drainage of sports fields, highways, farm lands, and covers for wastes corresponds to the drainage of a shallow unconfined aquifer resting on a horizontal or sloping impervious substratum. The seepage, partly saturated and partly unsaturated, is thus described by nonlinear equations that are not easy to solve. A few analytical solutions exist; they were obtained after several simplifying assumptions. Are they realistic? In this paper, comparisons are made between predictions from analytical solutions and those from numerical resolutions (for saturated and unsaturated seepage) under steady and transient states. The analytical solutions predict a water table and flow rates that differ significantly from those of the numerical resolutions, and are sometimes unrealistic. Corrections to the analytical solutions have already been proposed to account for the vadose zone. Despite such corrections, the published solutions to drainage problems may be inaccurate. In engineering projects where the duration of drainage may be critical for the construction schedule, it is recommended to avoid the analytical equations and to use numerical codes that solve the complete differential equations by taking into account the complete soil characteristic curves for hydraulic conductivity and capillary retention, which can be obtained using permeability tests and capillary-retention tests.

scholarly journals Analytical solutions to the stream-aquifer interaction problem: a critical review

2013 ◽  
Vol 12 (2) ◽  
pp. 126-139
Keyword(s):  
Analytical Solution ◽  
Mathematical Models ◽  
Ground Water ◽  
Water Flow ◽  
Water Table ◽  
Analytical Solutions ◽  
Stream Flow ◽  
Boussinesq Equation ◽  
Ground Water Flow ◽  
Flow Equations

The aim of the present paper is to give a systematic and critical presentation of important existing analytical solutions for transient stream-aquifer interaction, which can be used to give answers to simple interaction problems or to verify mathematical models. Stream-aquifer interaction is the most common subject of papers discussing surface water-ground water interaction and a review of analytical solutions to the problem is lacking from the literature. The analytical solutions presented in the paper are firstly distinguished based on whether only the ground water flow equations or both the ground water and stream flow equations are solved for their derivation and secondly based on the type of aquifer (confined or unconfined) interacting with the stream and on the type of equations solved. The literature review showed that there is only a small number of publications, where the authors consider both the ground water and the stream flow equations for the development of the analytical solutions. The majority of the available analytical solutions of stream-aquifer interaction are derived by solving only the ground water flow equations, taking into account the stream water level as a boundary condition. For each analytical solution presented in the paper, its accuracy, its ease of application to simple interaction problems and its suitability for the verification of mathematical models are discussed in detail. Specifically for the case of predicting the water table level in unconfined aquifers interacting with streams, an analytical solution of the non-linear Boussinesq equation is compared to two analytical solutions of different linearized forms of the Boussinesq equation, in order to quantify the error in estimating the water table level when using a linear solution. Among the very few analytical solutions found in the literature, where the authors consider both the stream flow and ground water flow equations for their development, the most comprehensive one is chosen to give an application example, which can be used as a benchmark case for the verification of integrated stream-aquifer mathematical models.

scholarly journals Seismoelectric imaging of the vadose zone of a sand aquifer

Geophysics ◽  
2007 ◽  
Vol 72 (6) ◽  
pp. A81-A85 ◽  
Author(s):  
J. Christian Dupuis ◽  
Karl E. Butler ◽  
Anton W. Kepic
Keyword(s):  
Water Table ◽  
Vadose Zone ◽  
Ground Penetrating Radar ◽  
Seismic Source ◽  
Unconfined Aquifer ◽  
Recording System ◽  
Sedimentary Environments ◽  
Sand Aquifer ◽  
Weight Drop ◽  
Ground Penetrating

We have acquired a [Formula: see text] seismoelectric section over an unconfined aquifer to demonstrate the effectiveness of interfacial signals at imaging interfaces in shallow sedimentary environments. The seismoelectric data were acquired by using a [Formula: see text] accelerated weight-drop source and a 24-channel seismoelectric recording system composed of grounded dipoles, preamplifiers, and seismographs. In the shot records, interfacial signals were remarkably clear; they arrived simultaneously at offsets as far as [Formula: see text] from the seismic source. The most prominent signal was generated at the water table at a depth of approximately [Formula: see text] and had peak amplitudes on the order of [Formula: see text]. A weaker response was generated at a shallower interface that is interpreted to be a water-retentive layer. The validity of these two laterally continuous events, and of other discontinuous events indicative of vadose-zone heterogeneity, is corroborated by the presence of reflections exhibiting similar characteristics in a ground-penetrating radar profile acquired along the same line.

scholarly journals Geometrical Optimization of a Venturi-Type Microbubble Generator Using CFD Simulation and Experimental Measurements

Designs ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 4
Author(s):  
Dillon Alexander Wilson ◽  
Kul Pun ◽  
Poo Balan Ganesan ◽  
Faik Hamad
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Air Flow ◽  
Bubble Diameter ◽  
Diameter Ratio ◽  
Experimental Measurements ◽  
Cfd Model ◽  
Flow Rates ◽  
Throat Diameter

Microbubble generators are of considerable importance to a range of scientific fields from use in aquaculture and engineering to medical applications. This is due to the fact the amount of sea life in the water is proportional to the amount of oxygen in it. In this paper, experimental measurements and computational Fluid Dynamics (CFD) simulation are performed for three water flow rates and three with three different air flow rates. The experimental data presented in the paper are used to validate the CFD model. Then, the CFD model is used to study the effect of diverging angle and throat length/throat diameter ratio on the size of the microbubble produced by the Venturi-type microbubble generator. The experimental results showed that increasing water flow rate and reducing the air flow rate produces smaller microbubbles. The prediction from the CFD results indicated that throat length/throat diameter ratio and diffuser divergent angle have a small effect on bubble diameter distribution and average bubble diameter for the range of the throat water velocities used in this study.

LINKFLOW, A WATER FLOW COMPUTER MODEL FOR WATER TABLE MANAGEMENT: PART 3. MODEL APPLICATION

1997 ◽  
Vol 40 (6) ◽  
pp. 1543-1547 ◽  
Author(s):  
P. L. Havard ◽  
S. O. Prasher ◽  
R. B. Bonnell ◽  
A. Madani
Keyword(s):  
Water Flow ◽  
Water Table ◽  
Computer Model ◽  
Model Application ◽  
Water Table Management

Quasi 3D modeling of water flow in vadose zone and groundwater

2012 ◽  
Vol 450-451 ◽  
pp. 140-149 ◽  
Author(s):  
M. Kuznetsov ◽  
A. Yakirevich ◽  
Y.A. Pachepsky ◽  
S. Sorek ◽  
N. Weisbrod
Keyword(s):  
Water Flow ◽  
Vadose Zone ◽  
3D Modeling

scholarly journals Experimental Investigation on Improvement of Wet Cooling Tower Efficiency with Diverse Packing Compaction Using ANN-PSO Algorithm

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 167
Author(s):  
Hasan Alimoradi ◽  
Madjid Soltani ◽  
Pooriya Shahali ◽  
Farshad Moradi Kashkooli ◽  
Razieh Larizadeh ◽  
...  
Keyword(s):  
Neural Network ◽  
Water Temperature ◽  
Water Flow ◽  
Flow Rate ◽  
Cooling Tower ◽  
Air Flow ◽  
Water Flow Rate ◽  
Pso Algorithm ◽  
Outlet Temperature ◽  
Air Flow Rate

In this study, a numerical and empirical scheme for increasing cooling tower performance is developed by combining the particle swarm optimization (PSO) algorithm with a neural network and considering the packing’s compaction as an effective factor for higher accuracies. An experimental setup is used to analyze the effects of packing compaction on the performance. The neural network is optimized by the PSO algorithm in order to predict the precise temperature difference, efficiency, and outlet temperature, which are functions of air flow rate, water flow rate, inlet water temperature, inlet air temperature, inlet air relative humidity, and packing compaction. The effects of water flow rate, air flow rate, inlet water temperature, and packing compaction on the performance are examined. A new empirical model for the cooling tower performance and efficiency is also developed. Finally, the optimized performance conditions of the cooling tower are obtained by the presented correlations. The results reveal that cooling tower efficiency is increased by increasing the air flow rate, water flow rate, and packing compaction.

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