scholarly journals On Coupled Unsaturated-Saturated Flow Process Induced by Vertical, Horizontal and Slant Wells in Unconfined Aquifers

2016 ◽  
Author(s):  
Xiuyu Liang ◽  
Hongbin Zhan ◽  
You-Kuan Zhang ◽  
Jin Liu
Keyword(s):  
Unsaturated Zone ◽  
Horizontal Well ◽  
Unsaturated Flow ◽  
Three Dimensional ◽  
Early Time ◽  
Saturated Flow ◽  
Flow Process ◽  
Pumping Tests ◽  
Screen Length ◽  
Unconfined Aquifers

Abstract. Conventional models of pumping tests in unconfined aquifers often neglect the unsaturated flow process. This study concerns coupled unsaturated-saturated flow process induced by vertical, horizontal, and slant wells positioned in an unconfined aquifer. A mathematical model is established with special consideration of the coupled unsaturated-saturated flow process and well orientation. Groundwater flow in the saturated zone is described by a three-dimensional governing equation, and a linearized three-dimensional Richards' equation in the unsaturated zone. A solution in Laplace domain is derived by the Laplace-finite Fourier transform and the method of separation of variables. It is found that the unsaturated zone has significant effects on the drawdown of pumping test with any angle of inclination of the pumping well, and this impact is more significant for the case of a horizontal well. The effects of unsaturated zone on the drawdown are independent of the length of the horizontal well screen. For the early time of pumping, the water volume drained from the unsaturated zone (W) increases with time, and gradually approaches an asymptotic value with time progress. The vertical well leads to the largest W value during the early time, and the effects of the well orientation become insignificant at the later time. The screen length of the horizontal well does not affect W for the whole pumping period. The proposed solutions are useful for parameter identification of pumping tests with a general well orientation (vertical, horizontal, and slant) in unconfined aquifers affected from above by the unsaturated flow process.

scholarly journals On the coupled unsaturated–saturated flow process induced by vertical, horizontal, and slant wells in unconfined aquifers

2017 ◽  
Vol 21 (2) ◽  
pp. 1251-1262 ◽  
Author(s):  
Xiuyu Liang ◽  
Hongbin Zhan ◽  
You-Kuan Zhang ◽  
Jin Liu
Keyword(s):  
Unsaturated Zone ◽  
Horizontal Well ◽  
Unsaturated Flow ◽  
Three Dimensional ◽  
Water Volume ◽  
Saturated Flow ◽  
Flow Process ◽  
Pumping Tests ◽  
Screen Length ◽  
Unconfined Aquifers

Abstract. Conventional models of pumping tests in unconfined aquifers often neglect the unsaturated flow process. This study concerns the coupled unsaturated–saturated flow process induced by vertical, horizontal, and slant wells positioned in an unconfined aquifer. A mathematical model is established with special consideration of the coupled unsaturated–saturated flow process and the well orientation. Groundwater flow in the saturated zone is described by a three-dimensional governing equation and a linearized three-dimensional Richards' equation in the unsaturated zone. A solution in the Laplace domain is derived by the Laplace–finite-Fourier-transform and the method of separation of variables, and the semi-analytical solutions are obtained using a numerical inverse Laplace method. The solution is verified by a finite-element numerical model. It is found that the effects of the unsaturated zone on the drawdown of a pumping test exist at any angle of inclination of the pumping well, and this impact is more significant in the case of a horizontal well. The effects of the unsaturated zone on the drawdown are independent of the length of the horizontal well screen. The vertical well leads to the largest water volume drained from the unsaturated zone (W) during the early pumping time, and the effects of the well orientation on W values become insignificant at the later time. The screen length of the horizontal well does not affect W for the whole pumping period. The proposed solutions are useful for the parameter identification of pumping tests with a general well orientation (vertical, horizontal, and slant) in unconfined aquifers affected from above by the unsaturated flow process.

scholarly journals Coupling saturated and unsaturated flow: comparing the iterative and the non-iterative approach

2021 ◽  
Author(s):  
Natascha Brandhorst ◽  
Daniel Erdal ◽  
Insa Neuweiler
Keyword(s):  
Unsaturated Zone ◽  
Unsaturated Flow ◽  
Three Dimensional ◽  
Lower Boundary ◽  
3D Models ◽  
Specific Yield ◽  
Iterative Approach ◽  
Groundwater Model ◽  
Iterative Coupling ◽  
Fully Integrated

Abstract. Fully integrated three dimensional (3D) physically based hydrologic models usually require many computational resources. For many applications, simplified models can be a cost effective alternative. 3D models of subsurface flow are often simplified by coupling a 2D groundwater model with multiple 1D models for the unsaturated zone. The crucial part of such models is the coupling between the two model compartments. In this work we compare two approaches for the coupling. One is iterative and the 1D unsaturated zone models go down to the impervious bottom of the aquifer and the other one is non-iterative and uses a moving lower boundary for the unsaturated zone. In this context we also propose a new way of treating the specific yield, which plays a crucial role in linking the unsaturated and the groundwater model. Both models are applied to three test cases with increasing complexity and analyzed in terms of accuracy and speed compared to fully integrated model runs. The non-iterative approach is faster while the iterative approach is more accurate and robust. Besides, for the iterative coupling method a calibration of the specific yield is not needed.

scholarly journals Geostatistic Interpolation of Soil Moisture

1997 ◽  
Vol 28 (4-5) ◽  
pp. 307-328 ◽  
Author(s):  
Nils-Otto Kitterød ◽  
E. Langsholt ◽  
W. K. Wong ◽  
L. Gottschalk
Keyword(s):  
Soil Moisture ◽  
Unsaturated Zone ◽  
Preferential Flow ◽  
Unsaturated Flow ◽  
Three Dimensional ◽  
Indicator Kriging ◽  
Flow Paths ◽  
Flow Models ◽  
Semivariogram Analysis ◽  
Preferential Flow Paths

The spatial distribution of soil moisture defines preferential flow paths in the unsaturated zone. Hence, three dimensional (3D) estimates of soil moisture are of great importance to understand transport of contaminants as well as remediation processes in the unsaturated zone. In this study 3D estimates conditioned on spatially frequent observations of soil moisture, have been obtained by kriging. The observations were divided into subdomains consistent with the local stratigraphy and directional semivariogram analysis was applied. It was found difficult to clearly identify a 3D semivariogram function in this case, but from a georadar survey two semivariogram functions were derived, describing two different sedimentological units. By conditioning the estimates of soil moisture on the sedimentological architecture computed by indicator kriging, more accurate estimates were achieved. These improvements were quantified by a ‘jackknife’ cross validation procedure. Besides the practical aspects of finding the most important flow paths estimates of soil moisture are valuable when validating unsaturated flow models.

scholarly journals Analysis of three-dimensional unsaturated-saturated flow induced by localized recharge in unconfined aquifers

2017 ◽  
Author(s):  
Chia-Hao Chang ◽  
Ching-Sheng Huang ◽  
Hund-Der Yeh
Keyword(s):  
Soil Properties ◽  
Unsaturated Soil ◽  
Unsaturated Flow ◽  
Three Dimensional ◽  
Hydraulic Head ◽  
Richards Equation ◽  
Coupled Flow ◽  
Saturated Flow ◽  
Flow Equations ◽  
Present Solution

Abstract. In the process of groundwater recharge, surface water usually enters an aquifer by passing an overlying unsaturated zone. Up to now, little attention has been given to the effect of unsaturated flow on the hydraulic head within the aquifer due to recharge. This paper develops a mathematical model to depict three-dimensional transient unsaturated-saturated flow in an unconfined aquifer with localized recharge on the ground surface. The model contains Richards’ equation for unsaturated flow, a flow equation for saturated formation, and the Gardner constitutive model describing the behavior of unsaturated soil properties. Both flow equations are coupled through the continuity conditions of the head and flux at the water table. The semi-analytical solution to the coupled flow model is derived by the methods of Laplace transform and Fourier cosine transform. A sensitivity analysis is performed to explore the head response to the change in each of the aquifer parameters. A quantitative tool is presented to assess the recharge efficiency signifying the percentage of the water from the recharge to the aquifer. We found that the effect of unsaturated flow on the saturated hydraulic head is negligible if two criteria associated with the unsaturated soil properties and initial aquifer thickness are satisfied. The head distributions predicted from the present solution match well with those from finite element simulations. The predictions of the present solution also agree well with the observed data from a field experiment at an artificial recharge pond in Fresno County, California.

scholarly journals Analysis of three-dimensional unsaturated–saturated flow induced by localized recharge in unconfined aquifers

2018 ◽  
Vol 22 (7) ◽  
pp. 3951-3963 ◽  
Author(s):  
Chia-Hao Chang ◽  
Ching-Sheng Huang ◽  
Hund-Der Yeh
Keyword(s):  
Soil Properties ◽  
Unsaturated Soil ◽  
Flow Model ◽  
Unsaturated Flow ◽  
Three Dimensional ◽  
Richards Equation ◽  
Coupled Flow ◽  
Saturated Flow ◽  
Flow Equations ◽  
Present Solution

Abstract. In the process of groundwater recharge, surface water usually enters an aquifer by passing an overlying unsaturated zone. Little attention has been given to the development of analytical solutions to a coupled unsaturated–saturated flow model due to localized recharge up to now. This paper develops a mathematical model to depict three-dimensional transient unsaturated–saturated flow in an unconfined aquifer with localized recharge on the ground surface. The model contains Richards' equation for unsaturated flow, a flow equation for saturated formation, and the Gardner constitutive model describing the behavior of unsaturated soil properties. Both flow equations are coupled through the continuity conditions of the head and flux at the water table. The semi-analytical solution to the coupled flow model is derived by the methods of Laplace transform and Fourier cosine transform. A sensitivity analysis is performed to explore the head response to the change in each of the aquifer parameters. A quantitative tool is presented to assess the recharge efficiency signifying the percentage of the water from the recharge to the aquifer. We found that the effect of unsaturated flow on the saturated hydraulic head is negligible if two criteria associated with the unsaturated soil properties and initial aquifer thickness are satisfied. The head distributions predicted from the present solution match well with those from finite-difference simulations. The predictions of the present solution also agree well with the observed data from a field experiment at an artificial recharge pond in Fresno County, California.

Characteristics of Dimensionless Pressure Gradients and Derivatives of Horizontal and Vertical Wells Completed within Inclined Sealing Faults

2021 ◽  
Author(s):  
A V Ogbamikhumi ◽  
E S Adewole
Keyword(s):  
Pressure Drop ◽  
Horizontal Well ◽  
Superposition Principle ◽  
Early Time ◽  
Pressure Gradients ◽  
Vertical Wells ◽  
Pressure Derivative ◽  
Vertical Well ◽  
Dimensionless Pressure ◽  
Horizontal And Vertical Wells

Abstract Dimensionless pressure gradients and dimensionless pressure derivatives characteristics are studied for horizontal and vertical wells completed within a pair of no-flow boundaries inclined at a general angle ‘θ’. Infinite-acting flow solution of each well is utilized. Image distances as a result of the inclinations are considered. The superposition principle is further utilized to calculate total pressure drop due to flow from both object and image wells. Characteristic dimensionless flow pressure gradients and pressure derivatives for the wells are finally determined. The number of images formed due to the inclination and dimensionless well design affect the dimensionless pressure gradients and their derivatives. For n images, shortly after very early time for each inclination, dimensionless pressure gradients of 1.151(N+1)/LD for the horizontal well and 1.151(N+1) for vertical well are observed. Dimensionless pressure derivative of (N+1)/2LD are observed for central and off-centered horizontal well locations, and (N+1)/2 for vertical well are observed. Central well locations do not affect horizontal well productivity for all the inclinations. The magnitudes of dimensionless pressure drop and dimensionless pressure derivatives are maximum at the farthest image distances, and are unaffected by well stand-off for the horizontal well.

Experimental and Numerical Investigation of Centrifugal Pump Performance When Handling Viscous Fluids

2005 ◽  
Author(s):  
M. H. Shojaee Fard ◽  
M. B. Ehghaghi ◽  
F. A. Boyaghchi
Keyword(s):  
Soviet Union ◽  
Centrifugal Pump ◽  
Turbulent Flows ◽  
Characteristic Curve ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Viscous Fluids ◽  
Test Bed ◽  
Flow Process ◽  
Pump Performance

On the test bed of centrifugal pump, the centrifugal pump performance has been investigated using water and viscous oil as Newtonian fluids, whose kinematic viscosities are 1 × 10−6, 43 × 10−6 and 62 × 10−6 m2/s, respectively. Also, the finite volume method is used to model the three dimensional viscous fluids for different operating conditions. For these numerical simulations the SIMPLEC algorithm is used for solving governing equations of incompressible viscous/turbulent flows through the pump. The κ-ε turbulence model is adopted to describe the turbulent flow process. These simulations have been made with a steady calculation and using the multiple reference frame (MRF) technique to take into account the impeller-volute interaction. Numerical results are compared with the experimental characteristic curve for each viscous fluid. The data obtained allow the analysis of the main phenomena existent in this pump, such as: head, efficiency, power and pressure field changes for different operating conditions. Also, the correction factors for oils are obtained from the experimental for part loading (PL), best efficiency point (BEP) and over loading (OL) and the results are compared with proposed factors by American Hydraulic Institute (HIS) and Soviet Union (USSR). The comparisons between the numerical and experimental results show a good agreement.

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