The Experts below are selected from a list of 45315 Experts worldwide ranked by ideXlab platform
Jin Liu - One of the best experts on this subject based on the ideXlab platform.
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On the coupled unSaturated–Saturated Flow process induced by vertical, horizontal, and slant wells in unconfined aquifers
Hydrology and Earth System Sciences, 2017Co-Authors: Xiuyu Liang, Hongbin Zhan, You-kuan Zhang, Jin LiuAbstract: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.
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On Coupled UnSaturated-Saturated Flow Process Induced by Vertical, Horizontal and Slant Wells in Unconfined Aquifers
2016Co-Authors: Xiuyu Liang, Hongbin Zhan, You-kuan Zhang, Jin LiuAbstract: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.
Hongbin Zhan - One of the best experts on this subject based on the ideXlab platform.
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Quantification of transient specific yield considering unSaturated-Saturated Flow
Journal of Hydrology, 2020Co-Authors: Dawei Cheng, Wenke Wang, Hongbin Zhan, Zaiyong Zhang, Li ChenAbstract:Abstract Specific yield is one of the most important hydrogeological parameters, and is a key factor connecting Flow processes in the unSaturated and Saturated zones. In this study, an innovative expression for the dynamic (or time-dependent) specific yield is proposed considering the coupled unSaturated-Saturated Flow process. The new specific yield equation includes parameters such as Saturated water content, residual water content, pore characteristic parameter, initial depth of water table, time-dependent depth of water table, initial pressure head, and time. The involving parameters in this new specific yield equation reflect the impacts of lithology, initial water table depth and other factors. This new equation approaches an asymptotic (steady-state) value which is the same as reported previously for a shallow water table condition. Both advective and diffusive unSaturated Flow processes are taken into consideration, which is in contrast to a previous study that ignored the diffusive unSaturated Flow process. The model established in this study reveals the complete dynamic process of variation of water content and water head in the unSaturated zone. The newly developed specific yield equation can be incorporated into groundwater Flow theory considering a dynamic water table reflective of a physically based unSaturated-Saturated Flow process.
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On the coupled unSaturated–Saturated Flow process induced by vertical, horizontal, and slant wells in unconfined aquifers
Hydrology and Earth System Sciences, 2017Co-Authors: Xiuyu Liang, Hongbin Zhan, You-kuan Zhang, Jin LiuAbstract: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.
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On Coupled UnSaturated-Saturated Flow Process Induced by Vertical, Horizontal and Slant Wells in Unconfined Aquifers
2016Co-Authors: Xiuyu Liang, Hongbin Zhan, You-kuan Zhang, Jin LiuAbstract: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.
Carol S. Woodward - One of the best experts on this subject based on the ideXlab platform.
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An accelerated Picard method for nonlinear systems related to variably Saturated Flow
Advances in Water Resources, 2012Co-Authors: P.a. Lott, Carol S. Woodward, Homer F. Walker, Ulrike Meier YangAbstract:In this paper, we investigate the effectiveness of the Anderson acceleration method applied to modified Picard iteration for nonlinear problems arising in variably Saturated Flow modeling. While many authors have studied the relative merits of Newton’s method and modified Picard iteration in this context, the combination of Anderson acceleration and modified Picard iteration has not been investigated for these problems until recently. Since modified Picard iteration can be slow to converge, we investigate the use of Anderson acceleration to provide faster convergence while maintaining the robustness and lower memory requirements of modified Picard iteration relative to Newton’s method. Results indicate that Anderson acceleration significantly improves not only convergence speed but also robustness of modified Picard iteration and can often provide faster solutions than Newton’s method without the need for derivative computations.
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Applications of Sensitivity Analysis to Uncertainty Quantification in Variably Saturated Flow
Computational Methods in Water Resources Proceedings of the XIVth International Conference on Computational Methods in Water Resources (CMWR XIV), 2002Co-Authors: Carol S. Woodward, K. E. Grant, Reed M. MaxwellAbstract:In this paper, we present results demonstrating the effectiveness of a sensitivity analysis approach to uncertainty quantification of a variably Saturated Flow model. The basis for our method is a software system which simultaneously solves for solutions of large-scale nonlinear systems of equations and the sensitivity of the solutions to selected parameters. We present test cases showing the effects on the relative uncertainty of pressure due to heterogeneity in the absolute permeability and to differences in parameterizing the Van Genuchten curve soil parameters, α and n .
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newton krylov multigrid solvers for large scale highly heterogeneous variably Saturated Flow problems
Advances in Water Resources, 2001Co-Authors: Jim E. Jones, Carol S. WoodwardAbstract:In this paper, we present a class of solvers developed for the parallel solution of Richards' equation, a model used in variably Saturated Flow simulations. These solvers take advantage of the fast, robust convergence of globalized Newton methods as well as the parallel scalability of multigrid preconditioners. We compare two multigrid methods. The methods differ primarily in their handling of discontinuous and anisotropic permeability fields, with one method invoking a simple pointwise smoothing technique and the other a more expensive plane smoother. Computational results are presented to show the effectiveness of the entire nonlinear solution procedure, to demonstrate the effect of discontinuities and anisotropies, and to explore parallel efficiencies.
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Newton–Krylov-multigrid solvers for large-scale, highly heterogeneous, variably Saturated Flow problems
Advances in Water Resources, 2001Co-Authors: Jim E. Jones, Carol S. WoodwardAbstract:In this paper, we present a class of solvers developed for the parallel solution of Richards' equation, a model used in variably Saturated Flow simulations. These solvers take advantage of the fast, robust convergence of globalized Newton methods as well as the parallel scalability of multigrid preconditioners. We compare two multigrid methods. The methods differ primarily in their handling of discontinuous and anisotropic permeability fields, with one method invoking a simple pointwise smoothing technique and the other a more expensive plane smoother. Computational results are presented to show the effectiveness of the entire nonlinear solution procedure, to demonstrate the effect of discontinuities and anisotropies, and to explore parallel efficiencies.
Xiuyu Liang - One of the best experts on this subject based on the ideXlab platform.
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On the coupled unSaturated–Saturated Flow process induced by vertical, horizontal, and slant wells in unconfined aquifers
Hydrology and Earth System Sciences, 2017Co-Authors: Xiuyu Liang, Hongbin Zhan, You-kuan Zhang, Jin LiuAbstract: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.
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On Coupled UnSaturated-Saturated Flow Process Induced by Vertical, Horizontal and Slant Wells in Unconfined Aquifers
2016Co-Authors: Xiuyu Liang, Hongbin Zhan, You-kuan Zhang, Jin LiuAbstract: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.
R. Rozenblit - One of the best experts on this subject based on the ideXlab platform.
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Effect of surfactant concentration on Saturated Flow boiling in vertical narrow annular channels
International Journal of Multiphase Flow, 2007Co-Authors: Gad Hetsroni, M. Gurevich, Albert Mosyak, R. RozenblitAbstract:Saturated Flow boiling of environmentally acceptable nonionic surfactant solutions of Alkyl (8–16) was compared to that of pure water. The concentration of surfactant solutions was in the range of 100–1000 ppm. The liquid Flowed in an annular gap of 2.5 and 4.4 mm between two vertical tubes. The heat was transferred from the inner heated tube to two-phase Flow in the range of mass flux from 5 to 18 kg/m 2 s and heat flux from 40 to 200 kW/m 2 . Boiling curves of water were found to be heat flux and channel gap size dependent but essentially mass flux independent. An addition of surfactant to the water produced a large number of bubbles of small diameter, which, at high heat fluxes, tend to cover the entire heater surface with a vapor blanket. It was found that the heat transfer increased at low values of relative surfactant concentration C/C0, reaches a maximum close to the value of C/C0 = 1 (where C0 = 300 ppm is the critical micelle concentration) and decreased with further increase in the amount of additive. The dependence of the maximal values of the relative heat transfer enhancement, obtained at the value of relative concentration of C/C0 = 1, on the boiling number Bo may be presented as single curve for both gap sizes and the whole range of considered concentrations. 2007 Elsevier Ltd. All rights reserved.
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Saturated Flow boiling heat transfer of environmentally acceptable surfactants
International Journal of Multiphase Flow, 2004Co-Authors: Gad Hetsroni, Jacques L. Zakin, M. Gurevich, Albert Mosyak, E. Pogrebnyak, R. RozenblitAbstract:Saturated Flow boiling of surfactant solutions was studied and compared to that of pure water. The liquid Flowed in an annular space between two vertical tubes. The heat was transferred from the inner heated tube to the outer one. A nonionic surfactant, with negligible environmental impact, was used. The surface tension for the water–surfactant system was determined at various temperatures. High-speed photography was used for direct observation of the sequence of events that occur during Flow boiling. The heat transfer experiments focused on the Saturated boiling regime. Addition of surfactant to water produced a large number of small diameter bubbles, which, at high heat fluxes, tend to cover the entire heater surface with a vapor blanket. Boiling heat transfer coefficients in surfactant solution are higher than that in pure water. � 2004 Elsevier Ltd. All rights reserved.
