Browsing by Author "Yeh, LM"

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A locally conservative Eulerian-Lagrangian numerical method and its application to nonlinear transport in porous media
(2000)
Douglas, J
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Pereira, F
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Yeh, LM
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應用數學系
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Department of Applied Mathematics
Eulerian-Lagrangian and Modified Method of Characteristics (MMOC) procedures provide computationally efficient techniques for approximating the solutions of transport-dominated diffusive systems. The original MMOC fails to preserve certain integral identities satisfied by the solution of the differential system; the recently introduced variant, called the MMOCAA, preserves the global form of the identity associated with conservation of mass in petroleum reservoir simulations, but it does not preserve a localized form of this identity. Here, we introduce an Eulerian-Lagrangian method related to these MMOC procedures that guarantees conservation of mass locally for the problem of two-phase, immiscible, incompressible flow in porous media. The computational efficiencies of the older procedures are maintained. Both the original MMOC and the MMOCAA procedures for this problem are derived from a nondivergence form of the saturation equation; the new method is based on the divergence form of the equation. A reasonably extensive set of computational experiments are presented to validate the new method and to show that it produces a more detailed picture of the local behavior in waterflooding a fractally heterogeneous medium. A brief discussion of the application of the new method to miscible flow in porous media is included.
Convergence of a dual-porosity model for two-phase flow in fractured reservoirs
(2000-06-01)
Yeh, LM
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應用數學系
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Department of Applied Mathematics
A dual-porosity model describing two-phase, incompressible, immiscible hows in a fractured reservoir is considered. Indeed, relations among fracture mobilities, fracture capillary presure, matrix mobilities, and matrix capillary presure of the model are mainly concerned. Roughly speaking, proper relations for these functions are (1) Fracture mobilities go to zero slower than matrix mobilities as fracture and matrix saturations go to their limits, (2) Fracture mobilities times derivative of fracture capillary presure and matrix mobilities times derivative of matrix capillary presure are both integrable functions. Galerkin's method is used to study this problem. Under above two conditions, convergence of discretized solutions obtained by Galerkin's method is shown by using compactness and monotonicity methods. Uniqueness of solution is studied by a duality argument. Copyright (C) 2000 John Wiley & Sons, Ltd.
On a steady state Euler-Poisson model for semiconductors
(1996)
Yeh, LM
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交大名義發表
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應用數學系
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National Chiao Tung University
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Department of Applied Mathematics
On two-phase flow in fractured media
(2002-08-01)
Yeh, LM
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應用數學系
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Department of Applied Mathematics
A model describing two-phase, incompressible, immiscible flow in fractured media is discussed. A fractured medium is regarded as a porous medium consisting of two superimposed continua, a continuous fracture system and a discontinuous system of medium-sized matrix blocks. Transport of fluids through the medium is primarily within the fracture system. No flow is allowed between blocks, and only matrix-fracture flow is possible. Matrix block system plays the role of a global source distributed over the entire medium. Two-phase flow in a fractured medium is strongly related to phase mobilities and capillary pressures. In this work, four relations for these functions axe presented, and the existence of weak solutions under each relation will also be shown.
Subsonic solutions of hydrodynamic model for semiconductors
(1997-11-10)
Yeh, LM
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交大名義發表
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應用數學系
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National Chiao Tung University
;
Department of Applied Mathematics
This paper is concerned with the existence and uniqueness of the steady-state solution of hydrodynamic model for semiconductor devices. Boundary conditions are prescribed by vorticity on inflow boundary as well as by electron density, temperature, and normal component of electron velocity on whole boundary. If the ambient temperature is large, and if both vorticity on inflow boundary and the variation of density on boundary are small, a unique subsonic solution exists. (C) 1997 by B.G. Teubner Stuttgart-John Wiley & Sons Ltd.
Well-posedness of the hydrodynamic model for semiconductors
(1996-12-01)
Yeh, LM
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交大名義發表
;
應用數學系
;
National Chiao Tung University
;
Department of Applied Mathematics
This paper concerns the well-posedness of the hydrodynamic model for semiconductor devices, a quasi-linear elliptic-parbolic-hyperbolic system. Boundary conditions for elliptic and parabolic equations are Dirichlet conditions while boundary conditions for the hyperbolic equations are assumed to be well-posed in L(2) sense. Maximally strictly dissipative boundary conditions for the hyperbolic equations satisfy the assumption of well-posedness in L(2) sense. The well-posedness of the model under the boundary conditions is demonstrated.
Well-posedness of the hydrodynamic model for semiconductors
(1996-12-01)
Yeh, LM
;
應用數學系
;
Department of Applied Mathematics
This paper concerns the well-posedness of the hydrodynamic model for semiconductor devices, a quasi-linear elliptic-parbolic-hyperbolic system. Boundary conditions for elliptic and parabolic equations are Dirichlet conditions while boundary conditions for the hyperbolic equations are assumed to be well-posed in L(2) sense. Maximally strictly dissipative boundary conditions for the hyperbolic equations satisfy the assumption of well-posedness in L(2) sense. The well-posedness of the model under the boundary conditions is demonstrated.