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Gour-tsyh Yeh

Gour-Tsyh (George) Yeh received his Ph.D. in hydrology from Cornell University in 1969 and M. S. in hydraulics from Syracuse University in 1967. His areas of specialty are hydrology, environmental fluid mechanics, hydraulics, and water resources. Dr. Yeh has extensive experience in multidisciplinary research, teaching, professional services, and coordination skills. He specializes in the mathematical formulation of complex physical transport and biogeochemical reactions and their computer implementations. His current research focuses on physics-based first principle approaches of watershed modeling, coupled surface and subsurface flow and transport processes, geochemical kinetics, biodegradation and micro-organism/geochemical interactions, geochemical equilibrium modelling, multi-phase flow and transport in both fractured and porous media, development of innovative numerical algorithms, and computational fluid dynamics. He has been actively promoting scientific knowledge exchange, crusading for technology transfer of sponsored research, and conducting workshops and short courses. He is a consultant to IAEA, United Nations. Achievements in his career include:

• developed over 130 physics-based process-level computational models: many of which has been adopted as the de facto standard by academic communities, federal agencies, and industries;
• achieved seminal advances in computational-models development and mathematical formulation of reactive transport (HYDROGEOCHEM series) that have been used by several university to produce quite a few PhD’s;
• accomplished the development of subsurface flow and contaminant transport models used worldwide in waste management and remediation (FEMWATER Series) and endorsed by US NRC, US EPA, and US Army Corps;
• developed the most used analytical groundwater contaminant transport that has been endorsed by EPA and more than 20 state agencies for assessing groundwater contamination extent (AT123D);
• served as review panelists for the US EPA STAR program for five times
• served as a member of the Florida governor’s technical advisory and review committee (TARC) on TMDL;
• conducted more than 50 interdisciplinary research projects with a total funding of over $17 Millions;
• published two books and more than 400 papers, technical reports, and conference proceedings and abstracts;
• received one presidential PIP award, one publication award, one NRC research associateship, one NRC senior research associateship, one outstanding research award, One distinguished researcher award, one graduate teaching award, and one outstanding alumni award;
• completed over 40 consulting jobs for over 30 clients nationally and internationally;
• offered short courses, seminars, and workshops many times on subsurface flow and reactive chemical transport;
• organized and chaired more than 20 important national and international symposia;
• gave more than 80 invited speeches nationally and internationally; and
• Supervised over 25 Ph.D. and M.S. students at Penn State and UCF in 20 years.
Phone: 886953673416
Address: No 300, Jhongda Road, Jhongli, Taoyuan, TAIWAN

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Papers by Gour-tsyh Yeh

WORLD SCIENTIFIC eBooks, Jun 1, 2004

ABSTRACT Highly nonlinear advection–dispersion-reaction equations govern numerous transport pheno... more ABSTRACT Highly nonlinear advection–dispersion-reaction equations govern numerous transport phenomena. Robust, accurate, and efficient algorithms to solve these equations hold the key to the success of applying numerical models to field problems. This paper presents the development and verification of a computational algorithm to approximate the highly nonlinear transport equations of reactive chemical transport and multiphase flow. The algorithm was developed based on the Lagrangian-Eulerian decoupling method with an adaptive ZOOMing and Peak/valley Capture (LEZOOMPC) scheme. It consists of both backward and forward node tracking, rough element determination, peak/valley capturing, and adaptive local grid refinement. A second-order tracking was implemented to accurately and efficiently track all fictitious particles. Shanks’ method was introduced to deal with slowly converging case. The accuracy and efficiency of the algorithm were verified with the Burger equation for a variety of cases. The robustness of the algorithm to achieve convergent solutions was demonstrated by highly nonlinear reactive contaminant transport and multiphase flow problems.

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Sep 20, 1999

The couplings among chemical reaction rates, advective and diffusive transport in fi-acjmredmedia... more The couplings among chemical reaction rates, advective and diffusive transport in fi-acjmredmedia or soils, and changes in hydraulic properties due to precipitation and dissolution within fractures andinrockmatrix are important for both nuclear waste disposal and remediation of contaminated sites. This paper describes the development and application of LEHGC2.0, a mechanistically-based numerical model for simulation of coupled fluid flow and reactive chemical transpo~including both fast and S1OW reactions invariably saturated media. Theoretical bases and numerical implementations are summarize& and two example problems are demonstrated. The fmt example deals with the effect of precipitation-dissolution on fluid flow and matrix diffusion in a two-dimensional 12actured media. Because of the precipitation and decreased difiion of solute from the fracture into the mat@ retardation in the fractured medium is not as large as the case wherein interactions beiween chemical reactions and transport are not considered. The second example focuses on a complicated but realistic advective-dispersive-reactive transport problem. This example exemplifies the need for innovative numerical algorithms to solve problems involving stiff geochemical reactions.

Journal of Earth Science & Climatic Change, Jul 4, 2015

T he development of subsurface media models and their applications to real-world problems has evo... more T he development of subsurface media models and their applications to real-world problems has evolved significantly since 1970's. This talk discusses the physical, chemical, biological, and mechanical processes that control the evolution of groundwater quantity, quality, and deformation as well as subsidence. These processes include multiphase flow of arbitrary number of phases, thermal transport, geo-mechanics, reactive transport, and propagation of electromagnetic waves as well as their interactions and feedbacks with the media. The advances of computational models centre on their increasing design capability to foster these coupling processes: from the simplest one-phase groundwater flow to the most complete aforementioned processes. Widely used models developed by academia, research institutes, government agencies, and private industries will be reviewed in terms of the processes included in the governing equations, types of boundary conditions, discretization methods, computational platform, and users' friendliness. Four computational models developed by the author will be briefed and example problems to groundwater management and remediation will be given.

The computer program HYDROGEOCHEM 4.0 is a coupled model of water flow, thermal transport, solute... more The computer program HYDROGEOCHEM 4.0 is a coupled model of water flow, thermal transport, solute transport, and geochemical kinetic/equilibrium reactions in saturated/unsaturated porous media in two dimensions, which is a modified version of HYDROGEOCHEM 3.0. The major modifications are: (1) the reformulation of reactive chemistry, in which a new paradigm of reaction-based approaches to biogeochemical processes was implemented; (2) heat transfer module was incorporated to allow the investigation on the effects of thermal transport on both fluid flows and reactive biogeochemical transport. It iteratively solves the two-dimensional fluid flow, heat transfer, and reactive chemical transport equations. The Richards equation is solved for fluid flow, the thermal transport equation is solved for heat transfer, and the advection-dispersion-reactive transport equations are solved for all mobile component equations and kinetic-variable equations. HYDROGEOCHEM 4.0 is designed for generic app...

Journal of Contaminant Hydrology

Environmental Studies, 1996

We review the modern mathematical-physical analysis of water movement in unsaturated soils, which... more We review the modern mathematical-physical analysis of water movement in unsaturated soils, which is central to understanding of the terrestrial segment of the hydrologie cycle. The relevant flow equation is a strongly nonlinear Fokker-Planck (convection-diffusion) equation. The theory of infiltration (the penetration into a soil mass of water made available at its surface) is described. Solutions fire developed for hillslope topographies. We deal primarily with ponded infiltration, but constant-rainfall infiltration is discussed also. The emphasis is on quasi-analytic and analytic solutions. Fully nonlinear solutions are developed, together with linearized solutions of certain problems. The nonlinear solutions involve either usefully convergent series or travelling waves. The linearizations use product solutions.

Geochemical Engineering Design (GED) is based on applications of the principles and various compu... more Geochemical Engineering Design (GED) is based on applications of the principles and various computer models that describe the biogeochemistry and physics of removal of contaminants from water by adsorption, precipitation and filtration. It can be used to optimize or evaluate the efficiency of all phases of in situ recovery (ISR). The primary tools of GED are reactive transport models; this talk describes the potential application of the HYDROGEOCHEM family of codes to ISR. The codes can describe a complete suite of equilibrium or kinetic aqueous complexation, adsorption-desorption, precipitation-dissolution, redox, and acid-base reactions in variably saturated media with density-dependent fluid flow. Applications to ISR are illustrated with simulations of (1) the effectiveness of a reactive barrier to prevent off-site uranium migration and (2) evaluation of the effect of sorption hysteresis on natural attenuation. In the first example, it can be seen that the apparent effectiveness ...

It is forecasted that two out of three persons in the world will be water stressed by the year of... more It is forecasted that two out of three persons in the world will be water stressed by the year of 2025 (EPA 1998). Proper management of water resources at watershed scale may offer the best solutions for water shortage and contamination. The objective of the research is to conduct reactive flow simulations in surface-subsurface, coupled flow systems using a high-performance version of WASH123D. WASH123D is a watershed hydrology simulator that utilizes the method of characteristics to solve land surface fluid dynamic equations and the Galerkin finite element method to solve subsurface groundwater flow equations. A Lagrangian-Eulerian finite element method is used to solve the reactive solute transport equations. Parallelisms of the high-performance WASH123D are implemented in MPI (Message Passing Interface) by using the parallel library PETSc. The goal is to evaluate the practicality of applying WASH123D to large realistic problems and to identify additional steps towards parallelism...

Journal of Hydraulic Engineering, 1985

Subregion Iteration of Finite Element Method for Large‐Field Problems of Ground‐Water Solute Tran... more Subregion Iteration of Finite Element Method for Large‐Field Problems of Ground‐Water Solute Transport. [Journal of Hydraulic Engineering 111, 547 (1985)]. Gour‐Tsyh Yeh, Jack C. Hwang, Woncheol C. cho. Abstract. To compute ...

Computational Methods in Water Resources: Volume 2, Proceedings of the XVth International Conference on Computational Methods in Water Resources, 2004

The parallel WASH123D, which is supported by the DoD CHSSI (Department of Defense Common High Per... more The parallel WASH123D, which is supported by the DoD CHSSI (Department of Defense Common High Performance Computing Software Support Initiative), is designed to solve watershed problems on scalable computing systems. WASH123D is a first-principle, physics-based model to compute water flow and/or contaminant and sediment transport within a watershed system. In the WASH123D model, a watershed is conceptualized as a coupled system of one-dimensional (1-D) channel network, two-dimensional (2-D) overland regime, and three-dimensional (3-D) subsurface media. It aims to address the environmental issues concerning both water quantity and quality. To reach numerical solutions with reasonable and tolerable computer time for simulations that embrace large meshes, numerical algorithm improvement and code parallelization are two essential tasks. Mathematically, 1-D channel flow and 2-D overland flow are described with the St. Venant equations, which are solved with either the Semi-Lagrangian or the Eulerian finite element method. The 3-D subsurface flow is governed by the modified Richards equation, which is solved with the Eulerian finite element method. The contaminant transport and sediment transport equations, which are solved with the Lagrangian-Eulerian finite element method, are derived based on the mass conservation principle. A parallel in-element particle-tracking algorithm for unsteady flow is applied to backtrack fictitious particles from global nodes to determine the so-called Lagrangian values when the Semi-Lagrangian or the Lagrangian-Eulerian method is used. This paper addresses the parallelization of such a complex numerical model. In phase I, tasks including data structure and software design, software tool development, as well as tool integration are accomplished. The 2- and 3-D flow modules are expected to be employed in the production stage.

International Journal for Numerical Methods in Engineering, 1996

A Lagrangian-Eulerian method with adaptively local ZOOMing and Peak/valley Capturing approach (LE... more A Lagrangian-Eulerian method with adaptively local ZOOMing and Peak/valley Capturing approach (LEZOOMPC), consisting of advection-diffusion decoupling, backward particle tracking, forward particle tracking, adaptively local zooming, peak/valley capturing and slave point utilization, is presented to solve two-dimensional advection-diffusion transport equations. This approach and the associated computer code, 2DLEZOOMPC, were developed to circumvent the difficulties associated with the EPCOF scheme, developed earlier by the authors, when it was extended from a one-dimensional space to a multidimensional space. In EPCOF, all the nodes, including global nodes and fine-grid nodes, of the previous time are forward tracked for both determining rough elements and exactly capturing peaks and valleys. After kicking off those unnecessary nodes, a subset of the forward-tracked nodes are activated to preserve the shape of spatial distribution of the quantity of interest (e.g. concentration in the solute transport). The accurate results of applying EPCOF to solving two one-dimensional benchmark problems under a variety of conditions have shown the capability of this scheme to eliminate all types of numerical errors associated with the advection term and to keep the maximum computational error to be within the prescribed error tolerance. However, difficulties arose when the EPCOF scheme was extended to a multidimensional space mainly due to the geometric difference between a one-dimensional space and a multi-dimensional space. To avoid these geometric difficulties, we modified the EPCOF scheme and named the modified scheme LEZOOMPC. LEZOOMPC uses regularly local zooming for rough elements and peak/valley capturing within subelements to resolve the problems of triangulation and boundary source as well as to preserve the shape of concentration distribution. In addition, LEZOOMPC employs the concept of slave points to deal with the compatibility problem associated with the diffusion zooming in a multi-dimensional space. As a result, not only is the geometrical problem resolved, but also the spirit of EPCOF is retained. Application of 2DLEZOOMPC to solving three two-dimensional benchmark problems indicates it yields extremely accurate results for all the test cases. ZDLEZOOMPC could solve advection-diffusion transport problems accurately to within any prescribed error tolerance by using mesh Peclet numbers ranging from 0 to co and very large time-step sizes as well as coarse global grid sizes. The size of time-step is related to both the diffusion coefficients and mesh sizes. Hence, it is limited only by the diffusion solver. Extension of this approach to a three-dimensional space will contain only implementation complexity but neither conceptual nor implementation difficulties. Details of the three-dimensional computer code, 3DLEZOOMPC, is to be presented in the companion paper.

... Element Discretization for Problem 3 224 Comparison of FEWA Simulation and Exact ... governin... more ... Element Discretization for Problem 3 224 Comparison of FEWA Simulation and Exact ... governing equations of subsurface fluid flows, as well as solute and thermal ... convection/advection conduction or diffusion compaction/consolidation Chemical transport Concentration Same as ...

Water Resources Research, 1991

Transferable discharge permit (TDP) programs for controlling several pollutants may manage such p... more Transferable discharge permit (TDP) programs for controlling several pollutants may manage such pollutants as several individual commodities or as a single weighted sum of the various pollutants. This paper shows that the weighted sum permit program may be appropriate for managing pollutants that have an additive or a noninteractive effect on environmental quality. However, under this approach, administrators do not have direct control over the amount of each pollutant that is discharged, and environmental quality may be jeopardized unless the selected weighting factors induce a market equilibrium that satisfies environmental quality standards for the region. Estimates of the cost‐effective weighting factors that would tend to satisfy environmental quality standards under such programs are developed here. These estimates require complete water quality information and, in the case of noninteractive pollutants, treatment costs. An approach is described for estimating the cost‐effectiv...