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HYDROGEOCHEM 4.0 是實用的流體流動、熱傳遞耦合模型，可以通過飽和-非飽和介質的HYDROGEOCHEMical 傳輸。HYDROGEOCHEM 5.0將模型升級為三維模式。
HYDROGEOCHEM 4.0：通過飽和-不飽和介質的流體流動，熱傳輸和水文地球化學耦合模型
HYDROGEOCHEM 4.0計算機程序是二維的飽和/不飽和多孔介質中水流，熱傳輸，溶質傳輸和地球化學動力學/平衡反應的耦合模型。
HYDROGEOCHEM 5.0：在可變飽和條件下流體流動，熱傳輸和水化地球化學耦合的三維模型
HYDROGEOCHEM 5.0計算機程序是在飽和/不飽和介質中的流體流動，熱傳輸，水文傳輸和生物地球化學動力學/平衡反應的數值模型。它是二維HYDROGEOCHEM 4.0的三維版本。
水文地球化學簡介
HYDROGEOCHEM的目的是模擬瞬態(tài)和/或穩(wěn)態(tài)密度相關的流場和溫度分布，并計算地下介質中反應性多種化學濃度的瞬態(tài)和/或穩(wěn)態(tài)分布。
HYDROGEOCHEM可以在完全飽和，完全不飽和，部分不飽和或部分飽和的地下介質的三維平面上計算和預測壓頭，含水量，流速和總壓頭的分布。它還可以計算和預測多種化學成分的時空分布。介質可以根據需要由具有不同材料屬性的多種類型的土壤和地質單元組成。每種土壤類型可以是各向同性或各向異性的。控制化學分布分布的過程包括（1）水絡合，還原-氧化，吸附以及沉淀和溶解的地球化學平衡，以及（2）通過對流，分散和不飽和作用的水文輸送。
在適當的初始邊界條件和四種邊界條件的約束下，利用Galerkin有限元方法模擬了控制不飽和介質中壓力分布和水流的廣義Richards方程和Darcy定律。根據質量守恒原理推導水文輸運方程（一組PDE），并基于質量平衡和質量作用推導地球化學平衡方程（一組AE）。PDE和AE的耦合集是使用常規(guī)有限元方法或具有峰值捕獲方案的混合Langrangian-Eulerian有限元方法來模擬的，這些方法受適當的初始邊界條件和四種邊界條件的影響。六面體元素，三棱柱，
HYDROGEOCHEM是飽和-不飽和介質中水文傳輸和地球化學反應的耦合模型。它旨在模擬Na，水成分的瞬態(tài)和/或穩(wěn)態(tài)傳輸以及Ns吸附劑成分和離子交換部位的瞬態(tài)和/或穩(wěn)態(tài)質量平衡。HYDROGEOCHEM沿著運輸路徑計算N組分物種，Mx復雜物種，My吸附物種的物種分布。Mz離子交換物質和Mp可能沉淀的物質。物理，水文和化學設置如下。
介質：非均質和各向異性。
流量條件：飽和-不飽和流量。
水文過程：對流，擴散和擴散。
化學過程：水絡合，吸附/解吸（表面絡合，恒定電容和雙層方法），離子交換，沉淀/溶解，氧化還原和酸堿反應。
源/接收器：時空相關元素和點源/接收器。
初始條件：指定的初始條件或模擬的穩(wěn)態(tài)解作為初始條件。
邊界條件：Dirichlet邊界上規(guī)定的總分析濃度，流入邊界上規(guī)定的通量，流出邊界上的自然推測通量-所有邊界值（濃度或通量）在空間上和時間上都是依賴的。
數值離散：具有四邊形元素，三角形元素或這兩種類型的混合物的有限元方法。
近似選項：矩陣或質量塊一致，用于表面和元素積分的節(jié)點正交或高斯正交。
求解器：直接帶矩陣求解器，基本點迭代和4種PCG方法（多項式PCG，不完全Cholesky PCG，修改的不完全Cholesky PCG和對稱連續(xù)超松弛PCG）。
時間步長：隱式差異，Crank-Nicholson中心差異或中間差異。
地球化學反應的求解方法：牛頓-拉夫遜全旋轉解雅可比矩陣方程式和物種濃度約束。
HYDROGEOCHEM是可用于模擬反應性多物種-多組分化學物質通過飽和-不飽和介質傳輸的模型。它不是路徑模型；它不是路徑模型。它是一個真實的運輸模型，并伴有均相和異質地球化學反應。
水文地球化學的特殊功能
HYDROGEOCHEM的特殊之處在于它在建模方面的靈活性和多功能性，從而解決了盡可能多的問題。該模型旨在（1）處理異質和各向異性介質，（2）考慮時空分布以及點源/匯，（3）接受規(guī)定的初始條件或通過模擬穩(wěn)態(tài)版本獲得初始條件（4）處理分布在Dirichlet邊界上的規(guī)定瞬態(tài)濃度，（5）處理可變邊界上的時間相關通量，（6）處理Cauchy邊界上的時間相關總通量，
水文化學輸入
（1）就節(jié)點和元素而言的幾何形狀，以及就節(jié)點和片段而言的邊界；（2）土壤特性，包括：（a）飽和水力傳導率或滲透率；（b）水和介質的可壓縮性；（c）堆密度；（d）每種土壤或地質單位的三種土壤特性曲線，即保留曲線，相對電導率與水頭曲線以及水容量曲線；（e）影響孔隙率；（f）每種土壤類型或地質單位的分散度和有效分子擴散系數；（3）壓頭在感興趣區(qū)域的初始分布；（4）凈降水量，允許的積水深度，潛在的蒸發(fā)以及允許的土壤小壓頭；（5）在狄利克雷邊界上的規(guī)定頭；（6）在柯西和/或諾伊曼邊界上的規(guī)定通量；（七）人工取水或注水；（8）化學成分數目，化學種類及其熱力學數據庫；（9）人工水/水和所有化學成分的水槽；（10）在狄利克雷邊界上規(guī)定的所有化學成分的總濃度；（11）在可變邊界上規(guī)定的所有化學成分的通量；（12）所有化學成分濃度的初始分布。項目4到11中的所有輸入都可以是時間相關的或隨時間變化的。（11）在可變邊界上規(guī)定的所有化學成分的通量；（12）所有化學成分濃度的初始分布。項目4到11中的所有輸入都可以是時間相關的或隨時間變化的。（11）在可變邊界上規(guī)定的所有化學成分的通量；（12）所有化學成分濃度的初始分布。項目4到11中的所有輸入都可以是時間相關的或隨時間變化的。
水文化學輸出
（1）在任何期望的時間在二維網格上的壓頭，總壓頭，含水量和流速；（2）在任何需要的時間通過各種邊界的水通量和介質中積累的水量；（3）在任何需要的時間在三維網格上分布所有化學成分的總分析濃度，總溶解濃度，總吸附濃度，總沉淀濃度和自由離子濃度；（4）通過可變邊界的廢物通量；（5）等效kds作為感興趣區(qū)域中時間和空間的函數。
HYDROGEOCHEM要求：具有16 MB RAM和FORTRAN編譯器的Pentium，任何工作站，例如IBM RS6000，DEC Alpha，Silicon Graphics，Sun SparcStation和HP 9000系列。
【英文介紹】
HYDROGEOCHEM 4.0:
A Coupled Model of Fluid Flow, Thermal Transport, and HYDROGEOCHEMical Transport through Saturated-Unsaturated Media
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.
HYDROGEOCHEM 5.0:
A Three-Dimensional Model of Coupled Fluid Flow, Thermal Transport, and HYDROGEOCHEMical Transport through Variably Saturated Conditions
The computer program HYDROGEOCHEM 5.0 is a numerical model of fluid flow, thermal transport, hydrologic transport, and biogeochemical kinetic/equilibrium reactions in saturated/unsaturated media. It is a three-dimensional version of the two-dimensional HYDROGEOCHEM 4.0.
INTRODUCTION TO HYDROGEOCHEM
The purpose of HYDROGEOCHEM is to simulate transient and/or steady-state density-dependent flow fields and temperature distribution and to compute transient and/or steady-state distribution of reactive multispecies chemical concentrations in subsurface media.
HYDROGEOCHEM computes and predicts the distribution of pressure head, moisture content, flow velocity, and total head over a three-dimensional plane in either completely saturated, completely unsaturated, partially unsaturated, or partially saturated subsurface media. It also computes and predicts the spatial-temporal distribution of multi-chemical components. The media may consist of as many types of soils and geologic units as desired with different material properties. Each soil type may be isotropic or anisotropic. The processes governing the distribution of chemical distribution include (1) geochemical equilibrium of aqueous complexation, reduction-oxidation, sorption, and precipitation and dissolution, and (2) hydrological transport by flow advection, dispersion, and effect of unsaturation.
The generalized Richards' equation and Darcy's law governing pressure distribution and water flow in saturated-unsaturated media are simulated with the Galerkin finite-element method subject to appropriate initial and four types of boundary conditions. The hydrological transport equations (a set of PDEs) are derived based on the principle of conservation of mass, and the geochemical equilibrium equations (a set of AEs) are derived based on the mass balance and mass action. The coupled set of PDEs and AEs are simulated with either the conventional finite-element methods or the hybrid Langrangian-Eulerian finite-element method with peak capturing scheme subject to appropriate initial and four types of boundary conditions. Hexahedral elements, triangular prism, and tetrahedral elements are used to facilitate the discretization of the region of interest.
HYDROGEOCHEMis a coupled model of hydrologic transport and geochemical reaction in saturated-unsaturated media. It is designed to simulate transient and/or steady-state transport of Na, aqueous components and transient and/or steady-state mass balance of Ns adsorbent components and ion-exchange sites. Along the transport path, HYDROGEOCHEM computes the species distribution of N componentspecies, Mx complexed species, My adsorbed species. Mz ion-exchanged species, and Mp potentially precipitated species. The physical, hydrological and chemical settings are as follows.
Media:Heterogeneous and Anisotropic.
Flow Conditions:Saturated-Unsaturated Flows.
Hydrologic Processes:Advection, Dispersion and Diffusion.
Chemical Processes:Aqueous Complexation, Adsorption/Desorption (Surface Complexation, Constant Capacitance, and Double Layer Approaches), Ion-Exchange, Precipitation/Dissolution, Redox, and Acid-Base Reactions.
Source/Sink:Spatially- and Temporally-Dependent Element and Point Sources/Sinks.
Initial Conditions:Prescribed Initial Condition or the Simulated Steady-State Solution as the Initial Condition.
Boundary Conditions:Prescribed Total Analytical Concentrations on Dirichlet Boundaries, Prescribed Fluxes on Flow-In Boundaries, Natural Advective Fluxes on Flow-Out Boundaries - All Boundary Values (Concentrations or Fluxes) are Spatially- and Temporally-Dependent.
Numerical Discretization:Finite-Element Methods with Quadrilateral Elements, Triangular Elements, or the Mixtures of These Two Types.
Approximation Options:Consistent Matrix or Mass Lumping, Nodal Quadrature or Gaussian Quadrature for Surface and Element Integrations.
Solvers:Direct Band Matrix Solver, Basic Point Iterations, and 4 PCG Methods (polynomial PCG, Incomplete Cholesky PCG, Modified Incomplete Cholesky PCG, and Symmetric Successive Over-Relaxation PCG).
Time Stepping:Implicit Difference, Crank-Nicholson Central Difference, or Mid-Difference.
Solution Methods for Geochemical Reactions:Newton-Raphson with Full Pivoting to Solve the Jacobian Matrix Equation and Constraints on Species Concentrations.
HYDROGEOCHEM is the only commercially-available model for the simulation of reactive multispecies-multicomponent chemical transport through saturated-unsaturated media. It is not a path model; it is a true transport model coupled with homogeneous and heterogeneous geochemical reactions.
HYDROGEOCHEM SPECIAL FEATURES
The special features of HYDROGEOCHEM are its flexibility and versatility in modeling as wide a range of problems as possible. The model is designed to (1) treat heterogeneous and anisotropic media, (2) consider spatially and temporally-distributed as well as point sources/sinks, (3) accept the prescribed initial conditions or obtain initial conditions by simulating the steady-state version of the system under consideration, (4) deal with prescribed transient concentrations distributed over a Dirichlet boundary, (5) handle time-dependent fluxes over variable boundaries, (6) deal with time-dependent total fluxes over Cauchy boundaries, (7) include the off-diagonal dispersion coefficient tensor components in the governing equation for dealing with cases when the coordinate system does not coincide with the principal directions of the dispersion coefficient tensor, (8) provide two options for treating the mass matrix - consistent and lumping, (9) give three options (exact relaxation, under- and over-relaxation) for estimating the nonlinear matrix, (10) include two options (direct solution with Gaussian elimination method and successive point iterations) for solving the linearized matrix equations, (11) include both quadrilateral and triangular elements to facilitate the discretization of the region, (12) automatically reset time step size when boundary conditions or sources/sinks change abruptly, and (13) include simultaneous chemical processes of aqueous complexation, precipitation/dissolution, adsorption, ion exchange, redox, and acid-base reactions.
HYDROGEOCHEM INPUT
(1) Geometry in terms of nodes and elements, and boundaries in terms of nodes and segments; (2) soil properties including (a) saturated hydraulic conductivities or permeabilities; (b) compressibility of water and the media, respectively; (c) bulk density; (d) three soil characteristic curves for each type of soil or geologic unit which are the retention curve, relative conductivity vs head curve, and water capacity curve; (e) effect porosity; and (f) dispersivities, and effective molecular diffusion coefficient for each soil type or geologic unit; (3) initial distribution of pressure head over the region of interest; (4) net precipitation, allowed ponding depth, potential evaporation, and allowed minimum pressure head in the soil; (5) prescribed head on Dirichlet boundaries; (6) prescribed fluxes on Cauchy and/or Neumann boundaries; (7) artificial withdrawals or injections of water; (8) number of chemical components as well as chemical species and their thermodynamic data base; (9) artificial sources/sinks of water and all chemical components; (10) prescribed total concentrations of all chemical components on Dirichlet boundaries; (11) prescribed fluxes of all chemical components on variable boundaries; and (12) initial distribution of all chemical component concentrations. All inputs in items 4 through 11 can be time-dependent or constant with time.
HYDROGEOCHEM OUTPUT
(1) pressure head, total head, moisture content, and flow velocity over the two-dimensional grid at any desired time; (2) water fluxes through all types of boundaries and amount of water accumulated in the media at any desired time; (3) distribution of total analytical concentrations, total dissolved concentrations, total sorbed concentrations, total precipitated concentrations, and free ion concentrations of all chemical components over a three-dimensional grid at any desired time; (4) amount of waste fluxes through the variable boundary; and (5) equivalent kds as a function of time and space in the region of interest.
HYDROGEOCHEM Requirements:Pentium with 16 MB RAM and FORTRAN Compiler, any Workstation, e.g., IBM RS6000, DEC Alpha, Silicon Graphics, Sun SparcStation, and HP 9000 Series.
