This article is translated by China Science Software Network
HYDRUS Software Introduction--Water Flow and Solute Transport Simulation Software
HYDRUS is an environmental simulation software running on Windows. It is mainly used for water flow and solute transport in variable saturated porous media. HYDRUS includes two-dimensional and three-dimensional finite element calculations for water, heat and multisolute transport in saturated porous media, including a parameter optimization algorithm for the inverse estimation of water pressure and solute transport parameters for various soils. . The model interacts with a graphical interface for data pre-processing, structured and unstructured finite element mesh generation, and graphical representation of the results.
There are five versions of HYDRUS, and users can choose the version that works best for them. Users can choose 2D applications that are limited to general functionality (2D-Standard version, consistent with previous Hydrus-2D functionality with MeshGen-2D) or 2D and 3D applications (such as 3D-Standard or 3D-Professional). Users can also choose relatively simple (two-dimensional right-angle geometry - 3D-Lite, consistent with the previous Hydrus-2D function without MeshGen-2D) or three-dimensional geometric solid graphics - 3D-Lite) or more complex geometry ( 2D-Standard for common 2D geometry or 3D-Standard for 2D and Layer 3D, and 3D-Professional for general 3D geometry. Users can also choose to upgrade from a lower version to a higher version.
Standard calculation model
HYDRUS is a finite element calculation model for the two-dimensional and three-dimensional motion of water, heat and polysols in a saturated porous medium. The HYDRUS numerical solution solves the Richards equation for saturated unsaturated water flow and the convection-diffusion equation for heat transfer and solute transport.
The water flow equation contains a sinking period that causes the plant roots to absorb water. The heat transfer equation takes into account water flow and convection motion. The management of convective transport equations for convective diffusion is a very common form, including the regulation of solid and liquid nonlinear non-equilibrium reactions and the linear equilibrium reaction of liquids and gases. Therefore, both adsorbed solutes and volatile solutes (such as insecticides) have been considered. The solute transport equation also includes the effects of zero-order production, independent primary degradation of other solutes, and first-order attenuation and production reactions to provide the desired coupling between the solute in successive primary chains. Migration simulation also causes liquid relative flow and diffusion, gas phase diffusion, so the secondary model can simultaneously simulate solute transport under liquid and gaseous conditions. At present, HYDRUS can consider up to 15 kinds of solute, which are coupled in a unidirectional chain or independently transported between solute. Physical non-equilibrium solute transport is caused by the two-zone and double-porosity equations, and divides the liquid phase into moving and non-movable regions. The theory of attachment and separation, including filtration theory, is also included in the simulation of viral, colloidal and bacterial migration.
HYDRUS can be used to analyze the movement of water and solutes in unsaturated, partially saturated or saturated porous media. HYDRUS can treat the water flow area by irregular boundaries, and the water flow area itself may be composed of non-uniform soil with local anisotropy. Water flow and migration may occur in a vertical plane, or in a horizontal plane, with a vertical axis or a three-dimensional region with radial symmetry.
The water flow portion of the model can be used to process continuous or time-varying defined direction and flow boundaries, as well as boundaries controlled by meteorological conditions. Soil surface boundary conditions may change during simulations from a given flow to a specified direction type condition, and vice versa. It also handles the free surface boundary by the amount of water remaining in the saturated portion of the water and the undrained boundary conditions. Node drainage is represented by a simple simulated experimental relationship.
For solute transport, the software supports both continuous and varying defined concentrations (Dirichlet or first-type) as well as concentration flux boundaries (Cauchy or third-type). The diffusion tensor contains the effects of molecular diffusion and tortuosity.
The hydrological properties of unsaturated soils are summarized by the following theories: vanGenuchten in 1980, Brooks and Corey in 1964, Durner in 1994, Kosugi in 1995, and the modified analytic function of vanGenuchten. These amendments further describe the water properties near saturation. The HYDRUS software contains hysteresis combined with empirical simulations introduced by Scottetal in 1983 and Kool and Parker in 1987.
This model assumes that the dry scan curve is derived from the main drying curve and that the wet scan curve is derived from the main wetting curve. HYDRUS also includes Lenhard et al. in 1991 and Lenhard and Parker's hysteretic model in 1992, which eliminates pumps by tracking historical reversal points. HYDRUS's scaling process in a given soil environment has reached an approximate hydraulic change, involving a set of linear scale change tools that relate to the relationship between individual soil hydraulic properties and the reference soil.
The governor equation is solved using Galerkin's linear finite element method applied to the triangular element network. The saturated and unsaturated states are implemented by finite difference format integration. The result equation is solved in an iterative manner, by linearization and subsequent Gaussian elimination method for the banded matrix, the symmetric matrix conjugate gradient method or the asymmetric matrix orthogonal minimization method. Additional measures to improve the efficiency of solving transient problems, including automatic time step adjustments and ensuring that Courant and Peclet numbers do not exceed preset levels. The water conservation method was evaluated using the mass conservation method proposed by Celia et al., 1990. Decreasing the numerical oscillation ascending weight is included as an option to solve the migration equation.
In addition, HYDRUS can perform Marquardt-Levenberg type parameter estimation techniques for hydraulic inverse or solute transport of selected soils and to measure transient or steady-state flow and migration data (only in 2D versions). This process allows estimation of several unknown parameters such as observed water content, head, concentration, or instantaneous or cumulative boundary flux (eg, infiltration or outflow data). Additional retention or hydraulic conductivity data and constrained optimization of the parameter compensation function, the parameters of the constrained optimization remain in the feasible domain (Bayesian estimation) and can be included in the parameter estimation process.
A new module simulates the biochemical conversion and degradation process of groundwater flow constructed wetlands. This module was developed for the two-dimensional application of HYDRUS (Langergraber and Simunkek, 2005, Langergraberetal, 2009).
This module considers a large number of physical, chemical and biological processes active in wetlands, including three components of biochemical degradation and conversion processes (easy to degrade, slowly biodegradable and inert), tetrazo compounds (ammonium, nitrous acid) Salts, nitrates, and diazo), inorganic phosphorus, heterotrophic and autotrophic microorganisms, dissolved oxygen and/or sulfur, which are both active and interacting.
Additional module
The UNSATCHem module is primarily used to simulate migration and reaction of major ions. The UNSATCHEM module simulates the migration of major ions (such as calcium, magnesium, sodium, potassium, SO4, carbonic acid, and Cl) in a saturated saturated porous medium, including major ion equilibrium and non-equilibrium chemical reaction kinetics. The generated code can be used to predict the major ion chemistry, water, and solute fluxes of the soil in transient flows.
The Wetlands module is used to simulate artificial wetland reactions. The design of the constructed wetland water treatment system optimizes the processes found in the natural environment. The HYDRUS Wetland module includes two biokinetic model formulas. In the original wetland CW2D module, the conversion and degradation processes of aerobic and anoxic processes of organic matter, nitrogen and phosphorus, and the organic matter, oxygen and sulfur in the aerobic, anoxic and anaerobic processes of the new CWM1 module are considered. .
The DualPerm module (version 2.02 and above) is used to simulate two-dimensional variable saturated water motion and solute transport in dual-permeability porous media, ie preferential and non-equilibrium moisture and solute transport.
The C-Ride module (version 2.02 and above) is used to simulate the solute transport of two-dimensional colloids that frequently occur to strongly adsorb contaminants (eg heavy metals, radionuclides, pharmaceuticals, pesticides, explosives), mainly associated with solids. They are generally considered to be stationary, but they can also adsorb moving colloidal particles (such as microorganisms, humic substances, suspended clay particles and metal oxides), which can act as a carrier for contaminants, thus providing a rapid Migration route.
The HP2 module (version 2.02 and above) combines HYDRUS (the two-dimensional part) with the PHREEQC geochemical code [Parkhurst and Appelo 1999] to develop this new comprehensive simulation tool (HP2—HYDRUS-PHREEQC-2D abbreviation), mainly Different from a similar one-dimensional module HP1. This module can consider a variety of mixed balance/dynamic biogeochemical reactions.
HYPAR is a parallel version of the standard 2D and 3D HYDRUS calculation modules. (h2d_calc.exe and h3d_calc.exe)
HYPAR uses parallel computing tools and techniques to effectively take advantage of multi-core and multi-processor computers and significantly accelerate time-consuming simulations, especially those that require large amounts of finite elements
The purpose of the Slope Classic add-on module is mainly for the stability check of dikes, dams, cutting the earth and fixing the baffle structure. The effect of water modeling uses the distribution of pore pressure, which is the result of the automatic importation of the time from the water snake. The water distribution for each time step can be analyzed separately.
The SLOPE Cube (Slope Stress and Stability) accessory module was developed in collaboration with Dr. Ning Lu of the Colorado School of Mines. It uses a uniform effective stress method for both saturated and unsaturated conditions. The purpose of this module is to predict infiltration-induced landslide initiation and to carry out slope stability analysis under variably-saturated soil conditions.
GUI
An output requirement for running HYDRUS based on Microsoft Windows graphical user interface (GUI) management, as well as grid design and editing, parameter configuration, problem execution, and result visualization. HYDRUS also includes a set of controls that allow the user to create a stream and migration model and analyze the running graphics. Use space and cross section views and line graphs to check inputs and outputs. The main program unit of the HYDRUS graphical user interface defines the overall computing environment of the system. This main module controls the execution of the program and determines which other optional tools are necessary. The module also contains a project manager and two pre- and post-processing units. The pre-processing unit includes all necessary parameter specifications, such as the successful running of the HYDRUSFORTRAN language code, the relatively simple grid generator for rectangular and hexahedral transport domains, and the complex 2D and 3D domain mesh for unstructured finite element meshes. The generator, the soil hydraulic properties of a small catalog, and the soil hydraulic properties generated from the RosettaLite program of soil structure data.
Automatic generation of finite element mesh
Data preprocessing involves a two-dimensional flow region specification with continuous creases, arcs, spline functions, discretization of domain boundaries, and the next version of an unstructured finite element mesh. HYDRUS (Standard Edition) comes with an optional mesh generator, and Meshgen can generate a 2D domain of an unstructured finite element mesh. Based on Delaunay's inference, HYDRUS has been seamlessly integrated into the HYDRUS environment. In the absence of a Meshgen program, HYDRUSGUI provides an automatic build option for a simple, structured grid (Lite version). The 3D version adds the specified number of layers of the same or different thickness under the Lite and Standard versions. HYDRUS3D Professional has a 3D mesh generator (GENEX and T3D) that generates an unstructured finite element mesh for a generic 3D domain.
Post processing
The output graph includes a 2D contour (contour or color spectrum) of water content, flow rate, concentration, temperature in space or cross-sectional view. The graphical output also includes velocity vectors, colored edges, points of color, graphical displays and animations of successive time steps, and selected boundary or internal section lines. The user can zoom in on the area of ​​interest and the vertical scale of the cross-sectional view can also be enlarged. The grid can also display borders and numbered triangles, edges, and points. Watchpoints can be added anywhere in the grid. Views of grid and/or spatial distribution results (pressure head, water content, velocity, concentration, and temperature) all use high resolution color or grayscale values. The interface also includes an extensive online help menu.
Domain and finite element mesh area
To simplify the work of complex migration geometry, these graphics can be divided into simple parts called Sections. Only these simple parts can be displayed in the view window, while the rest are hidden. There are two types of Sections: geometric object based and finite element mesh based. Multiple sections can be displayed at the same time. Unwanted parts of the transport area can be cut and hidden using various commands.
Latest system requirements
Operating system: WindowsXP/WindowsVista (32or64bit)/Windows7 (32or64bit)/Windows8 (32or64bit)
2GHz X86 CPU
2MBRAM
10GB of hard disk space, at least 500MB of installation space
Resolution 1024x768 pixels
Recommended system configuration
Using the model of HYDRUS3D, the recommended system configuration is:
Operating system Windows7 (32-bit or 64-bit)
Multicore CPUs of 3GHz or higher
4GBRAM (8GB for 64-bit system)
500GB hard drive space
The graphics card is accelerated by OpenGL hard disk with a resolution of 1600x1200
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