This tutorial considers water flow and solute transport in a simple three-dimensional transport domain. The transport domain is a relatively simple hexahedral domain with a slope in the X-direction. Dimensions of the transport domain are 1000 * 250 * 200cm and there is a groundwater 100 cm below the soil surface. There is a source of water and contaminant at the soil surface. The problem is divided into two parts. In the first part, the geometry of the transport domain and its discretization is defined and initial and boundary conditions are specified. In the second part, final pressure head profile from the first run is imported as an initial condition, and pulse of solute is added into the surface source. The example thus again demonstrates how results of a previous simulation can be used in follow-up calculations with different boundary conditions or having additional features. Users will learn how to define a simple threedimensional transport domain and how to use Sections when defining initial and boundary conditions. Users will also learn various ways of viewing transport domain and simulation results.
本教程认为在一个简单立体交通领域的水流，传送域是一个在X方向有斜角的相对简单的六面体，传送域的尺寸是1000* 250 *200厘米，100厘米以下的土壤表面有一个地下水。问题被分
为两个部分，在第一个方面，传送域及其离散化的几何形状被确定，初始条件和边界条件被指定。 这样的例子再次证明了先前模拟的结果如何被应用于后续计算不同的边界条件，或具有其他的附加功能。用户将学习如何定义一个简单的三维传输域，以及如何使用章节定义初始条件和边界条件。用户也将学习各种方式查看运输域和仿真结果。
时间信息
Time Units | Time units [T] to be used throughout the application (days, hours, min, sec). When units are changed during or after data entry, then all input variables are converted automatically into the new units. 时间单位可以在整个应用程序中使用（天，小时，分钟等等）。当在数据输入以后时间单位改变，那么所有输入的将自动转化为新的时间单位。 |
Initial Time | Starting time [T] of the calculation. 计算起始时间。 |
Final Time | Final time [T] of the calculation. 计算最终时间。 |
Initial Time Step | Initial time increment, dt [T]. The initial time step should be a function of the type of problem being solved. Problems with high pressure gradients (e.g., infiltration into an initially dry soil) and for soils with highly nonlinear soil hydraulic properties require relatively small initial time steps. The initial time step is used at the beginning of the simulation or whenever boundary conditions are substantially changed (e.g., the water flux changes by 25% or more). 初始时间增量。初始时间步长应该是一个解决问题的功能。高压力梯度问题（例如渗入干燥的土壤）和具有高度非线性的土壤水力特性需要相对小的初始时间步长。初始时间步长在模拟开始或者边界条件具有实质上的改变的时候被应用。（例如水流量改变了25%或者更多）。 |
Minimum Time Step | Minimum permitted value of the time increment, dtmin [T]. The minimum time step must be smaller than a) the initial time step, b) interval between print times, and c) interval between time-variable boundary condition records. 时间增量的最小允许值。最小时间步长必须比以下条件更小：a）初始时间步长，b）输出时间间隔，c）随时间变化的边界条件记录间隔。 |
Maximum Time Step | Maximum permitted value of the time increment, dtmax [T]. The maximum time step can be a relatively large number (the optimal time step is selected by the program), unless small time steps are required, for example, to simulate temperatures during one day. 时间增量的最大允许值。最大时间步长可以是一个比较大的数（最佳时间步长由程序选定），除非要求较小的时间步长，例如，模拟一天的温度。 |
边界条件
Time-Variable Boundary Condition - The number of time-dependent boundary records and time-dependent boundary conditions must be specified when this box is checked. The boundary conditions otherwise are assumed to be constant in time. The GUI can handle only a limited number of time variable data records (around 15,000; depending on the problem). If a required number of data records is larger than this number, a user needs to extend the ATMOSPH.in file manually using the following procedure.
随时间变化的边界条件——选中此框后，随时间的边界条件记录和随时间变化的边界条件的数量必须被指定。否则最后边界条件被假设为常数。GUI只能处理有限数量的时间变量的数据记录（大概15000左右）。如果需要的数据记录数比这个数据更大，用户需要手动使用下列程序扩展ATMOSPH.in程序。
In the Print Options part of the dialog window, one decides whether certain information concerning mean pressure heads and concentrations, mean water and solute fluxes, cumulative water and solute fluxes, and time and iteration information is printed at each tim
e step (T-Level Information), after n time steps (Every n time steps), at a certain defined time interval (Interval Output), or if the information is sent to the screen during the calculations (Screen Output). When the simulation ends users are by default asked to hit the Enter key of the keyboard to return to the GUI from the computational window. This action can be disabled by unchecking the Hit Enter at the End check box.
在对话框的输出选项对话框，需要决定相关信息是否影响压力水头和浓度均值，水和溶质通量均值，累积的水和溶质通量
T-Level Information | This check box decides whether certain information concerning mean pressure heads and concentrations, mean water and solute fluxes, cumulative water and solute fluxes, and time and iteration information, are to be printed at each time step, after n time steps, or only at preselected times (Print Times) or Time Intervals. |
Interval Output | Users can specify whether or not information concerning mean pressure heads and concentrations, mean water and solute fluxes, cumulative water and solute fluxes, and time and iteration information is to be printed at a regular Time Interval. |
Screen Output | Check box to decide whether or not information about the simulation run is to be printed to the screen during execution of the HYDRUS computational code. We recommend to check this box for direct problems, but not for inverse problems. |
Print Times | In the Print Times part of the dialog window one specifies the number of Print Times (Count) at which detailed information about the pressure heads, water contents, concentrations, temperatures, fluxes, and the soil water and solute balances will be printed. Clicking on the Default command button will cause the print times to be distributed evenly between the initial and final time. 在对话框的PT部分，在压力水头、水容量、浓度、温度、通量的细节信息里，指定输出时间的数量，土壤睡和固体的平衡将会被输出。点击默认按钮将会导致输出时间在初始和最终时间内被平衡分配。 |
Variable | Description |
Time | Time for which a data record is provided [T]. Boundary condition values are specified for the time interval preceding time given at the same line. Thus BC values specified in the first row are for the time interval between the initial time and time specified on the same line. 提供的一个数据记录。边界值在之前的时间间隔给出时在同一行指定。因此，BC值在第一行指定，最初的时间和时间间隔在同一行指定。 |
Precip | Precipitation [LT-1] (in absolute value) (applied to the atmospheric boundary). 降水量（绝对值）（应用于大气边界层） |
Evap | Potential evaporation rate [LT-1] (in absolute value) (applied to the atmospheric boundary). 潜在蒸发率（绝对值）（应用于大气边界层） |
Trans | Potential transpiration rate [LT-1] (in absolute value). 潜在蒸腾率（绝对值） |
hCritA | Absolute value of the minimum allowed pressure head at the soil surface [L] (applied to the atmospheric boundary). 土壤表面允许的水头最小绝对值（应用于大气边界层） |
Var.Fl1 | Drainage flux [LT-1] across the bottom boundary, or other time-dependent prescribed flux boundary condition (positive when water leaves the flow region); set to zero when no time-dependent flux boundary condition is specified. Ditto for Var.Fl2, Var.Fl3, or Var.Fl4. 底部边界的排水量，或者其它随时间变化的恒定流量边界条件（水离开流域时活跃）；当边界条件被指定为没有随时间变化的流量时，设为0。 |
Var.H-1 | Groundwater level [L] (usually negative), or other time-dependent prescribed head boundary condition; set equal to zero when no time-dependent head boundary condition is specified. Ditto for Var.H-2, Var.H-3, or Var.H-4. 地下水水平（通常为负），或者其它随时间变化的恒定水头边界条件，当没有随时间变化的水头边界被指定时，均设为0。Var.H-2, Var.H-3, or Var.H-4相同。 |
Temp1 | The first time-dependent temperature [K] that can be used for nodes with time variable boundary conditions (atmospheric BC, variable head/flux BC) (is not specified if heat transport or time variable boundary conditions are not considered). 最初随时间变化的温度，可以被用作随时间变化的边界条件的节点（大气BC，变化水头/流量BC）（如果热传输或者随时间变化的边界不考虑时不指定） |
Temp2 | The second time-dependent temperature [K] that can be used for nodes with time variable boundary conditions (is not specified if heat transport or time variable boundary conditions are not considered). 第二随时间变化的温度，可以被用作随时间变化的边界条件的节点（如果热传输或者随时间变化的边界不考虑时不指定） |
Conc1 | The first time-dependent solute concentration [ML-3] that can be used for nodes with prescribed time variable boundary conditions (atmospheric BC, variable head/flux BC) (not specified if solute transport is not considered). 最初随时间变化的溶质浓度，可以被用作随时间变化的边界条件的节点（大气BC，变化水头/流量BC）（如果固体传输不考虑时不指定） |
Conc2 | The second time-dependent solute concentration [ML-3] that can be used for nodes with prescribed time variable boundary conditions (atmospheric BC, variable head/flux BC) (not specified if solute transport is not considered). 第二随时间变化的溶质浓度，可以被用作随时间变化的边界条件的节点（大气BC，变化水头/流量BC）（如果固体传输不考虑时不指定） |
Conc3 | The third time-dependent solute concentration [ML-3] that can be used for nodes with prescribed time variable boundary conditions (atmospheric BC, variable head/flux BC) (not specified if solute transport is not considered). 第三随时间变化的溶质浓度，可以被用作随时间变化的边界条件的节点（大气BC，变化水头/流量BC）（如果固体传输不考虑时不指定） |
The last three entries are entered for each solute.
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