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FESWMS Model Control

(2012-09-27 19:12:45)
标签:

杂谈

分类: SMS

The FESWMS model control dialog is used to set general simulation options. This document highlights the more commonly used options. Refer to the FESWMS manual[1] for a more detailed description of how these parameters affect the model results.

General Tab

The controls in the general tab include model description, FESWMS version, run controls, input options, and output options.

  • Network stamp and BC descriptor

These are comments that are added at the top of the FESWMS input files. The network file (.net) includes only the network stamp but the bc file includes both the network stamp and the bc descriptor.

  • Slip conditions

This controls how boundaries are handled by FESWMS. Slip boundaries allows water to move freely along the boundary. No slip fixes the velocity at fixed boundaries to 0.0. Semi-slip allows water to move along boundaries but reduces the velocities.

  • Run Type

A simulation can compute hydrodynamics, sediment, or both hydrodynamics and sediment (semi-coupled). It is not recommended to use the sediment only option. Use the semi-coupled option instead.

  • Solution Type

This controls whether the simulation will be treated as steady state or dynamic (time dependent). A steady state run requires boundary conditions that do not change and computes a solution that does not change through time.

  • Input Options

This controls the files that will be used in FESWMS. An INI (initial conditions) file is used to provide an initial solution for FESWMS. The initial conditions file format is identical to the FESWMS solution file format and a FESWMS solution may be used for an initial conditions file. Initial conditions files can also be created from inside of SMS. INI files are used as hot starts in the spin down process.

  • Output Options

The scalar data set file and vector data set files are additional output files written in the EMRL dataset format. Regardless of whether this file is used or not, the datasets water surface elevation, depth, and velocities are written to the .flo solution file. The dataset files will have the same base name as the other project files and have the extensions scl (scalar) and vec (vector). The data written to the data set file can be specified by clicking on the options button. Available scalar data sets include: Depth-averaged velocity magnitude, Unit flow rate magnitude, Froude number, Mechanical energy head elevation, Bed shear stress magnitude, Vorticity magnitude, Wind Speed, Depth of general scour, Scoured bed elevation, Sediment concentration, Sediment volumetric transport rate, Sediment volumetric transport capacity, and Sediment transport rate deficit. Available vector data sets include: Depth-averaged flow velocities, Unit flow rate, Bed shear stress, Tropical cyclone wind velocities, Sediment volumetric transport rates, and Sediment volumetric transport capacities.

Timing Tab (时间单位为小时/hours)

  • Relaxation factor (松弛因子,减小时可使计算稳定但会增加计算时间)

Affects how fast and reliable FESWMS will find a solution. Reducing this value may help FESWMS achieve a solution but may increase runtime.

  • Iterations(迭代次数,算例发现其最大取值为99,调节松弛因子可使单次迭代计算时间增加)

This is the maximum number of iterations to perform. There will be fewer iterations if the model reaches the convergence parameters before reaching this number of iterations (see parameters tab for convergence parameters).

  • Starting time(开始瞬态模拟的时间/hours)

The time to start a dynamic simulation in hours.

  • Run time(模拟长度/hours)

The length of the simulation in hours.

  • Time step size(时间步长)

The length of time for each time step in hours. FESWMS is an implicit model so the time step size is not dependent upon the courant number.(FESWMS为隐式模型,故时间步长不依赖于库朗数)

Parameters Tab

General Parameters

  • Water surface elevation

This is the initial water surface elevation for a cold start simulation. This number should always be larger than the elevation of the highest node in the mesh.

  • Unit flow convergence

The maximum change of unit flow between iterations that will be considered a acceptable for a converged solution.

  • Water depth convergence

The maximum change of water depth between iterations that will be considered acceptable for a converged solution.

  • Storativity depth(控制单元干湿的重要参数,一般在0.5~3 ft之间取值,可使模型计算稳定,特别是存在动边界问题时)

Storativity allows an element to remain active as long as the water surface elevation is above the highest node value minus the storativity depth. Specifying a non-zero storativity value generally increases the stability of the model.

  • Element wetting/drying

Unless this is checked, FESWMS will not allow elements to wet and dry during a simulation.

  • Depth tolerance for drying

Indicates the required depth to rewet a dry node. If this value is zero, any depth above the node will rewet a dry element. Using a value greater than zero helps prevent wet/dry excessive wet/dry oscillations that can lead to instabilities.

Print Tab

This tab controls the information that is written to the printed output file (prt).

Sediment Transport

This tab defines the parameters used for sediment transport including bed configuration.

Wind/Storm Conditions Tab

  • Condition

Wind conditions include none, a directional wind, or a storm (cyclone or hurricane).

  • Wind Parameters

These parameters are used to define the parameters for a directional wind (the same direction magnitude for the entire model domain).

  • Storm Parameters

These parameters are used to define a hurricane or cyclone moving across the model domain. The storm parameters such as direction and central pressure are constant throughout the simulation. The effect of a storm surge combined with the wind fields can be defined using the surge parameters toggle. See the FESWMS manual for a description of the input parameters.

  • Wave Parameters

FESWMS has the ability to consider wave induced stresses. The wave height ratio is the breaking water wave height to depth ratio. Waves will break when the significant wave height equals the water depth times this ratio.

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