SMS:ADH Model Control Time

Time tab of the ADH Model Control dialog

The ADH time parameters are accessed in the ADH Model Control window by clicking on the Time tab.

ADH is set up as a transient conditions model, however, a steady state simulation can be invoked which utilizes an iterative process to converge to a solution. A steady state solution is accepted if the end time of the model is reached or the iteration tolerance requirement (see Model Parameters ) is met. It's required to ensure that all series data are acceptable (constant linear series) if the steady state method is used. ADH also includes a quasi-unsteady method which strings multiple steady state simulation together to form a step function style hydrograph.

Due to the nature of a steady state simulation, constituent transport and bed layers cannot be included in the simulation. If any constituent (and bed layer) is specified in a dynamic simulation and then the simulation is changed to steady state, SMS will clear the constituent data (and bed layer specification). A message will warn of this effect when the steady state simulation type is selected and constituent data (and a bed layer) exists. Another message will state that SMS has cleared the data (if steady state is still selected) when switching to another tab or exiting Model Control by selecting OK.

Since series data specified for a dynamic simulation is usually inappropriate for a steady state simulation, a change in simulation type from dynamic to steady state will force SMS to clear all previously specified series data when changes are accepted in Model Control. This data is usually associated with the boundary conditions of materials, nodes, and nodestrings. A message will warn of this effect when the simulation type is changed and series data exists. Another message will state that SMS has cleared the data (if the simulation type remains changed) upon accepting the changes (exiting Model Control).

The following controls specify the timing parameters for the ADH model run.

Simulation

Dynamic / Steady state / Quasi-unsteady radio group specifies the simulation type.

• Dynamic option provides the following:
  • Start date and time field and the Delay model start check box with positive real number and units combo box correlates to the TC T0 card.
  • End date and time field (with the defined start) specifies the simulation run length on the TC TF card.
  • Duration positive real number edit field and units combo box also specifies the simulation run length. This field and the End field will update as the other is changed.
• Steady state option provides the following:
  • Duration positive real number edit field and units combo box to specify the simulation length.
• Quasi-unsteady option is currently unavailable.

Apply adaptive time control check box includes the TC IAC card or TC NDP card when checked or unchecked, respectively.

Time Step Control

Time step size curve button with the associated Series time units combo box, and Specify curve fit tolerance check box and positive integer edit field defines the data to be associated with the TC IDT card and its XY1 series definition card. Clicking on the curve button will open the XY Series Editor. This series must be defined for the entire model run length, so include or exceed the time Model run time listed in the Simulation group. This control group is available only when the Dynamic simulation type is selected.

Initial time step positive real number edit field and units combo box specifies the time step value of the TC STD card. This control group is available only when the Steady state simulation type is selected.

Specify extra sediment transport time steps check box and positive integer edit field while include the TC SDI card when checked. If sediment transport is included in the simulation and this control is not checked, then the model will calculate sediment according to the time increment specified by the Time step size series.

Dynamic simulation type option, in the simulation group, provides the following:

• Time step size curve button selects the time series data to be associated with the TC IDT card. Clicking on the curve button will open the Time Series editor (limited to the time step Size curve group). The selected series should be defined for the entire model run length, so include or exceed the time model run time listed in the Simulation group.
• SNumber of sediment transport time steps per hydrodynamic time step positive non-zero integer edit field correlates to the TC SDI card. This field is only enabled if sediments have been specified on the Transport Constituents tab of model control. This applies only to sediments and not any other constituents. If sediment transport is not included in the simulation, then the TC SDI card is not included in the file.
• Max sediment time steps value is associated with the TC SDI card. This allows specifying smaller sediment transport time steps that what is used for the hydrodynamic time step. Sediment constituents must exists otherwise this option will be grayed out and the card will not be written.
• Automatic time step option, provides the following:
• Specifies the time step data for the TC ATF card. Pressing the Calculate button calculates the time step based on the formula:

${\frac {x}{\sqrt {g*h}}}$

Where:

x = mesh element length (currently the distance between the 1st and 2nd node in the 1st element)

g = gravitational acceleration

h = minimum water depth

If an initial dataset doesn't exist, the automatic time step option is disabled and the TC ATF card is not written.

Steady State simulation type option, in the simulation group, provides the following:

• Initial time step positive real number edit field and units combo box specifies the time step value of the TC STD card. This control group is available only when the steady state simulation type is selected.

Related Topics

• ADH Model Control