CMS-Flow Model Parameters

Figure 1. CMS-Flow Model Control : Model Parameters tab in SMS 13.2.12.

All of the CMS-Flow model parameters, settings, and output options are controlled from the CMS-Flow Model Control window (Figure 1). The window has several tabs including the Flow tab in which most of the general settings are set for CMS-Flow. To open the CMS-Flow Model Control window, click on CMS-Flow | Model Control. The first tab will be the Flow tab. There are several sections within the tab including Time Control and Hot Start options.

General

Figure 2: Time Control parameters for the simulation

Time Control

Below are some of the CMS cards related to the Time Control of the Flow tab. Table 1 provides a brief description of the CMS cards used for time control.

Card	Arguments	Default	Range	Description
STARTING_JDATE	REAL	none	none	Julian data in YYDDD with YY being last two digits of the year, and DDD the Julian day of the year.
STARTING_JDATE_HOUR	REAL	none	none	Julian hour .
HYDRO_TIME_STEP	REAL	Calculated based on solution scheme and courant number	none	Sets to the time step for hydrodynamics in seconds.
DURATION_RUN	REAL	48.0	>RAMP>0	Sets the duration of the model simulation in hours.
DURATION_RAMP	REAL	1.0	Sets the length of the ramp period in which the model forcing is slowly ramped from zero.

Hot Start

Figure 3: Hot start parameters on CMS-Flow Model Control

The term Hot start refers to starting a simulation with an initial condition other zero (cold start). Hot starts are used for specifying initial conditions or restarting simulations at intermediate times. The hot start controls are set in the Flow tab of the CMS-Flow Model Control window.

Hot Start File

Figure 4. HDFView showing the structure of the CMS Hot Start File.

The CMS hot start feature CMS lets the user restart simulations that have been stopped due to electric outages, hardware malfunctions, or model crashes. In the case of a model crash the user, may restart the model using larger solver iterations and/or time steps to stabilize the simulation. The user has the option to specify a hot start output time or an interval for outputting a recurring hot start file. Every time the hot start file is written, it overwrites the previous information. The CMS Hot Start file saves information on the water elevation (pressure), and current velocities. If the sediment transport is active, then the water depth and sediment concentrations are also saved for each size class. Only the very last record of information is preserved (no starting from earlier intervals).

The CMS hot start files are written as binary XMDF files by default. Depending on the type of hot start (single file or recurring), the names are as follows are saved in the directory of the CMS-Flow files:

• SingleHotStart.h5
• AutoHotStart.h5

After saving a CMS Hot Start file, it is a good idea to rename the file with a different name before using it as an initial conditions file. This way, the file will not be overwritten in future simulations.

Table 1. Hot Start CMS-Flow Cards

Card	Arguments	Default	Range	Description
HOT_START_TIME	REAL	none	none	Single time after start at which to output a single hot start file.
AUTO_HOT_START_INTERVAL	REAL	none	none	Sets the recurring hot start output interval .

• Initial conditions file
• Write Hot Start output file
• Automatic recurring Hot Start file

Solution Scheme

This refers to the temporal discretization of the hydrodynamic, sediment and salinity transport equations. There are two options in CMS:

• Implicit - First order backward Euler scheme. Uses a time step on the order of 5-15 minutes. Appropriate for cases which can be simulated with large computational time steps such as long term morphology change at inlets.
• Explicit - First order forward Euler scheme. Uses a time step on the order of 0.5-1.0 second. Appropriate for cases that vary quickly in time such as flooding or barrier island breaching.

Matrix Solver

Users have a matrix solver:

• Gauss-Seidel
• Gauss-Seidel-SOR
• BicGSTab
• GMRES

Card	Arguments	Default	Range	Description
SOLUTION_SCHEME	CHARACTER	EXPLICIT	EXPLICIT | IMPLICIT	Determines the solution scheme used in CMS-Flow.

Threads

• Number of threads

Salinity/Temperature

The general parameters are the water density and temperature. The CMS-Flow cards for the general parameters are described in the table below.

Table 1. CMS-Flow cards related to the general parameters

Card	Arguments	Default	Description
WATER_DENSITY	REAL	1025	Water density in kg/m^3.
WATER_TEMPERATURE	REAL	15	Water temperature in degrees Celcius.

Output

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