CMS-Flow Boundary Conditions

Boundary Conditions

CMS-Flow Boundary Conditions window

CMS-Flow has five types of boundary conditions which are listed and discussed below. The figure below shows the CMS-Flow Boundary Conditions window in SMS. All CMS-Flow boundary conditions are forced at the edges of the domain by use of cellstrings defined with the Surfacewater Modeling System (SMS). Cellstrings can either be created manually or using the SMS tool called Generate Along Boundary which is found under the Cellstring menu.

Land

The land boundary conditions is equivalent to a zero flux boundary condition. The land boundary condition is the default boundary condition when a cell string is created. It is not necessary to define land boundaries in the interior of the CMS-Flor domain, since land boundarys will automatically be detected by CMS-Flow based on the local water depths and the presence of inactive land cells.

Flow Rate-Forcing

The flow rate boundary condition specifies a time series of water fluxes in units of m^3/s per cell.

NOTES:

• Total flow rate specified is divided between the total number of cells in the cellstring with each carrying a portion of the total.
• This boundary type may only be specified along cell strings which are straight.
• The sign of the flow rate curve is dependent on the direction of flow with respect to the origin (always lower-left hand corner of the grid).

This guide should assist in proper assignment:

• • Flow rate from the East - Negative value
  • Flow rate from the West - Positive value
  • Flow rate from the North - Negative value
  • Flow rate from the South - Positive value

Water Surface Elevation Forcing

Two types of Water Surface Elevation Forcing exist for CMS-Flow. Once a water surface elevation curve (or series of curves) is applied, the user is able to display the curve information graphically.

1. Define curve (single time series curve for each cell string)

User creates a cellstring for the given boundary and defines a time series curve. The value for each time on this curve is applied to all cells along the designated cellstring. The time series curve may be specified by either importing an SMS *.xys file, copying tabular data into SMS, or manually entered the time series information in SMS.

2. Extract from data set (time series curve for each cell on cell string)

User creates a cellstring for the given boundary and extracts multiple time series curves from a dataset or database. Each cell along the cellstring is given its own time-series curve information. Examples are:

• Extraction of water surface elevation values from a larger domain solution (ie. Larger CMS-Flow or ADCIRC grid)
• Extraction of tidal constituent information from a tidal database, from which a water surface elevation curve can be generated.

Tidal Constituent Forcing

Tidal Constituent Forcing window in SMS

CMS-Flow as the option of forcing with a harmonic tidal water surface elevation. To assign a boundary as a tidal boundary:

1. Select a cellstring
2. Click under CMS-Flow | Assign BC...
3. In the CMS-Flow Boundary Conditions window, click on Tidal constituent-forcing, and click OK.
4. Open the CMS-Flow Model Control window and click on the tab labeled Tidal.
5. Enter the amplitudes and phases of the tidal constituents. Note that the same amplitude and phase are applied to entire cellstring and click OK

Tidal constituents used in CMS

Constituent	Speed	Constituent	Speed	Constituent	Speed	Constituent	Speed
SA*	0.041067	SSA*	0.082137	MM*	0.54438	MSF*	1.0159
MF*	1.098	2Q1*	12.8543	Q1*	13.3987	RHO1*	13.4715
O1*	13.943	M1*	14.4967	P1*	14.9589	S1*	15.0
K1*	15.0411	J1*	15.5854	OO1*	16.1391	2N2*	27.8954
MU2*	27.9682	N2*	28.4397	NU2*	28.5126	M2	28.9841
LDA2*	29.4556	L2*	29.5285	T2*	29.9589	S2	30
R2*	30.0411	K2	30.0821	2SM2*	31.0159	2MK3*	42.9271
M3*	43.4762	MK3*	44.0252	MN4*	57.4238	M4	57.9682
MS4*	58.9841	S4*	60.0	M6	86.9523	S6*	90.0
M8*	115.9364

* Only available through advanced cards for CMS >v4.0

Water Surface Elevation and Velocity Forcing

Users are able to extract both water surface elevations and velocity components from a larger domain solution (ie. Larger CMS-Flow or ADCIRC grid).

Salinity Concentration Forcing

If salinity transport is active for the simulation, the user has the ability to use existing hydrodynamic cellstrings in the interface in order to provide a time-series curve of salinity concentrations. The salinity concentrations must be provided in units of ppt.