User Guide 007

The extracted water levels are stored in the CMS-Flow Model Parameters file. Below is an example of how the CMS-Flow card for the extracted wa-ter level times boundary.

example 2-33

Step-by-Step Instructions: Extracted WSE from a Regional Model To assign this type of BC in SMS: 1. If not already done, load a CMS-Flow grid in SMS.

figure 2-54

2. If not already done, load in a larger-domain (regional) simulation files including the water level solution (typically either an CMS or ADCIRC simulation).

figure 2-55

3. If not already created by SMS, create the CMS-Flow cellstring at the boundary (see section Creating and Deleting Cell Strings in SMS for details). 4. Select the CMS-Flow cellstring (see section Selecting a Cellstring for details). 5. Open the CMS-Flow Boundary Conditions Window (see section Assigning a Boundary Condition for details). See figure below.

figure 2-56

6. Select WSE-forcing in the Boundary Conditions section on the left side of the window. 7. Select Extract from dataset in the Options section on the right side of the window. 8. Click on From Regional Model. The Extract Boundary Conditions window will appear (see example figure below). 9. Select the water level forcing dataset and the start and end times for the extraction. 10. Select the Extract button in the Extract Boundary Conditions win-dow. The window will close.

figure 2-57 11. In the CMS-Flow Boundary Conditions window, select the OK but-ton. 12. Save the SMS project File (*.sms) or CMS-Flow Simulation File (*.cmcards).

Notes: • Due to their size, the tidal databases do come installed with SMS, and must be downloaded separately. Before using the tidal databases in SMS for the first time it is necessary to follow the steps below. • If an ADCIRC simulation is used to extract water levels, make sure the ADCIRC grid is in the same horizontal projection as the CMS-Flow grid.

Step-by-Step Instructions: Extracted WSE using Tidal Constituents To assign an extracted water surface elevation boundary using tidal con-stituents from a tidal database: 1. If not already done, load a CMS-Flow grid in SMS. 2. If not already created by SMS, create the CMS-Flow cellstring at the boundary (see section Creating and Deleting Cell Strings in SMS for details). 3. Select the CMS-Flow cellstring (see section Selecting a Cellstring for details). 4. Open the CMS-Flow Boundary Conditions Window (see section Assigning a Boundary Condition for details). See figure below.

figure 2-58

5. Select WSE-forcing in the Boundary Conditions section on the left side of the window. 6. Select Extract from dataset in the Options section on the right side of the window. 7. Click on using Tidal Constituents. The Extract Boundary Condi-tions window will appear (see example figure below). 8. Select the water level forcing dataset and the start and end times for the extraction. 9. Select the Extract button in the Extract Boundary Conditions win-dow. The window will close.

figure 2-59

10. In the CMS-Flow Boundary Conditions window, select the OK but-ton. 11. Save the SMS project File (*.sms) or CMS-Flow Simulation File (*.cmcards).

Extracted Water Level and Velocity Time Series Boundary The water level and velocity at a boundary can be specified as: 1. Cell-specific time-series curves (i.e. one time-series for each boundary cell). This boundary type is used when extracting boundary conditions in SMS. 2. Interpolated values from a parent grid simulation (nesting). 3. Cell-specific cosine series using interpolated tidal constituents from a tidal database.

example 2-34

Cross-shore Boundary Condition In the implicit flow solver, a cross-shore boundary condition is applied by solving the 1-D cross-shore momentum equation including wave and wind forcing (Wu et al. 2011a, 2011b). Along a cross-shore boundary, it is assumed that a well-developed longshore current exists. Thus, the along-shore (y-direction) momentum equation can be reduced to (2 16) where , , and are the surface, wave, and bottom stresses in the long-shore direction, respectively. The equation above is solved iteratively for the longshore current velocity. The cross-shore (x) component of the velocity is assigned a zero-gradient boundary condition. The water level due to waves and wind at the cross-shore boundary can be determined by assuming a zero alongshore gradient of flow velocity and negligible cross-shore current velocity. For this case, the cross-shore momentum equation reduces to (2 17)

where and are the wind and wave stresses in the cross-shore direction.