SMS:ADCIRC Weirs and Island Barriers

ADCIRC Weirs and Island Barriers

An ADCIRC weir is a boundary type that are assigned to two nodestrings on an ADCIRC mesh. A weir comprises of two nodestrings next to each other with an equal amount of nodes on each nodestrings. In order to add a weir in ADCIRC, there must be two adjacent nodestrings available as shown in figures 1 and 2 below.

Figure 1 – Parallel nodestrings that can be made into weirs.

Figure 2 – Adjacent nodestrings that can be assigned as weir.

The number of nodes on each nodestrings must be of an equal amount or a weir cannot be assigned. See figure 3 below. Each node and it's corresponding node on the parallel nodestring will form a node pair.

Figure 3 – Nodestrings with same number of nodes.

Weir Options

Once two nodestrings with same number of nodes exist, they can be assigned as a weir by selecting both weirs and selecting Assign BC. The Nodesting attributes will open. By selecting Weir and then clicking on Parameters button, the Weir Options dialog will open. The dialog shows the different Node pairs and elevation for each node pair.

Figure 4 – Weir Options dialog.

Elevation

Elevation of each node pair. The elevation for each node pair can be entered manually or can be interpolated from a dataset

Super

Weir flow coefficients for super critical flow. A typical value for this is 1.0.

Sub

Weir flow coefficients for sub critical flow. A typical value for this is 1.0.

• Pipe
• Elevation = elevation of the pipe
• Diameter = diameter of pipe

• Coefficient = f (L/D)

File:ADCIRCweir6.jpg where

– L is the length of the pipe

– D is the hydraulic diameter of the pipe (for a pipe of circular section, this equals to the internal diameter of the pipe)

– f is a dimensionless coefficient called the Darcy friction factor. It can be found from a Moody diagram or by solving the Colebrook equation.

Interpolate Elevations Button Clicking on the Interpolate Elevations button opens the XY Series Editor. The XY Series Editor can be used to generate and edit curves defined by a list of x and y coordinates. The curve can be created and edited by directly editing the xy coordinates using a spreadsheet list of the coordinates. An entire list of curves can be generated and edited with the Editor and curves can be imported from and exported to text files for future use. You can also paste your xy data directly to the spreadsheet.

Extract Elevations

Data entered in as weir or island barrier boundary condition data can be used to create arcs and/or set grid cell elevations. SMS calculates the midpoint between the two nodestrings used to create a weir or island barrier boundary condition. At each of these midpoints, the boundary condition elevation is used. To use this functionality, select the Extract Weir Elevations... option from the Nodestring menu. This will open the Extract Weir Elevations dialog. Here you can choose to use only selected nodestrings or all nodestrings in the mesh. If a coverage is used, SMS will create arcs that represent the weirs on the specified coverage. If one or more grids are used, SMS will set the elevation values for all grid cells that lie underneath the weirs or island barriers by interpolation.