ADCIRC Grid and Boundary Information
File (fort.14)
This file is required to run the ADCIRC model.
The basic file structure is
shown below. Each line of input data is represented by a line containing the
input variable name(s) in bold face type. Blank lines are only to enhance
readability. Loops indicate multiple lines of input. Conditional input is
indicated by an if clause following the variable name(s). Definitions of each
variable are provided via hot links.
for k=1 to NP
JN, X(JN), Y(JN), DP(JN)
end k loop
for k=1 to NE
JE, NHY, NM(JE,1),
NM(JE,2), NM(JE,3)
end k loop
for k=1 to NOPE
NVDLL(k), IBTYPEE(k)
for j=1 to NVDLL(k)
NBDV(k,j)
end j loop
end k loop
for k=1 to NBOU
NVELL(k), IBTYPE(k)
for j=1,NVELL(k)
NBVV(k,j) – include this line only
if IBTYPE(k) = 0, 1, 2, 10, 11, 12,
20, 21, 22, 30
NBVV(k,j), BARLANHT(k,j), BARLANCFSP(k,j)
– include this line only if IBTYPE(k)
= 3, 13, 23
NBVV(k,j), IBCONN(k,j), BARINHT(k,j), BARINCFSB(k,j), BARINCFSP(k,j)
– include this line only if IBTYPE(k)
= 4, 24
end j loop
end k loop
General Notes for
All external (external no
normal flow, external with specified normal flow and external barrier)
boundaries should be listed in consecutive order around the outside of the
entire domain before any internal (island with no normal flow or internal
barrier) boundary segments are listed. Internal barrier boundaries that
intersect an external boundary should be specified separately, even though this
will result in some nodes being specified in both boundaries, (see below).
An external no normal flow or
specified normal flow boundary that completely surrounds the domain (e.g., a
lake) should be closed by repeating the first node as the last node.
All no normal flow internal
boundaries (e.g., islands) should be closed by repeating the first node as the
last node.
Unless the boundary segment
is closed, always start listing the boundary nodes where two boundaries
connect.
When an external specified
normal flow or external barrier boundary connects to an external no normal flow
boundary, the initial leg of the external specified normal flow boundary or
external barrier boundary is used to determine the normal and tangential
direction at the node common to both boundaries.
External boundaries with
specified (non-zero) normal flow boundary conditions and external barrier
boundaries can not connect. They must be separated by an external no normal
flow boundary or an elevation specified boundary.
An internal barrier boundary
can intersect an external no normal flow boundary. (For example a levee may
project out of an external no normal flow boundary in which case 2 nodes, the
front and back node on the internal barrier boundary, would be common to the
external boundary.) However, the common external nodes must be treated in the
weak sense. ADCIRC will automatically accommodate this as follows:
-
If the external no flow boundary is specified as essential with slip (IBTYPE(k)=0) and the internal barrier
boundary is specified as essential with slip (IBTYPE(k)=4), the common external
boundary nodes are automatically changed to natural no flow boundary nodes (IBTYPE(k)=20).
-
If the external no flow boundary is specified as essential with no slip (IBTYPE(k)=10) and the internal barrier
boundary is specified as essential with slip (IBTYPE(k)=4), the common external
boundary nodes are automatically changed to natural no flow boundary nodes (IBTYPE(k)=20).
-
If the external no flow boundary is specified as natural with slip (IBTYPE(k)=20) and the internal barrier
boundary is specified as essential with slip (IBTYPE(k)=4), no changes are made.
-
If the external no flow boundary is specified as essential with slip (IBTYPE(k)=0) and the internal barrier
boundary is specified as natural with slip (IBTYPE(k)=24),
no changes are made.
-
If the external no flow boundary is specified as essential with no slip (IBTYPE(k)=10) and the internal barrier
boundary is specified as natural with slip (IBTYPE(k)=24),
the common external boundary nodes are automatically changed to essential no
flow with slip boundary nodes (IBTYPE(k)=0).
-
If the external no flow boundary is specified as natural with slip (IBTYPE(k)=20) and the internal barrier
boundary is specified as natural with slip (IBTYPE(k)=24),
no changes are made.
Internal barrier boundaries
can not intersect external specified flow boundary segments, external barrier
boundary segments or internal no normal flow boundaries.
For all normal flow
boundaries (i.e. IBTYPE(k) = 0,1,2,3,
4,10,11,12,13,20,21,22,23,24,30), the boundary flux integral in the continuity
equation is evaluated with the appropriate (zero, specified or computed) flux.
This is a natural boundary condition. For natural normal flow boundaries (IBTYPE(k) = 20,21,22,23,24), this is the
only lateral boundary condition that is used.
For essential normal flow
boundaries with tangential slip (IBTYPE(k)
= 0,1,2,3,4,10,11,12,13), the normal direction momentum equation (obtained by
re-orienting the x/y momentum equations into normal/tangential directions) is
eliminated and the normal velocity is set by dividing the normal flux per unit
width (zero, specified, or computed) by the total water column height.
For essential normal flow
boundaries with no tangential slip (IBTYPE(k)
= 10,11, 12,13), both momentum equations are eliminated. The tangential
velocity is set equal to zero and the normal velocity is set by dividing the normal
flux per unit width (zero, specified, or computed) by the total water column
height. Use of this boundary condition requires considerable care since
strictly speaking this type of no slip boundary condition is only
mathematically justifiable if lateral viscous terms are used in the simulation
and only physically justifiable if the lateral boundary layers are sufficiently
resolved.
External
Barrier Boundary Note: (IBTYPE(k) =
3, 13, 23)
Outward flow per unit width,
QN2(k,j), normal to and over an external barrier boundary is computed as:
Case
1 – water level below or equal to the barrier height
QN2(k,j) = 0
Case
2 – water level above the barrier height
QN2(k,j) = -(2/3)*BARLANCFSP(k,j)*RBARWL*((2/3)*RBARWL*G)**0.5
where,
RBARWL = ETA1(NBVV(k,j))-BARLANHT(k,j) = water height above the
barrier
ETA1(NBVV(k,j)) = water level computed
at the previous time step at node NBVV(k,j)
This formula is given by
Leendertse (Aspects of SIMSYS2D – A System for Two-Dimensional Flow
Computation, Rand/R-3572-USGS, 1987) and is simply the formula for a broad
crested weir (e.g., see Henderson, Open Channel Flow, section 6.6).
See also General Notes for Normal Flow Boundary Conditions
Internal
Barrier Boundary Note: (IBTYPE(k) =
4, 24)
An
internal barrier boundary consists of a long thin island with parallel front
and back faces. Pairs of nodes are placed on either side of the boundary so as
to provide a one to one correspondence between the nodes on the front face and
back faces. Flow is assumed to go across the boundary from one node to its
paired node on the opposite side. The normal flow is equal in magnitude and
opposite in sign on the two sides of the boundary (e.g., outflow on the front
face = inflow on the back face). Normal flow per unit width, QN2(k,j), at
internal barrier boundary node NBVV(k,j)
and its paired node IBCONN(k,j) is
computed as:
Case
1 – water level below or equal to the barrier height on both sides of the
barrier
QN2(k,j) = 0
Case
2 – water level above the barrier height but equal on both sides of the barrier
QN2(k,j) = 0
Case
3 – water level above the barrier height but greater on the front side than on
the back with subcritical flow across the barrier. Subcritical flow from front
to back across the barrier occurs if the water level height above the barrier
on the back side is greater than 2/3 the water level height above the barrier
on the front side (i.e., RBARWL2 > 0.667*RBARWL1).
QN2(k,j) = -RAMP*BARINCFSB(k,j)*RBARWL2*(2*G*(RBARWL1-RBARWL2))**0.5
Case
4 – water level above the barrier height but greater on the front side than on
the back with supercritical flow across the barrier. Supercritical flow from
front to back across the barrier occurs if the water level height above the
barrier on the back side is less than or equal to 2/3 the water level height
above the barrier on the front side (i.e., RBARWL2 < 0.667*RBARWL1).
QN2(k,j) = -(2/3)*RAMP*BARINCFSP(k,j)*RBARWL1*((2/3)*RBARWL1*G)**0.5
Case
5 – water level above the barrier height but greater on the back side than on
the front with subcritical flow across the barrier. Subcritical flow from back
to front across the barrier occurs if the water level height above the barrier
on the front side is greater than 2/3 the water level height above the barrier
on the back side (i.e., RBARWL1 > 0.667*RBARWL2).
QN2(k,j) = RAMP*BARINCFSB(k,j)*RBARWL1*(2*G*(RBARWL2-RBARWL1))**0.5
Case
6 – water level above the barrier height but greater on the back side than on
the front with supercritical flow across the barrier. Supercritical flow from
back to front across the barrier occurs if the water level height above the
barrier on the front side is less than or equal to 2/3 the water level height
above the barrier on the back side (i.e., RBARWL1 < 0.667*RBARWL2).
QN2(k,j) = (2/3)*RAMP*BARINCFSP(k,j)*RBARWL2*((2/3)*RBARWL2*G)**0.5
where
RBARWL1 = ETA1(NBVV(k,j))-BARINHT(k,j) = water height above the
barrier on the front side of the barrier
RBARWL2 = ETA1(IBCONN(k,j))- BARINHT(k,j) = water height above the
barrier on the back side of the barrier
ETA1(NBVV(k,j)) = water level computed
at the previous time step on the front side of the barrier
ETA1(IBCONN(k,j)) = water level
computed at the previous time step on the back side of the barrier
These formulae are given by
Leendertse (Aspects of SIMSYS2D – A System for Two-Dimensional Flow
Computation, Rand/R-3572-USGS, 1987) and are simply the formulae for a broad
crested weir (e.g., see Henderson, Open Channel Flow, section 6.6).
See also General Notes for Normal Flow Boundary Conditions
