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Full Equations (FEQ) Model for the Solution of the Full, Dynamic Equations of Motion for One-Dimensional Unsteady Flow in Open Channels and Through
Control Structures
U.S. GEOLOGICAL SURVEY WATER-RESOURCES INVESTIGATIONS REPORT 96-4240
8. BOUNDARY AND INITIAL CONDITIONS
Simulation of unsteady flow in a stream segment (branch) requires
information on the discharge and water-surface elevation at the
boundaries of the segment throughout time and at all points in the
system at some initial time, as described in section 5.3 "
Nature of Shallow-Water Waves." For a network of open
channels, the flow paths--branches, dummy branches, and level-pool
reservoirs--are separated by special features such as junctions
and hydraulic-control structures. Therefore, the system requires
internal boundary conditions at the flow-path end nodes connected
to special features, as well as external boundary conditions.
Internal boundary conditions, which are typically determined from
the hydraulic characteristics of the special features, are
available for a wide variety of special features simulated in FEQ.
This section details the internal and external boundary conditions
and the initial conditions simulated in FEQ.
The special features in the stream system are considered small
relative to the branches and level-pool reservoirs, so the
storage and momentum content in the special features are
negligible. Therefore, the equations of motion describing the
hydraulic characteristics of flow through the special features
that compose the internal boundary conditions are all
steady-flow relations. For some special features--a long
culvert is a simple example--this assumption is not valid.
This culvert may have to be represented as a branch in the form
of a storm sewer, not as a culvert, even though it has the
physical form of a culvert. The concern in simulation of
unsteady flow, however, is not on the physical form but on the
effect that the feature has on the flows of interest.
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8.1 Internal Boundary Conditions
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8.2 External Boundary Conditions
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8.3 Initial Conditions
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Last modified: Wed Nov 19 10:20:28 CST 1997