[Next Section] [Previous Section] [Table of Contents]

Full Equations Utilities (FEQUTL) Model for the Approximation of Hydraulic Characteristics of Open Channels and Control Structures During Unsteady Flow

U.S. GEOLOGICAL SURVEY WATER-RESOURCES INVESTIGATIONS REPORT 97-4037

1. INTRODUCTION


In unsteady flow, some aspect of the flow (velocity, depth, pressure, and others) is changing with time. Most flows of interest to hydraulic engineers, hydrologists, and planners are unsteady and may be considered one dimensional (that is, acceleration is substantial only in the longitudinal direction). In standard hydraulic- engineering practice, many problems involving one-dimensional, unsteady flows have been approximated by application of steady flows or piecewise-steady flows wherein storage-outflow relations are derived for channel reaches from a steady-flow hydraulic analysis [in the U.S. Army Corps of Engineers (1990a) Water Surface Profiles model HEC-2] and applied in simple hydrologic-routing methods [in the U.S. Army Corps of Engineers (1990b) Flood Hydrograph Package HEC-1]. Simulation of one-dimensional, unsteady flow in a complex stream system that contains many hydraulic structures is practicable with the recent increases in the computational speed and storage capabilities of computers.

The Full EQuations (FEQ) model (Franz and Melching, 1997) is a highly flexible and robust model for simulation of one-dimensional, unsteady flow in open channels and through control structures. An extensive description of the hydraulic characteristics of the stream system to be simulated is required in FEQ. At a minimum, the geometry of the stream channels must be described. In addition, the hydraulics of a variety of structures, including culverts, bridges, spillways, contractions, and expansions, either natural or constructed, may need to be described. The variety of structures that can be present in a stream system is practically unlimited. Some of these structures were designed and constructed thoughtfully, but many were not. Therefore, one of the major tasks of simulating the hydraulic behavior of a stream system is the description of the hydraulic characteristics of the various structures in that system. The utility program Full EQuations UTiLities (FEQUTL) has been developed to make the description of the hydraulic characteristics of the stream system easier. A variety of look-up tables are computed in FEQUTL to describe channel cross sections and hydraulic control structures to facilitate simulation of unsteady flow with FEQ.

Stream slopes are relatively flat and flood plains are relatively broad throughout Illinois. Further, the counties in the Chicago, Ill., metropolitan area are undergoing rapid urbanization. These factors have resulted in increased interest in application of unsteady-flow analysis for flood-plain delineation, flood warning, flood- control reservoir design and operation, and other applications in rapidly urbanizing counties in Illinois. Because a wide variety of hydraulic structures in the stream system could be simulated in FEQ, extensive testing and documentation were done by the U.S. Geological Survey (USGS) and cooperating agencies. The Illinois Department of Natural Resources, Office of Water Resources, and the County of Du Page, Department of Environmental Concerns, cooperated with the USGS and Linsley, Kraeger Associates Ltd. to document the procedures applied in FEQUTL to compute function tables that relate flow to upstream and downstream water-surface elevation for cross sections and hydraulic control structures in open-channel systems (streams) simulated with FEQ.

1.1 Purpose and Scope

1.2 Look-up Tables
1.3 Procedure for Computation of Function Table for Use in Simulation of Unsteady Flow with the Full EQuations Model

[Next Section] [Previous Section] [Table of Contents]