Full Equations Utilities (FEQUTL) Model for the Approximation of Hydraulic Characteristics of Open Channels and Control Structures During Unsteady Flow
The purpose of this report is to document the procedures applied in the Full EQuations UTiLities (FEQUTL) model to compute function tables that relate flow to upstream and downstream flow depth for cross sections and hydraulic control structures in open-channel systems (streams) simulated with the Full Equations (FEQ) model. The FEQUTL model and example inputs and outputs may be obtained by electronic retrieval from the World Wide Web (WWW) at http://water.usgs.gov/software/feq.html and by anonymous File Transfer Protocol (FTP) from water.usgs.gov in the pub/software/surface_water/feq directory. This report describes the procedures applied in FEQUTL to compute the hydraulic characteristics of channel cross sections, expansions, contractions, bridges, culverts, embankments, weirs, closed conduits (circular, rectangular, and pipe-arch shapes), dam failures, floodways, and underflow gates (sluice and tainter gates). The report begins with a description of the variety of function tables required to list the hydraulic characteristics of the stream features listed to facilitate simulation of unsteady flow with FEQ. The procedures applied to approximate the hydraulic characteristics of open channels (cross sections, expansions, and contractions) are discussed. The procedures applied to approximate the hydraulic characteristics of hydraulic control structures are developed.
Previous research on the hydraulics of control structures forms the basis of the procedures applied to approximate the hydraulics of control structures. This research was done to describe flow hydraulics for a single, steady-flow design condition and, thus, does not provide complete information on flow transitions (for example, between free- and submerged-weir flow) that may result in unsteady flow. Therefore, the procedures applied to approximate the hydraulics of flow transitions for culverts, embankments, weirs, and underflow gates are discussed in detail because these include new techniques that are not well known in the hydraulic literature but produce reasonable simulation results. Finally, the input for FEQUTL and the error messages and warnings issued in model computations are presented.