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open channel flow - mowafi3m - 01-23-2011 open channel flow
General HEC-6 (HEC, 1991) is a one-dimensional movable boundary open channel flow and sediment model designed to simulate changes in river profiles due to scour and deposition over fairly long time periods (typically years, although applications to single flood events are possible). The continuous flow record is broken into a sequence of steady flows of variable discharge and duration. For each flow a water surface profile is calculated thereby providing energy slope, velocity, depth, etc. at each cross section. Potential sediment transport rates are then computed at each section. These rates, combined with the duration of the flow allow for a volumetric accounting of sediment for each reach. The amount of scour or deposition at each section is then computed and the cross section shape adjusted accordingly. The computations then proceed to the next flow in the sequence and the cycle is repeated beginning with the updated geometry. The sediment calculations are performed by grain size fraction thereby allowing for the simulation of hydraulic sorting and armoring. Features of the model include: capability to analyze networks of streams, automatic channel dredging, various levee and encroachment options, and several options for computation of sediment transport rates. Experience has shown that successful application of movable boundary models may require substantial effort to reproduce field observations, i.e. calibration. This document complements the HEC-6 User's Manual (HEC, 1991) and provides guidelines for calibration and application. The general topic of application and calibration of numerical river models is thoroughly covered in Cunge, et al. (1980). This document provides guidance on the engineering aspects of applying HEC-6; it is, therefore, a supplement to the HEC-6 User's Manual. Originally published in 1981, this edition contains substantial new material based on program enhancements and applications experience gained since then. This document was prepared by D. Michael Gee, Training Division, HEC. William A. (Tony) Thomas, Hydraulics Laboratory, WES, provided most of the concepts and material included herein. Vern Bonner was Chief, Training Division and Darryl W. Davis, Director, HEC, during preparation of this report. Code: *************************************** |