Reliability of the full equation model (FEQ) for the solution of steady-state and unsteady flows in open channels and rivers
Abstract
The reliability of the Full EQuation numerical Model (FEQ) to solve the de Saint Venant equations, is evaluated by analyzing the stability and accuracy of the simulation result, when the model is applied to steady state flow and to unsteady flow conditions over the reach or computational element component of an open channel. In the case of steady state flow, the FEQ model results are compared to the exact solution of the gradually varied flow equation, applied to the case of a wide-horizontal rectangular channel. A first order approximation numerical model, a second order approximation numerical model, and the HEC-2 program are also included in the reliability study of the FEQ model to simulate steady state flows. The unsteady flow test is constituted by peaked hydrographs superimposed on the uniform flow conditions. The unsteady flow results from FEQ are compared to the solution of the de Saint Venant equations using the Method of Characteristics. This method has been proved to give stable and accurate results when the time step in the integration is kept very small, that is when the number of subreaches is large. A self comparison analysis for different number of reaches is done to obtain the optimal number of reaches that gives the most stable and accurate results in both models. In each case the comparison is done using graphical and error analysis methods. From these comparisons, the FEQ model shows very stable and accurate results with respect to the other models. For the steady state flow the maximum error found with respect to the exact solution is on the order of 2%. In the case of the unsteady flow this value was 0.05%. The reliability of the model is therefore rather high in simulating both; steady state and unsteady flows in open channels.
Degree
Ph.D.
Advisors
Giorgini, Purdue University.
Subject Area
Civil engineering
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