Comparison of One-Dimensional HEC-RAS with Two-Dimensional ADH for Flow over Trapezoidal Profile Weirs

Two numerical models namely The U.S. Army Corps of Engineers River Analysis System (HEC-RAS) and The Adaptive Hydraulics (ADH) were evaluated and compared. The models were used to predict the water surface profile, determine the location of the hydraulic jump, and establish the head-discharge relationship of the trapezoidal profile weir. Various cases of steady free flow were examined on short- and broad-crested types of the weir. The effects of the weir height, crest length, face slope, flow rate, and tailwater depth were investigated. The simulation results were verified by laboratory measurements on twenty-seven weirs. It was found that the largest deviation of the prediction results from the measurements occurred in flow cases over short-crested weirs. It was also found that both HEC-RAS and ADH slightly underestimated the upstream water levels at lower flow rates and lower tailwater levels. Both computer programs could capture the overall features of the water surface profile with reasonable accuracy. However, the ADH profiles were more descriptive. ADH was also found more precise in determining the location of the hydraulic jump. On the other hand, HEC-RAS better described the head-discharge relationship. The absolute error in the upstream crest-referenced heads predicted by HEC-RAS was between 0.41 and 2.25% with an average of 1.45% with respect to the measurements, whereas that of ADH was between 0.76 and 3.85% with an average of 2.36%. Besides, HEC-RAS was found easier to use for this specific flow problem and its simulation time was significantly less than that of ADH.