Predicting discharge coefficient of compound broad-crested weir by using genetic programming (GP) and artificial neural
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ORIGINAL PAPER
Predicting discharge coefficient of compound broad-crested weir by using genetic programming (GP) and artificial neural network (ANN) techniques Farzin Salmasi & Gürol Yıldırım & Azam Masoodi & Parastoo Parsamehr
Received: 6 December 2011 / Accepted: 8 February 2012 / Published online: 7 March 2012 # Saudi Society for Geosciences 2012
Abstract Compound broad-crested weir is a typical hydraulic structure that provides flow control and measurements at different flow depths. Compound broad-crested weir mainly consists of two sections; first, relatively small inner rectangular section for measuring low flows, and a wide rectangular section at higher flow depths. In this paper, series of laboratory experiments was performed to investigate the potential effects of length of crest in flow direction, and step height of broad-crested weir of rectangular compound cross-section on the discharge coefficient. For this purpose, 15 different physical models of broad-crested weirs with rectangular compound cross-sections were tested for a wide range of discharge values. The results of examination for computing discharge coefficient were yielded by using multiple regression equations based on the dimensional analysis. Then, the results obtained were also compared with genetic programming (GP) and artificial neural network (ANN) techniques to investigate the applicability, ability, and accuracy of these procedures. Comparison of results from the GP and ANN procedures clearly indicates that the ANN technique is less efficient in comparison with the GP algorithm, for the determination of discharge coefficient. To examine the accuracy of the results yielded from the GP and ANN procedures, two performance indicators (determination coefficient (R2) and root mean square error F. Salmasi (*) : A. Masoodi : P. Parsamehr Department of Water Engineering, Faculty of Agriculture, Tabriz University, Tabriz, Iran e-mail: [email protected] G. Yıldırım Civil Engineering Department, Hydraulics Division, Engineering Faculty, Aksaray University, 68100 Aksaray, Turkey e-mail: [email protected]
(RMSE)) were used. The comparison test of results clearly shows that the implementation of GP technique sound satisfactory regarding the performance indicators (R2 00.952 and RMSE00.065) with less deviation from the numerical values. Keywords Broad-crested weir . Compound . Discharge coefficient . Genetic programming (GP) . Artificial neural network (ANN) . Soft computing
Introduction The techniques used in making discharge measurements at gauging stations (in rivers, canals, etc.) are important. The use of portable instrument like kinds of weirs, flumes, floats, and volumetric tank are common. The US Geological Survey makes thousands of stream flow measurements each year. Discharges measured range from a trickle in ditch to a flood on the Amazon. Several methods are used (Rantz 2005). A weir is a simple device for discharge measurement and flow control in open channels, such as canals and flumes. Many researchers have studied the head–d
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