Ehsan Yarmohammadi - Department of Water Engineering, Faculty of Agriculture, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran.
Fariborz Yosefvand - Department of Water Engineering, Faculty of Agriculture, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran.
Ahmad Rajabi - Department of Water Engineering, Faculty of Agriculture, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran.
Saeid Shabanlou - Department of Water Engineering, Faculty of Agriculture, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran.

In this paper, for the first time, the discharge coefficient of triangular plan form weirs is simulated by the extreme learning machine (ELM). ELM is one of the powerful and rapid artificial intelligence methods in modeling complex and non-linear phenomena. Compared to other learning algorithms such as back propagation, this model acts rapidly in the learning process and provides a desirable performance in processing generalized functions. In this study, the Monte Carlo simulation is used for examining capabilities of numerical models. Also, the k-fold cross validation method with k=5 is utilized for evaluating abilities of the ELM models. Then, six ELM models are introduced by means of the parameters affecting the discharge coefficient of triangular plan form weirs. After that, the superior model is identified by analyzing the results of the mentioned models. The superior model predicts discharge coefficient values with reasonable accuracy. This model simulates the discharge coefficient as a function of the flow Froude number, vertex angle of the triangular plan form weir, the ratio of weir length to its height, the ratio of flow head to weir height and the ratio of channel width to weir length. For the best model, the Mean Absolute Error, Root Mean Square Error and determination coefficient are computed 1.173, 0.012 and 0.967, respectively. Furthermore, examination of the influence of the input parameters indicates that the flow Froude number is the most influenced factor in modeling the discharge coefficient. Also, the error distribution showed that roughly 86 % of the superior model results had an error less than 2 %. Furthermore, a practical equation was provided to compute the discharge coefficient.

Discharge Coefficient, Extreme Learning Machine, Numerical modeling, Sensitivity analysis, Triangular plan form weir