University of Tehran Press Iranian Journal of Soil and Water Research 2008-479X 48 4 2017 11 22 Estimation of the longitudinal dispersion coefficient using the dimensional analysis in surface water flows Estimation of the longitudinal dispersion coefficient using the dimensional analysis in surface water flows 759 769 64149 10.22059/ijswr.2017.219737.667566 FA MEHDI MOHAMMADI GHALENI Researcher, Ministry of Power and Energy Kumars Ebrahimi University of Tehran Mohammad Hossein Omid University of Tehran Journal Article 2016 11 15 Longitudinal dispersion coefficient is one of the most important parameters for the solution of the advection-dispersion equation. In this paper a new equation for predicting the longitudinal dispersion coefficient in surface water streams is presented. To archive this aim, a collection of 176 sets of measured field data from different canal and rivers were used, involving the dimensional analysis. Then the performance of the new equation was compared with 18 selected of well-known empirical equations, using the above mentioned data. The results show that the new equation has a twice precision in contrast to the other equations. In the other words, the calculated of the average percentage errors between the predicted and measured data for the proposed new equation was less than ±100 percent. Also, the mean absolute error and root mean square for the new equation were obtained equal to 0.34 and 0.03, respectively, which are less than other equations. Longitudinal dispersion coefficient is one of the most important parameters for the solution of the advection-dispersion equation. In this paper a new equation for predicting the longitudinal dispersion coefficient in surface water streams is presented. To archive this aim, a collection of 176 sets of measured field data from different canal and rivers were used, involving the dimensional analysis. Then the performance of the new equation was compared with 18 selected of well-known empirical equations, using the above mentioned data. The results show that the new equation has a twice precision in contrast to the other equations. In the other words, the calculated of the average percentage errors between the predicted and measured data for the proposed new equation was less than ±100 percent. Also, the mean absolute error and root mean square for the new equation were obtained equal to 0.34 and 0.03, respectively, which are less than other equations. https://ijswr.ut.ac.ir/article_64149_744992088a6150ca017249a05de66569.pdf