Abstarct: In the recent years, Computational Fluid Dynamics (CFD) is extensively used for solution of hydraulic engineering problems. A large number of hydraulic problems have been solved using CFD, such as problems in complex flows in closed pipes. Physical modeling is more expensive in both time costs and also has some limitations in comparison with CFD. There are some commercial, general purpose CFD programs for solution of fluid flows. FLUENT is one of the most famous CFD programs for solution of hydraulic engineering problems which can be used for a vast variety of flows. In this study, loss coefficients in bends are computed, by modeling turbulent flow using FLUENT Software. Different turbulence models were used and the best model was determined by comparing numerical and experimental results. Two sets of experimental results were available. In the first set, Reynolds number were 200000 for 45o and 90o bends and radious of bend over diameter of pipe (r/d) from 2 to 15 and for smooth pipe. In the second set Reynolds number were more than 220000 for 90o bend and r/D from 2 to 10 and for smooth pipes. For both sets comparison between numerical and experimental results were carried out. The results of this research showed that, the FLUENT Code is able to simulate flows in the bends and also the best turbulence model for determining loss coefficient of bends was Low-Re Stress-Omega. In addition, it was found that the loss coefficient of bend had no relation with bend diameter and it only was a function of r/D.