Developing finite volume method (FVM) in numerical simulation of flow pattern in 60° open channel bend

In meandering rivers, the flow behavior is very complex due to topography and flow depth changes. In general, effective forces on bend flow pattern include centrifugal force due to non-uniformity of the vertical velocity profile and radius pressure gradient induced by the lateral slope of water surface. In this paper, the 60° bend flow pattern is simulated by developing FLUENT computational software based on finite volume method (FVM), numerically. The k-ε (RNG) turbulence model and volume of fluid (VOF) method are used for turbulence and flow depth modeling. The FVM numerical results are verified by existing experimental data in velocity and flow depth. The results illustrate that the FVM model has high accuracy in prediction flow variables in the bend. As the average value of root mean square error (RMSE) and mean absolute percentage error (MAPE) values between the observational and numerical results for depth-averaged velocity (DAV) in the different transverse profile are 4.5 and 9%, respectively, which is an acceptable error percentage. The advanced software can well simulate the both major and minor secondary current cells with opposite rotation direction in the vicinity of channel bed and vicinity the water level in the outer wall, respectively. By the development of the major and minor secondary currents in sections located 40 (cm) after the bend, longitudinal velocity shift, and the high-velocity zone moves further to the outer wall (and the channel bed) in depth. Therefore, it can be said the developing FLUENT software can be utilized in practical cases in design and execution of curved channel.