Numerical Study of Channel Convergence Effects on Flow Pattern in 90 Degree Bends

As a result of topography changes along the open channels, designing the right bend is an essential. Channel width limits, such as existence of culverts beneath the roads and sharp changes in topographies, usually impel engineers to design non-prismatic or converging bends along the open channels. In this research the flow pattern in a 90o curved converging rectangular open channel is numerically investigated. A three-dimensional simulation was carried out using the commercial CFD package ANSYS-FLUENT. To obtain the most accurate pattern, five different turbulence models: standard k-ε, realizable k-ε, RNG k-ε, k-ω and RSM, along with the VOF free surface model were utilized to solve the 3D Navier-Stokes equations. The accuracy of the model was analyzed with observed data from experimental study of an ordinary 90o open channel curvature as a qualitative reference and the computed results of the present study were validated. The predicted results for the flow characteristics are in reasonable agreement with the experiment data. As extent of the work, a converging open channel bend was simulated and the velocity profiles and the flow separation after the bend are evaluated. It has been concluded that unlike the ordinary open channel bend, the minimum velocity in a converging channel occurs in different locations along the bend while the separation zone is eliminated. Concerning how it can affect the conveyance capacity and channel width, the issue could be attention-getting in the study of sedimentary processes of meandering rivers

کلیدواژه ها:

open channel bend ، converging bend ، volume of fluid ، turbulence modeling ، flow separation