Turbulent flow in meandering open channels is one of the most complicated and unpredictable turbulent flows as the interaction of various forces, such as pressure gradient, centrifugal force, and wall shear stresses severely affect the flow pattern. In order to improve significance in engineering application, understanding the overall flow characteristic is the focus. This paper presents the results of numerical and experimental investigations of flow in a 180° mild bend, which is close to criticality with curvature ratio R/B = 3. Considering the characteristic of various models, three-dimensional (3D) re-normalization group (RNG) k–ε model was adopted to simulate the flow efficiently. Governing equations of the flow were solved with a finite-volume method. The pressure-based coupled algorithm was used to compute the pressure. The flow velocities were measured experimentally with Micro acoustic Doppler velocimeter. Good agreement between the numerical results and measurements indicated that RNG k–ε model can successfully predict this flow phenomenon. The flow pattern in this bend is influenced widely by the secondary flow. The variations of velocity components, streamlines, secondary flow, and wall shear stresses are analysed in the study. Some newly discovered phenomenon in this special state are worth noting.

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