Author(s): Jalil Abrishami; Ehsan Bahrami Jovein; Seyed Mohammad Ghaneeizad; Joseph F. Atkinson

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Keywords: Unsubmerged vane; Sharp bend; Bank stability; Secondary flow; Numerical modelling

Abstract: Unsubmerged vanes were studied experimentally and numerically as a tool for stream restoration and to improve bank stability in sharp bends. Five cases were investigated: one case with no vane and four cases with different configurations of vanes. The experiments were performed to directly evaluate the effects of two configurations of vanes on mean longitudinal velocity, and to provide data for confirmation of the numerical model. Results showed that when no vane was present high velocity occurs near the inner bank within the bend and then moves toward the outer bank just downstream of the bend. Placement of central unsubmerged vanes within the bend successfully reduced the high velocity near the inner bank, avoided the attack to the outer bank and decreased the superelevation within the bend. A numerical model developed with ANSYS FLUENT was used to extend the experimental results to consider two asymmetric configurations. Modelling results showed that central unsubmerged vanes are also able to decrease average turbulent kinetic energy (by about 16%), secondary flow (by about 45%) and bed shear stress (by about 17%), relative to the no-vane case. In contrast, asymmetric vanes significantly enhanced the flow turbulence (by about 1 order of magnitude), although they decreased the secondary flow by about 55%. The asymmetric cases also doubled the maximum bed shear stress. These outcomes provide useful information for the use of unsubmerged vanes in a variety of potential applications in stream restoration.

DOI: https://doi.org/10.1080/15715124.2017.1411928

Year: 2019