Abstract
The secondary circulation in a meandering channel redistributes the velocity over the bend. However, the shift of primary flow by secondary currents is not quantitatively understood, due to the difficulty in isolating the role of curvature-driven secondary flow from that of topography-driven secondary flow in bed-deformed meanders. The influences of curvature-driven and topography-driven secondary currents on the redistribution of primary flow in sine-generated meandering channels were examined by CCHE2D. The model is calibrated using data measured in two sets of laboratory experiments including flat-bed flow and mobile-bed flow. Analysis indicated that topography-induced current mainly contributes to the redistribution of primary flow from inner to outer bank in the curved channels, rather than the secondary flow driven by curvature.
Highlights
Secondary flows in meanders, including curvaturedriven and topography-driven secondary currents, have been considered to be primarily responsible for redistributing or shifting the primary flow (Chen and Tang, 2012)
This study aims at analysing the redistribution of primary flow in sine-generated channels by numerical simulation of CCHE2D
The curvature and bed topography of a curved river play an important role in the analysis of various aspects of river engineering problems, such as river regulation, navigability, bank protection, and dispersion of heat and pollutants
Summary
Secondary (transverse) flows in meanders, including curvaturedriven and topography-driven secondary currents, have been considered to be primarily responsible for redistributing or shifting the primary (longitudinal) flow (Chen and Tang, 2012). The core of maximum primary flow will gradually run across the channel centreline and shift towards the outer bank of bends as the channel develops into a large-sinuosity one with a deformed bed. Both curvature-driven and topography-driven secondary flows contribute to the shifting process. Chen and Tang (2012) have evaluated the role of the two secondary currents in the evolution of sine-generated meanders by coupling Johannesson and Parker’s (1989) one-dimensional flow model with the bank erosion and retreat model (BERM). The above flow model adopts the first-order analytical solution of Navier-Stokes equations, which is assumed to be valid only for mildly-curved channels
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