Author(s): Shuqing Yang

Linked Author(s):

Keywords: Secondary flow; Channel flow; Reynolds stress; Shear flow; Three-dimensional flow;

Abstract: This paper describes the conditions for initiation and maintenance of secondary currents in open channel flows. By analyzing the Reynolds equation in the wall-normal and wall-tangent directions, this study reveals that, like other type vortices, the secondary currents are originated from a near-boundary region, its magnitude is proportional to the lateral gradient of near-wall region velocity, and its direction always is always parallel to the solid boundary and points to the region with high velocity. Subsequently, the near boundary flow creeps into the main flow and drives circulation within a region enclosed by lines of zero total shear stress, then leads to anisotropy of turbulence in the main flow region. Typical secondary currents in open channel flows are discussed, such as that induced by sidewall, sand ridges/sediment stripes, compound channel flows etc, all cases support the new mechanism.

DOI: https://doi.org/10.3850/38WC092019-0687

Year: 2019