Turbulence-induced secondary flows in straight open channel with imposed transverse bed non-uniformities

• Main Author: Wang, Zhiqian
• Other Authors: Cheng Niansheng
• Format: Theses and Dissertations
• Language: English
• Published: 2008
• Subjects: DRNTU::Engineering::Civil engineering::Water resources
• Online Access: https://hdl.handle.net/10356/12042
• Institution: Nanyang Technological University

Characteristics of open channel flows can be significantly modified in the presence of secondary flows. This study aims to investigate time-mean characteristics of open channel flows subject to steady large-scale longitudinal vorticity, which are generated by longitudinal bedforms. Laboratory experiments are conducted for six types of bed configurations. The results demonstrate that the generated secondary flows generally appear as pairs of counter-rotating circulations across the primary flow. The streamwise velocity that is significantly modified by the cellular secondary flows can be well represented by a function proposed in the log-wake form. The analysis shows that the modified primary flow can be linearized so that a flow quantity can be generally decomposed into two components, one being related to the average base flow and the other symbolizing the perturbation caused by the bed configuration. This study also discusses effects of cellular secondary flows on the concentration distribution of suspended sediment.