Author(s): Shalini Kashyap; Colin Rennie; Gavin Post; Ronald Townsend

Linked Author(s): Tsan-Wen Wang, Colin Rennie, Ronald Townsend, Shalini Kashyap

Keywords: No Keywords

Abstract: Flow patterns in a channel bend are significantly affected by channel geometry including the curvature ratio (bend radius/channel width), the width to depth ratio, and the bend angle. Hydraulically narrow streams (width/depth ≤ 10) with low curvature ratios are responsible for substantial soil loss in nature. In this University of Ottawa study, a three dimensional Reynolds Averaged Navier-Stokes (3D RANS) numerical model is employed to simulate flow in a 135° hydraulically narrow channel bend. Flow structures such as helical motion are resolved and related with shear stress distributions in the bend. Unlike previous 3D RANS models of flow in alluvial channel bends, the numerical model is validated with three-dimensional turbulent velocity measurements spatially distributed throughout the bend. Point velocity measurements were taken in the bend section of a 1.0 m wide mobile-bed river bend flume model with acoustic Doppler velocimeters (ADVs). Measurements were conducted at a width to depth ratio of less than 7 over an equilibrium clear-water alluvial bed morphology. The principal goal of the study is to better understand the complex nature of the flow structures generated in alluvial channel bends, with a view to improving the design of ‘stream barb' installations (a novel form of stream-bankerosion prevention structure).

DOI:

Year: 2009