Hydrodynamics and turbulence anisotropy for complex flow in a sinuous channel

Sinuous channel flows are the most natural form of alluvial streams. The complex flow in the channel bends has been the main focus of the study. This paper examines the flow velocity and the three-dimensional velocity fluctuations in a pure sinuous channel. The main focus of the study is on the characterization of turbulence anisotropy along the sinuous bend. Experiments were conducted in a sinuous channel of a rectangular cross-section to identify the turbulence present in the flow. Secondary flow, Reynolds shear stress, turbulent kinetic energy, and anisotropy turbulence were evaluated in the sinuous bend. The bend apex is composed of a large circulation cell at the center of the bend section. The maximum Reynolds shear stress (RSS) is located at the bend apex with the streamwise-transverse and transverse-vertical components of RSS showing high peaks of positive and negative values. This fact is in support of the secondary flow observed in this study. Anisotropic stress tensors were estimated at different bend sections and are shown to have greater contribution toward streamwise and transverse direction. Anisotropic invariant map (AIM) identified the turbulence at bend sections and varying flow depth. Twodimensional, cigar-shaped, and pancake-shaped turbulence was observed at the bend upstream and downstream. Isotropic turbulence was observed at the bend apex. Near the bed (z/h <= 0.2) and away from the bed (z/h >= 0.4), pancake-shaped and cigar-shaped turbulence was observed.

Automated summary

This paper examines the flow velocity and the three-dimensional velocity fluctuations in a pure sinuous channel and focuses on the characterization of turbulence anisotropy along the sinuous bend. The experimental results show the presence of a large circulation cell at the bend apex, with high peaks of positive and negative values of streamwise-transverse and transverse-vertical components of Reynolds shear stress. Anisotropic stress tensors have a greater contribution toward streamwise and transverse direction.