Influence of Negatively Buoyant Jets on a Strongly Curved Open-Channel Flow Using RANS Models with Experimental Data

Xueming Wang,Colin D Rennie,Abdolmajid Mohammadian

doi:10.3390/w14030347

Abstract

Experimental and numerical studies of flow structures in a strongly curved 135-degree laboratory flume were carried out to investigate the influence of negatively buoyant jets using the finite volume method. The performance results of three different turbulence models were investigated by comparing the numerical results with the experimental measurements. The present study demonstrates that fully 3D numerical models are capable of simulating the primary flow pattern in a strongly curved channel with the presence of a negatively buoyant jet. The comparison also shows that the k-omega SST model can satisfactorily predict some of the smaller flow features in bend flow, such as the inner bank circulation cell and the overall form of the vorticity distributions. It was found that the flow distribution and the strength of secondary flow vary due to the interaction between the jet mixing behavior and the secondary flow in the channel bend. The presence of negatively buoyant jets attenuated the development of the outer bank cell as salinity increased. In the inner bank region, flow separation was strengthened by the participation of the negatively buoyant jets.

Highlights

The investigation of flow structures in open channel bends is of great importance in hydraulic and environmental engineering sciences
Subjects related to super-elevation and bank erosion/shifting, bed scouring and sediment transport, migration of meanders and shear stress redistribution, as well as heat and salinity transfer have been proven to be attributed to river curvature [1]
A special feature of a curved open channel is the existence of secondary flow, resulting from the combination of lateral pressure gradients and centrifugal forces, i.e., the inclined free surface yielded transverse pressure gradient cannot balance the centrifugal force, which causes the water molecules at the bottom to move towards the inner bend and particles at the water surface to move towards the outer bend [2]

Summary

Introduction

The investigation of flow structures in open channel bends is of great importance in hydraulic and environmental engineering sciences. A special feature of a curved open channel is the existence of secondary flow, resulting from the combination of lateral pressure gradients and centrifugal forces, i.e., the inclined free surface yielded transverse pressure gradient cannot balance the centrifugal force, which causes the water molecules at the bottom to move towards the inner bend and particles at the water surface to move towards the outer bend [2]. The magnitude of the cross-stream motion, which is responsible for velocity redistribution and boundary shear stress, can be as much as 10–40% of the bulk streamwise velocity [3].

Methods

Results

Discussion

Conclusion