Numerical study of flow dynamics around a stream restoration structure in a meandering channel

ABSTRACT

In this paper the flow around a streambank-attached in-stream structure – rock vane – installed in a meandering channel is investigated via large-eddy simulation (LES). LES is carried out for the case where the rock vane is installed along the outer bank of a field-scale, natural-like experimental meandering channel facility. Analysis of the simulated flow field shows that the rock vane acts to displace the upstream high-velocity core toward the channel centre and it effectively reduces the bed shear stress along the outer streambank. It is also found that the presence of the rock vane gives rise to the growth of the secondary flow cell formed along the outer streambank, which is often called the outer bank cell. Numerical results suggest that the growth of the outer bank cell and the subsequent displacement of the outer bank shear layer are responsible for the displacement of channel thalweg toward the channel centre.

Keywords:

• Large eddy simulation
• computational fluid dynamics
• river restoration
• river training

Acknowledgements

This work was supported by NSF grant EAR-0120914 (as part of the National Center for Earth-Surface Dynamics). The first author acknowledges that this research was partially supported by a grant (14CTAP-C077529-01) from the Infrastructure and Transportation Technology Promotion Research Program funded by the Ministry of Land, Infrastructure and Transport of the Korean government.

Notation

J	=	Jacobian of the geometric transformation
	=	transformation metrics,
	=	Cartesian velocity component
	=	contravariant volume flux
	=	components of the contravariant metric tensor,
p	=	pressure
ρ	=	density
µ	=	dynamic viscosity
µt	=	dynamic eddy viscosity
τij	=	sub-grid stress tensor
	=	Smagorinsky constant
Δ	=	LES filter size