Transport and deposition of fine sediment in open channels with different aspect ratios

摘要

This paper investigates by means of several large eddy simulations how the channel aspect ratio affects the transport and settling of suspended sediments. The numerical method is successfully validated using data of a physical experiment of fine sediment net deposition in an open channel flow. The channel aspect ratio, A, is known to be the determining factor for the development, strength and distribution of the turbulence-driven secondary flow, and it is demonstrated that A influences the primary flow, turbulence quantities and the transport and fate of fine sediments. The secondary flow locally supports or hinders the falling of fine sediment particles in a turbulent flow, which results in a non-uniform deposition of fine sediments over the cross-section. While the channel aspect ratio has a large influence on the distribution of suspended sediments within the cross-section, its effect on the cross-sectional averaged deposition is negligibly small.