FLOW STRUCTURES AND CHANGES DUE TO MOTIONS OF SUSPENDED LOADS OF TURBULENT FLOW OVER ROUGHENED OPEN-CHANNEL WITH SECONDARY FLOW OF PRANDTL'S SECOND KIND

Abstract

 Three-dimensional numerical experiment of turbulent flow over narrow (b/h=1.41) open channel rough surface with roughness elements laid on the bottom were conducted to investigate changes in the flow structure and turbulence structure when suspended loads are added. Main velocity and secondary flow velocity profiles were distorted in the vicinity of the densely arranged roughness elements, but the longitudinal changes were small at higher locations. The secondary flow cells formed due to the imbalance between the Reynolds stress gradient and the pressure gradient overlap with the flow over the roughness elements and the flow that dips into the roughness valley, resulting in a longitudinal change in the secondary flow velocity distribution and a larger secondary flow velocity magnitude than in an open channel smooth surface turbulent field. The presence of suspended particles suppresses the transport of the vertical Reynolds stress due to velocity fluctuations at the bottom corner, which results in a reduction in the magnitude of the secondary flow velocity.