The Flow Structure in the Narrow Gaps of Compound Channels: The Basic Flow

Abstract

In the present work, a methodology for the basic flow solution in complex form channels is presented. This methodology, which could be applied to any compound channel, implements an innovative and original solution strategy which solves in a simple way the apparent nonlinearity of the problem. The solution is computed using the finite element method. As an illustration, the methodology was applied to study flows in complex channels consisting of two rectangular channels connected through a rectangular slot. The effects of the slot position (placed either at the bottom or in the centre of the channels) and height on the velocity and wall shear stress distributions and overall friction were investigated. For small slot relative heights, the flow is essentially organized as parallel channel flows with almost no interaction between them and the overall channel friction factor is insensitive to the slot position. For larger gaps, the position of the slot becomes a determinant parameter. The presence of the slot and its relative height influence the entire flow distributions and the overall friction factor. The velocity profiles in the middle of the gap were studied, and their implications on the possibility of the development of hydrodynamic instabilities were considered.