CGRG Bibliography of Canadian Geomorphology
Search Results
Author : Haltigin, T.W.; Biron, P.M.; and Lapointe, M.F.
Date : 2003.
Title : Three-dimensional numerical modeling of flow dynamics around stream deflectors.
Publication : Canadian Geophysical Union. Annual Meeting, May 10 -14, 2003. Banff Centre, Banff, Alberta.
Issue :
Page(s) :
Abstract
Stream deflectors are one of several instream restoration structures used to rehabilitate degraded fish habitats. However, the success of these projects has been limited due to the trial-and-error approach with which they are often designed and implemented, as well as the lack of understanding of the detailed flow dynamics around deflectors. This project uses a three-dimensional numerical model to examine the flow fields around these structures and to establish the relationship between flow behaviour, predicted bed shear stress, and known changes in bed topography. The model solves the fully three-dimensional form of the Reynolds-Averaged Navier-Stokes equations in conjunction with the Renormalized Group Theory k-å turbulence model. Flow around paired deflectors of various angles and contraction ratios are simulated for both stationary and mobile beds. Results are compared against detailed flume measurements of three-dimensional velocity and shear stress. In general, velocity predictions match well with the laboratory measurements. Extensive flow separation and recirculation characterize the velocity field; flow reattachment distance is greatest along the banks downstream of the deflectors, and strong vertical recirculation pockets are present both upstream of and in the lee of the structures. Predicted shear stress is greatest between the deflectors, but does not fully explain the scour viewed in the laboratory. Scour depths are greatest where the combination of shear stress and downwelling (negative vertical velocity) is maximized, while varying the deflector angle results in a shift in locations of highest shear stress and scour. This model will be adapted for application to a natural river in which deflectors have previously been installed. The success of this research may result in an increased reliance on numerical simulations prior to structure installation in future restoration projects.
Bibliography of Canadian Geomorphology