Flow Structure and Channel Stability at the Site of a Deep Scour Hole, Mackenzie Delta, Canada

Spyros Beltaos; Bommanna G. Krishnappan; Robert Rowsell; Tom Carter; Roger Pilling; Paul Emile Bergeron

doi:10.14430/arctic4199

Persistence of a scour hole on the East Channel of the Mackenzie Delta, N.W.T.

Canadian Journal of Civil Engineering ◽

10.1139/l00-022 ◽

2000 ◽

Vol 27 (4) ◽

pp. 798-804 ◽

Cited By ~ 6

Author(s):

Steven R Fassnacht ◽

F Malcolm Conly

Keyword(s):

Average Rate ◽

Temporal Stability ◽

Mackenzie Delta ◽

River Channels ◽

Channel Stability ◽

Practical Concern ◽

Scour Hole ◽

Lateral Erosion ◽

Morphologic Data ◽

Mackenzie River

Anomalies in the bathymetry of river channels are of great practical concern for designing sub-bed pipeline crossings. Of particular interest is the long-term stability of deep holes. Bathymetric evidence indicates that one unusually deep hole in the East Channel of the Mackenzie River, referred to as a scour hole, has existed as early as 1956. Detailed hydraulic and morphologic data were first collected in 1985, and again in 1992 to assess the spatial and temporal stability of the feature. Even with a record flood on the Mackenzie River in 1988, the hole, with a maximum depth approaching 30 m, was vertically stable over the 7-year period. However, lateral erosion and sedimentation have resulted in a shift in the horizontal position of the scour hole, with a maximum horizontal erosion of approximately 2 m/a. The average rate of lateral outward movement was observed to be 0.8 m/a.Key words: Mackenzie Delta, rivers, fluvial sediment, channel stability, scour, scour hole.

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Modelling of three-dimensional flow velocities in a deep hole in the East Channel of the Mackenzie Delta, Northwest Territories

Canadian Journal of Civil Engineering ◽

10.1139/l07-054 ◽

2007 ◽

Vol 34 (10) ◽

pp. 1312-1323 ◽

Cited By ~ 8

Author(s):

Bahram Gharabaghi ◽

Chris Inkratas ◽

Spyros Beltaos ◽

Bommanna Krishnappan

Keyword(s):

Shear Stress ◽

Three Dimensional ◽

Bed Shear Stress ◽

Mackenzie Delta ◽

Stress Distributions ◽

Deep Hole ◽

Flow Conditions ◽

Scour Hole ◽

Scour Holes ◽

The Stability

The Mackenzie River has several anomalous deep scour holes in a number of river channels in its delta. Proposed gas pipeline crossings have renewed interest in studying the stability of these scour holes. The main goal of this research project was to study flow velocity and bed shear stress distributions for a 30 m deep hole in the East Channel of the Mackenzie Delta as a first step toward assessing the stability of the scour hole and the risk of its migration during various flow conditions. In this study, a three-dimensional (3D) finite element flow model, FLUENT, using the renormalization group (RNG) k-ε turbulence model (where k is the turbulent kinetic energy and ε is the turbulence dissipation rate) was set up for the scour hole and calibrated using detailed measurements of 3D flow velocities, obtained with an acoustic doppler current profiler. The numerical model was then applied to predict flow velocity and bed shear stress distributions in and around the scour hole for three flow conditions (720, 1000, and 1400 m3/s). Results indicate that two vortices are formed in the river elbow above the scour hole. As the flow rate changed, the sizes of the vortices varied. The region upstream of the hole experienced the greatest magnitudes of bed shear stress.Key words: computational fluid dynamics, finite element, bed shear stress, deep hole, flow reversal.

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Residual Flow Structure at a Scour-hole in Bahia Blanca Estuary, Argentina

Journal of Coastal Research ◽

10.2112/010-nis.1 ◽

2005 ◽

Vol 214 ◽

pp. 784-796 ◽

Cited By ~ 7

Author(s):

Jorge O. Pierini ◽

Gerardo M. E. Perillo ◽

María E. Carbone ◽

Fabián M. Marini

Keyword(s):

Flow Structure ◽

Residual Flow ◽

Bahía Blanca Estuary ◽

Scour Hole ◽

Blanca Estuary

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Three-Dimensional Numerical Investigations of the Flow Pattern and Evolution of the Horseshoe Vortex at a Circular Pier during the Development of a Scour Hole

Applied Sciences ◽

10.3390/app11156898 ◽

2021 ◽

Vol 11 (15) ◽

pp. 6898

Author(s):

Ahmed M. Helmi ◽

Ahmed H. Shehata

Keyword(s):

Shear Stress ◽

Flow Structure ◽

Three Dimensional ◽

Turbulence Models ◽

Horseshoe Vortex ◽

Bed Shear Stress ◽

Scour Hole ◽

Scouring Depth ◽

Mean Size ◽

Stress Variations

In the current study, a three-dimensional CFD model is utilized to investigate the variation of the flow structure and bed shear stress at a single cylindrical pier during scour development. The scour development is presented by seven solidified geometries of the scour hole, collected during previous experimental work at different scour stages. Different turbulence models are evaluated and the (k-ω) model is chosen due to its relative accuracy in capturing the flow oscillation and vortex shedding at the pier downstream side with personal computer computational and storage resources. The numerical results are verified against dimensionless parameters from different previous experimental works. This research describes in detail the flow structure and bed shear stress variations through seven stages of the scour hole development. The dimensionless area-averaged circulation coefficient (Ψi) is developed to evaluate the changes in the vortex strength through the scouring process by eliminating the calculation area effect. It was concluded that the circulation in the (Y) direction is the main driving factor in the development of the scour hole more than the circulation in the (X) direction. The ratio between the horseshoe vortex (HV) mean size and the scouring depth (DV/dS) in addition to the location of the maximum bed shear stress are investigated during different stages of the scour development.

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