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Roughness effect on turbulent flow structure beneath a simulated ice jam

Author(s): Baafour Nyantekyi-Kwakye; Hoda Pahlavan; Shawn P. Clark; Mark F. Tachie; Karen Dow

Linked Author(s): Hoda Pahlavan, Shawn Clark, Mark Tachie, Karen Dow

Keywords: Bed shear stress; coherent structures; ice jam; pressure gradient; river ice; surface roughness

Abstract: Detailed velocity measurements beneath a modelled ice jam with both smooth and rough surfaces were conducted using acoustic Doppler velocimetry and particle image velocimetry. The experiments were conducted at Reynolds numbers based on hydraulic diameter of 28,400 and 72,000. The topography of the mean flow field revealed acceleration and deceleration of the flow within the upper and lower toe sections of the modelled jam, respectively. The introduction of surface roughness increased flow blockage, thereby increasing the maximum streamwise mean velocity within the upper toe section. The estimated bed shear stress attained a maximum within the toe section, with roughness significantly increasing the values. Large vortical structures dominated the flow over the rough surface compared to the smooth case. The present results suggest the possibility of enhanced sediment transport beneath the modelled jam when both bed and ice jam were roughened.


Year: 2019

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