Abstract
The conditional double-averaged streamwise velocity, spatially averaged (SA) turbulence and dispersive quantities in flows over a water-worked gravel bed (WGB), and a screeded gravel bed (SGB) were studied. The effects of the temporal and advective bursting events on the WGB and SGB flows were analyzed by measuring the instantaneous flow field using a particle image velocimetry system. The flow conditions (flow rate and flow depth) were maintained the same in both the beds. The SA turbulence and dispersive quantities studied were the SA Reynolds shear and normal stresses, SA turbulent kinetic energy fluxes, dispersive shear and normal stresses, and dispersive kinetic energy fluxes. In experimental beds, owing to the water work, the WGB exhibited a spatially organized roughness structure as compared with a randomly organized roughness structure in the SGB, resulting in a higher WGB roughness than the SGB one. Analysis of the temporal bursting events revealed that the conditional SA turbulence quantities corresponding to the temporal sweeps were dominant within the roughness layer, whereas those corresponding to the temporal ejections govern above the roughness layer. Analysis of the advective bursting events indicated that the dispersive quantities involving advective sweeps were the key mechanism within the roughness layer, whereas those involving advective ejections were the prevailing mechanism in the main flow layer. The comparison of the results in the WGB and SGB flows elucidated that owing to the higher WGB bed roughness than the SGB one, the conditional SA turbulence and dispersive quantities in the WGB were greater than those in the SGB. Within the roughness layer, the bursting events in the WGB were more persistent and frequent than those in the SGB.
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Data Availability Statement
Some or all data, models, or code generated or used during the study are available from the corresponding author by request.
Acknowledgments
The first author is thankful to the University of Calabria, Italy for the invitation to work in the Laboratorio “Grandi Modelli Idraulici”. The work was partially funded by the JC Bose Fellowship project (JBD).
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Information & Authors
Information
Published In
Journal of Hydraulic Engineering
Volume 146 • Issue 2 • February 2020
Copyright
©2019 American Society of Civil Engineers.
History
Received: Nov 29, 2018
Accepted: Jun 7, 2019
Published online: Nov 27, 2019
Published in print: Feb 1, 2020
Discussion open until: Apr 27, 2020
ASCE Technical Topics:
- Advection
- Engineering fundamentals
- Flow (fluid dynamics)
- Flow measurement
- Flow rates
- Fluid dynamics
- Fluid mechanics
- Hydraulic engineering
- Hydraulic properties
- Hydraulic roughness
- Hydrologic engineering
- Measurement (by type)
- River and stream beds
- River engineering
- Rivers and streams
- Shear stress
- Stress (by type)
- Structural analysis
- Structural engineering
- Turbulence
- Turbulent flow
- Water and water resources
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