Determining the Onset of Hydrodynamic Erosion in Turbulent Flow

Abstract

We revisit the longstanding question of the onset of sediment transport driven by a turbulent fluid flow via laboratory measurements. We use particle tracking velocimetry to quantify the fluid flow as well as the motion of individual grains. As we increase the flow speed above the transition to sediment transport, we observe that an increasing fraction of grains are transported downstream, although the average downstream velocity of the transported grains remains roughly constant. However, we find that the fraction of mobilized grains does not vanish sharply at a critical flow rate. Additionally, the distribution of the fluctuating velocities of non-transported grains becomes broader with heavier tails, meaning that unambiguously separating mobile and static grains is not possible. As an alternative approach, we quantify the statistics of grain velocities by using a mixture model consisting of two forms for the grain velocities: a decaying-exponential tail, which represents grains transported downstream, and a peaked distribution centered at zero velocity, which represents grains that fluctuate due to the turbulent flow but remain in place. Our results suggest that more sophisticated statistical measures may be required to quantify grain motion near the onset of sediment transport, particularly in the presence of turbulence.

arXiv comment9 pages, 7 figures

References in corpus (6)

• Experimental Lagrangian Acceleration Probability Density Function Measurement
• Numerical simulation of turbulent sediment transport, from bed load to saltation
• Erosion of a granular bed driven by laminar fluid flow
• Onset and cessation of motion in hydrodynamically sheared granular beds
• The role of grain dynamics in determining the onset of sediment transport
• Critical shear rate and torque stability condition for a particle resting on a surface in a fluid flow

Cited by in corpus (5)

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• Particle resuspension: challenges and perspectives for future models
• The Cessation Threshold of Nonsuspended Sediment Transport Across Aeolian and Fluvial Environments
• Sediment load determines the shape of rivers
• Competitive dynamics of two erosion patterns around a cylinder