Experimental evidence of statistical ensemble behavior in bed load sediment transport

Siobhan L. Fathel, David Jon Furbish, Mark Schmeeckle

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

A high-resolution data set obtained from high-speed imaging of coarse sand particles transported as bed load allows us to confidently describe the forms and qualities of the ensemble distributions of particle velocities, accelerations, hop distances, and traveltimes. Autocorrelation functions of frame-averaged values (and the decay of these functions) support the idea that the forms of these distributions become time invariant within the 5 s imaging interval. Distributions of streamwise and cross-stream particle velocities are exponential, consistent with previous experiments and theory. Importantly, streamwise particle velocities possess a "light" tail, where the largest velocities are limited by near-bed fluid velocities. Distributions of streamwise and cross-stream particle accelerations are Laplace in form and are centered on zero, consistent with equilibrium transport conditions. The majority of particle hops, measured start to stop, involve short displacements, and streamwise hop distances possess a Weibull distribution. In contrast to previous work, the distribution of traveltimes is exponential, consistent with a fixed temporal disentrainment rate. The Weibull distribution of hop distances is consistent with a decreasing spatial disentrainment rate and is related to the exponential distribution of traveltimes. By taking into account the effects of experimental censorship associated with a finite sampling window, the relationship between streamwise hop distances and traveltimes, Lx-Tpα, likely involves an exponent of α2. These experimental results - an exponential distribution of traveltimes Tp and a Weibull distribution of hop distances Lx with shape parameter k <1 - are consistent with a nonlinear relationship between these quantities with α > 1. Key Points Defined underlying ensemble distributions of characteristic sediment motions Distributions are time-invariant and representative of the ensemble conditions Demonstrated the effects and importance of experimental censorship

Original languageEnglish (US)
Pages (from-to)2298-2317
Number of pages20
JournalJournal of Geophysical Research: Solid Earth
Volume120
Issue number11
DOIs
StatePublished - Nov 1 2015

Fingerprint

sediment transport
Sediment transport
bedload
beds
Weibull distribution
Imaging techniques
Autocorrelation
Sediments
Sand
distribution
Sampling
Fluids
particle acceleration
autocorrelation
sands
Experiments
particle
sediments

Keywords

  • bed load
  • sediment transport
  • stochastic sediment motions

ASJC Scopus subject areas

  • Earth-Surface Processes
  • Geophysics

Cite this

Experimental evidence of statistical ensemble behavior in bed load sediment transport. / Fathel, Siobhan L.; Furbish, David Jon; Schmeeckle, Mark.

In: Journal of Geophysical Research: Solid Earth, Vol. 120, No. 11, 01.11.2015, p. 2298-2317.

Research output: Contribution to journalArticle

@article{a82d040715684e08be02b6d88a8bf49e,
title = "Experimental evidence of statistical ensemble behavior in bed load sediment transport",
abstract = "A high-resolution data set obtained from high-speed imaging of coarse sand particles transported as bed load allows us to confidently describe the forms and qualities of the ensemble distributions of particle velocities, accelerations, hop distances, and traveltimes. Autocorrelation functions of frame-averaged values (and the decay of these functions) support the idea that the forms of these distributions become time invariant within the 5 s imaging interval. Distributions of streamwise and cross-stream particle velocities are exponential, consistent with previous experiments and theory. Importantly, streamwise particle velocities possess a {"}light{"} tail, where the largest velocities are limited by near-bed fluid velocities. Distributions of streamwise and cross-stream particle accelerations are Laplace in form and are centered on zero, consistent with equilibrium transport conditions. The majority of particle hops, measured start to stop, involve short displacements, and streamwise hop distances possess a Weibull distribution. In contrast to previous work, the distribution of traveltimes is exponential, consistent with a fixed temporal disentrainment rate. The Weibull distribution of hop distances is consistent with a decreasing spatial disentrainment rate and is related to the exponential distribution of traveltimes. By taking into account the effects of experimental censorship associated with a finite sampling window, the relationship between streamwise hop distances and traveltimes, Lx-Tpα, likely involves an exponent of α2. These experimental results - an exponential distribution of traveltimes Tp and a Weibull distribution of hop distances Lx with shape parameter k <1 - are consistent with a nonlinear relationship between these quantities with α > 1. Key Points Defined underlying ensemble distributions of characteristic sediment motions Distributions are time-invariant and representative of the ensemble conditions Demonstrated the effects and importance of experimental censorship",
keywords = "bed load, sediment transport, stochastic sediment motions",
author = "Fathel, {Siobhan L.} and Furbish, {David Jon} and Mark Schmeeckle",
year = "2015",
month = "11",
day = "1",
doi = "10.1002/2015JF003552",
language = "English (US)",
volume = "120",
pages = "2298--2317",
journal = "Journal of Geophysical Research: Atmospheres",
issn = "2169-897X",
publisher = "Wiley-Blackwell",
number = "11",

}

TY - JOUR

T1 - Experimental evidence of statistical ensemble behavior in bed load sediment transport

AU - Fathel, Siobhan L.

AU - Furbish, David Jon

AU - Schmeeckle, Mark

PY - 2015/11/1

Y1 - 2015/11/1

N2 - A high-resolution data set obtained from high-speed imaging of coarse sand particles transported as bed load allows us to confidently describe the forms and qualities of the ensemble distributions of particle velocities, accelerations, hop distances, and traveltimes. Autocorrelation functions of frame-averaged values (and the decay of these functions) support the idea that the forms of these distributions become time invariant within the 5 s imaging interval. Distributions of streamwise and cross-stream particle velocities are exponential, consistent with previous experiments and theory. Importantly, streamwise particle velocities possess a "light" tail, where the largest velocities are limited by near-bed fluid velocities. Distributions of streamwise and cross-stream particle accelerations are Laplace in form and are centered on zero, consistent with equilibrium transport conditions. The majority of particle hops, measured start to stop, involve short displacements, and streamwise hop distances possess a Weibull distribution. In contrast to previous work, the distribution of traveltimes is exponential, consistent with a fixed temporal disentrainment rate. The Weibull distribution of hop distances is consistent with a decreasing spatial disentrainment rate and is related to the exponential distribution of traveltimes. By taking into account the effects of experimental censorship associated with a finite sampling window, the relationship between streamwise hop distances and traveltimes, Lx-Tpα, likely involves an exponent of α2. These experimental results - an exponential distribution of traveltimes Tp and a Weibull distribution of hop distances Lx with shape parameter k <1 - are consistent with a nonlinear relationship between these quantities with α > 1. Key Points Defined underlying ensemble distributions of characteristic sediment motions Distributions are time-invariant and representative of the ensemble conditions Demonstrated the effects and importance of experimental censorship

AB - A high-resolution data set obtained from high-speed imaging of coarse sand particles transported as bed load allows us to confidently describe the forms and qualities of the ensemble distributions of particle velocities, accelerations, hop distances, and traveltimes. Autocorrelation functions of frame-averaged values (and the decay of these functions) support the idea that the forms of these distributions become time invariant within the 5 s imaging interval. Distributions of streamwise and cross-stream particle velocities are exponential, consistent with previous experiments and theory. Importantly, streamwise particle velocities possess a "light" tail, where the largest velocities are limited by near-bed fluid velocities. Distributions of streamwise and cross-stream particle accelerations are Laplace in form and are centered on zero, consistent with equilibrium transport conditions. The majority of particle hops, measured start to stop, involve short displacements, and streamwise hop distances possess a Weibull distribution. In contrast to previous work, the distribution of traveltimes is exponential, consistent with a fixed temporal disentrainment rate. The Weibull distribution of hop distances is consistent with a decreasing spatial disentrainment rate and is related to the exponential distribution of traveltimes. By taking into account the effects of experimental censorship associated with a finite sampling window, the relationship between streamwise hop distances and traveltimes, Lx-Tpα, likely involves an exponent of α2. These experimental results - an exponential distribution of traveltimes Tp and a Weibull distribution of hop distances Lx with shape parameter k <1 - are consistent with a nonlinear relationship between these quantities with α > 1. Key Points Defined underlying ensemble distributions of characteristic sediment motions Distributions are time-invariant and representative of the ensemble conditions Demonstrated the effects and importance of experimental censorship

KW - bed load

KW - sediment transport

KW - stochastic sediment motions

UR - http://www.scopus.com/inward/record.url?scp=84954363223&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84954363223&partnerID=8YFLogxK

U2 - 10.1002/2015JF003552

DO - 10.1002/2015JF003552

M3 - Article

VL - 120

SP - 2298

EP - 2317

JO - Journal of Geophysical Research: Atmospheres

JF - Journal of Geophysical Research: Atmospheres

SN - 2169-897X

IS - 11

ER -