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Journal Articles Journal of Geophysical Research: Earth Surface Year : 2014

Journal of Geophysical Research: Earth Surface

Hongbo Ma
  • Function : Author
François Mettra
  • Function : Author
Christophe Ancey
  • Function : Author
  • PersonId : 1045594


This article examines the spatial dynamics of bed load particles in water. We focus particularly on the fluctuations of particle activity, which is defined as the number of moving particles per unit bed length. Based on a stochastic model recently proposed by Ancey and Heyman (2014), we derive the second moment of particle activity analytically, that is, the spatial correlation functions of particle activity. From these expressions, we show that large moving particle clusters can develop spatially. Also, we provide evidence that fluctuations of particle activity are scale dependent. Two characteristic lengths emerge from the model: a saturation length sat describing the length needed for a perturbation in particle activity to relax to the homogeneous solution and a correlation length c describing the typical size of moving particle clusters. A dimensionless Péclet number can also be defined according to the transport model. Three different experimental data sets are used to test the theoretical results. We show that the stochastic model describes spatial patterns of particle activity well at all scales. In particular, we show that c and sat may be relatively large compared to typical scales encountered in bed load experiments (grain diameter, water depth, bed form wavelength, flume length, etc.) suggesting that the spatial fluctuations of particle activity have a nonnegligible impact on the average transport process.

Dates and versions

hal-03018850 , version 1 (23-11-2020)



Joris Heyman, Hongbo Ma, François Mettra, Christophe Ancey. Journal of Geophysical Research: Earth Surface. Journal of Geophysical Research: Earth Surface, 2014, ⟨10.1002/2013JF003003⟩. ⟨hal-03018850⟩
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