Sand particle kinematics under different transport conditions

Abstract

The kinematics of sediment particles is investigated by non-intrusive imaging to provide a stochastic description of bedload transport in conditions near the threshold of motion. In particular, we focus on the cyclic transition between motion and rest regimes to quantify the statistical properties of the particles waiting times, inferred to be responsible for anomalous diffusion, and so far elusive. The probability distributions of the particle step time and step length, streamwise and spanwise velocity, acceleration, and waiting time are quantified experimentally. Results suggest that variables associated with the particle step motion are thin-tailed distributed while the waiting times exhibit a power law distribution. The experimental results shown here, under five different transport conditions, describe grain scale kinematics and dynamics at increasing shear stress and represent a benchmark dataset for the stochastic modeling of bedload transport.