Lagrangian statistics of bed-load particle transport from experiments with a long measurement domain

Bed-load particle hop data may suffer from censorship due to using a short observation window, which results in underestimated mean values of the key physical quantities. By contrast, an appropriate design of an experimental campaign may considerably reduce the biasing effect of censorship. This study presents an analysis of earlier experiments with visualization of bed-load particles, where a long observation window was achieved using multiple cameras. The tracks (full paths along the observation window) of the bed-load particles were obtained, then particle hops (motions from entrainment to disentrainment) were extracted. The present data samples were indeed very limitedly affected by censorship. The mean values of the hop properties for the present dataset were compared with the data available in the literature. A very satisfactory agreement was achieved between the present data and those from experimental campaigns where either censorship was avoided or its effects were appropriately corrected, depicting a completely different trend from that for other works where censorship effects were presumably overlooked. Preliminary statistics are presented to demonstrate the richness of the data set. The use of a long observation window thus represents a new paradigm to be used as a best-practice in experimental investigations of bed-load particle transport.