Parameter optimization for image-based measurement of bed-load transport in pressurized closed channel flow

Image-based measurement of bed-load transport involves a set of parameters, e.g. sample size, sampling duration, sampling area, and the time interval between two frames in an image pair. These parameters are important to guarantee reliable quantification of bed-load motion which is temporally intermittent and spatially stochastic. We conducted experiments in a closed channel and investigated the influence of parameter selection on the measurement of probability in motion, moving speed and transport rate. Under the experimental conditions, it can be revealed that the statistical average results are convergent only when the sample size is no less than 5000, sampling duration is no shorter than 100s and the sampling area is more than 400 times the square of grain size. Meanwhile, the velocity and sediment flux decrease with increased time interval, but the probability increases almost linearly with the time interval. The present findings provide useful information to facilitate parameter optimization for image-based measurement of bed-load transport.