Author(s): Luis Mendes; Federica Antico; Duarte Carona; Rui Aleixo; Rui M. L. Ferreira
Linked Author(s): Rui M.L. Ferreira
Keywords: Bedload measurements; Particle Tracking Velocimetry; Impact method; Particle counter
Abstract: The morphology of loose bed channels depends on gradients of bedload fluxes. The latter are difficult to determine even in controlled laboratory conditions. In this paper two methods have been used to obtain bedload discharge measurements, a pressure-based impact method and two PTV (Particle Tracking technique) image processing based methods. These methods are capable of providing highly resolved bedload flux estimations. The implemented PTV techniques also provide sediment velocities and trajectories. The methods were tested in laboratory conditions. Experimental conditions comprised recirculation of glass beads in uniform flows. Manual counting for a limited period provided the reference data to compare with the image processing and the pressure-based impact method. Each device has its own strengths and weaknesses. The pressure-based impact method cannot provide sub-particle resolution but is able to capture very long time series. The image processing method is unsuitable for very long periods, because of prohibitive processing times, but is able to define bedload fluxes at scales much smaller than particle size. The methods complement each other, allowing for a higher dynamic range of bedload measurements.