Smart Sediment Particle: A novel approach to investigating fluvial bed entrainment using instrumented sensors

Abstract

The Smart Sediment Particle (SSP) instrumented with multiple sensors to obtain tri-axial linear accelerations is used for studying the mechanism of coarse grain entrainment. Three bed arrangements are tested to examine their influences on entrainment processes and the threshold force and impulse conditions. The SSP shows satisfactory precision to capture the imperceptible movement tendencies immediately (e.g., 0.15 s) after the dislodgement. The experimental results show that bed packing can significantly affect the particle's entrainment threshold and the path of movement. Lateral movement is predominant for some cases because the entrainment path is based on the least work done by the flow, even if the direction is not aligned with the flow. The concept of effective protrusion height is proposed to quantify the effect of local bed arrangement on entrainment. The mean velocity field around the SSP is also measured together with the acceleration data. The mean threshold velocity and resultant impulse show consistent dependence on the bed arrangement. In general, the SSP shows a good prospect of being used to study small-scale entrainment mechanism.