The coupled effects between sediment and fluid in suspension layer during flow reversal under symmetric oscillatory sheet flow

Sediment transport under oscillatory sheet flow conditions provide an important example of strongly-coupled particle/turbulence interaction within an important practical flow. It has long been observed that concentration maxima occur at flow reversals, but they have not been well-captured in existing numerical simulations/models. A stereo PIV/PTV based multi-camera imaging method has been recently developed, enabling particle-resolved concurrent two-phase measurement in the middle of a typical sheet flow facility, with a thick mobile bed composed of well-sorted sediment particles (D₅₀=250μm, ρ_s=2.5g/cm³). Time-resolved highspeed recordings were conducted during flow reversals in a symmetric sinusoidal oscillatory sheet flow, with a period of 5s and excursion length of 0.80m. Within the suspended layer up to a volumetric fraction of close to 1%, time-series of 2D3C fluid velocities resolved down to sediment-scale were computed. In addition to each velocity field, instantaneous 3D sediment particle locations were reconstructed and tracked in consecutive frames to form trajectories. Derived statistics, such as sediment concentration, fluid and sediment kinematics and associated fluctuations, slip velocities etc. will be reported.