Response of microplastic particles to turbulent flow: An experimental study

Particle movement in turbulent flow is complex within the domain of multiphase flow dynamics. Hydrodynamics of microplastics (MPs), as emerging contaminants, have drawn significant attention due to their adverse ecosystem health impacts. MPs exhibit a broad spectrum of sizes, ranging from sub-millimeter to micron-scale dimensions, and shapes from beads to fibers. As a result, MPs’ mobility and hydrodynamics are complex. For instance, due to their variability, MPs can possess a wide range of particle Reynolds numbers, which can fall into the Stokesian regime all the way to non-linear Newtonian dynamics. In this study, to understand the response of MPs to turbulent flow in aquatic settings, an open channel flume is utilized. This flume facilitated the generation of controlled turbulence, which was then examined using a stereo particle image velocimetry (PIV) system. Within the confines of this regulated environment, MP particles were introduced into the field of view, and their movement and paths were monitored with a particle tracking velocimetry (PTV) system. This paper presents experimental investigation of the complex movement of MPs, focusing on microbeads and microfibers, in turbulent flows. This study examines the movement and distribution of MPs under turbulent flow conditions using the PTV experimental setup, formulating the difference in behavior between fibers and beads of the same equivalent spherical diameter. The outcomes derived from these tests provide insights into the intricate mechanisms of MP transportation and potential ramifications on river ecosystems.