Effect of particle shape on settling velocity of microplastic particles

The aim of this thesis is to investigate the effect of particle shape on the settling velocity of microplastic (MP) particles through laboratory experiments. For this purpose, different types of MPs with various regular shapes were selected based on literature, including polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), resin, polymethyl methacrylate (PMMA), polyamide 6 (PA-6), and polystyrene (PS). The regular shapes examined are sphere (S), box-shaped prism (BSP), cube, cylinder, C-shape, half-cylinder (HC), elliptical cylinder (EC), and disc (D). To analyze the influence of shape on particle settling behavior, drag coefficient (Cd) versus Reynolds number (Re) charts, comparisons of experimental Cd values with theoretical correlations, and settling velocity versus Cd charts were generated and discussed. The experimental findings reveal that particle shape significantly affects settling velocity and drag characteristics. However, material type and surface roughness also play critical roles, as particles with identical shapes but different polymer types exhibit varying settling dynamics. These results underscore the complexity of microplastic behavior in aquatic environments. It is recommended that future studies focus on the influence of surface roughness to better understand its impact on particle settling.