Can terminal settling velocity and drag of natural particles in water ever be predicted accurately?

Abstract. Natural particles are frequently applied in drinking water treatment processes fixed bed reactors, fluidised and sedimentation to clarify concentrate solids. When settle, it has been found that, terms of hydraulics, natural behave differently when compared perfectly round spheres. To estimate the terminal settling velocity single solid a liquid system, comprehensive collection equations is available. For spheres, can be calculated quite accurately. However, for naturally polydisperse non-spherical particles, experimentally measured velocities individual show considerable spread from average values. This work aims analyse explain different causes this spread. end, experiments were conducted quiescent fluid with varying density, size, shape. experiments, opaque transparent spherical monodisperse glass beads selected. In study, we also examined drinking-water-related like calcite pellets crushed seeding material grains, which both softening. Polydisperse sieved separated acquire more uniformly dispersed samples. addition, wide variety grains densities, sizes, shapes investigated their behaviour. The derived drag coefficient was well-known models such as one Brown Lawler (2003). A sensitivity analysis showed that caused, lesser extent, by variations properties, measurement errors, wall effects. specific particle path trajectory instabilities, distinctive multi-particle behaviour caused slightly larger degree contrast, greater shape, orientation. robust process designs adequate optimisation fluidisation granules, therefore crucial take into consideration influence using predictive