Impact of inertia on flow-induced particle motion in laminar shear flow

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Flow induced detachment and motion of solid particles on a fixed substrate or granular bed is of fundamental relevance in numerous natural and industrial systems. As examples sediment and granular transport in conveying, filtration, fractionation, natural watercourses and piping systems, particle transport in the respiratory system, and the cleaning of surfaces may be mentioned. In microfluidics, spherical particles are progressively used as information carrier or for actuators like valves or pumps. Therefore, an important precondition is the controlled positioning of particles. While the motion of single particles on smooth walls is quite well understood, this does not hold for structured surfaces and granular beds. This is mainly because the material transport and especially the particle motion and its onset has been studied in the numerous studies exclusively in disordered sediment layers and has been tried to describe using not well-defined parameters in the models. Recently, we could provide a quantitative deterministic description of the motion and its onset in the creeping-flow limit without harking back to data fitting. It is based on well-defined experiments with structured substrates together with numerical calculations of the acting flow-induced forces and torques. The impact of inertia on the incipient motion remains an open question. It is expected to have far-reaching implications ranging from the impact on the critical Shields number for the onset of motion and the type of bifurcation to the dependence on the duration of the shear load and to resonance with the substrate topography. In the proposed project, we intend to answer these questions.