Influence of engineered roughness microstructures on adhesion and turbulent resuspension of microparticles


Influence of engineered roughness microstructures on adhesion and turbulent resuspension of microparticles

Banari, A.; Graebe, K.; Rudolph, M.; Mohseni, E.; Lorenz, P.; Zimmer, K.; Hübner, R.; Henry, C.; Bossy, M.; Hampel, U.; Lecrivain, G.

From microplastics resuspending into the atmosphere to earth particles left behind during extraterrestrial explorations, the resuspension of microparticles by a turbulent gas flow occurs in many natural and industrial systems. Wall surfaces, onto which particles initially adhere, are rarely smooth and this surface roughness affects their resuspension. Available experimental data on particle resuspension have been obtained with substrates, whose surfaces are either unaltered or manually abraded with, for instance, sand blasting. In these experiments, the roughness elements span a wide size range and are in-homogeneously distributed in space. Surface functionalization is a modern technique allowing the precise fabrication of a wall surface with well-characterized microstructures, hence reducing the asperity randomness associated with conventional abrasion techniques. Taking advantage of surface functionalization, we present here a new set of reference data, where the wall asperities are represented by a structured arrangement of micropillars and microcubes. Adhesion force measurements and particle remaining fraction against gas velocity, at Reynolds number up to 8000, are reported for one reference and two artificially roughened substrates. Laboratory measurements show that the microasperities have little to moderate effect on the mean adhesion force and the threshold velocity, at which half of the 100-µm particles resuspend. The standard deviations are, however, significantly affected. The presented results will primary contribute to the improvement of resuspension models, which until now rely on a simplified representation of the surface roughness elements. The presented measurements are highly compatible with such models, which involve elementary roughness features, such as hemispherical asperities superimposed with a flat plate.

Keywords: Particle resuspension; Adhesion force measurement; Turbulent gas flow; Surface functionalization; Surface roughness

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