Spreading droplets of yield-stress fluids with and without gravity

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Main Authors: Heitmeier, Linnea, D'Angelo, Olfa, Jalaal, Maziyar, Voigtmann, Thomas
Format: Preprint
Published: 2025
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author Heitmeier, Linnea
D'Angelo, Olfa
Jalaal, Maziyar
Voigtmann, Thomas
author_facet Heitmeier, Linnea
D'Angelo, Olfa
Jalaal, Maziyar
Voigtmann, Thomas
contents We investigate the effect of gravity on the spreading of droplets of yield stress fluids, by performing both microgravity experiments (in a drop tower) and experiments under terrestrial gravity. We investigate the dependence of the final droplet shape on yield stress and gravity. Droplets are deposited on a thin film of the same material, allowing to directly test scaling laws derived from the thin-film equation for viscoplastic fluids. Microgravity conditions allow to vary independently the two relevant dimensionless numbers, the Bond number, B, and the plastocapillary number, J, and thus to disentangle the influence of surface tension from that of the yield stress on the droplet shapes. Simulations using a visco-elastic model with shear thinning complement the experiments and show good agreement regarding the droplet shapes. Possible deviations arising in the regime of non-negligible elastic effects and large plastocapillary numbers (large yield stress) are discussed.
format Preprint
id arxiv_https___arxiv_org_abs_2507_04379
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Spreading droplets of yield-stress fluids with and without gravity
Heitmeier, Linnea
D'Angelo, Olfa
Jalaal, Maziyar
Voigtmann, Thomas
Fluid Dynamics
We investigate the effect of gravity on the spreading of droplets of yield stress fluids, by performing both microgravity experiments (in a drop tower) and experiments under terrestrial gravity. We investigate the dependence of the final droplet shape on yield stress and gravity. Droplets are deposited on a thin film of the same material, allowing to directly test scaling laws derived from the thin-film equation for viscoplastic fluids. Microgravity conditions allow to vary independently the two relevant dimensionless numbers, the Bond number, B, and the plastocapillary number, J, and thus to disentangle the influence of surface tension from that of the yield stress on the droplet shapes. Simulations using a visco-elastic model with shear thinning complement the experiments and show good agreement regarding the droplet shapes. Possible deviations arising in the regime of non-negligible elastic effects and large plastocapillary numbers (large yield stress) are discussed.
title Spreading droplets of yield-stress fluids with and without gravity
topic Fluid Dynamics
url https://arxiv.org/abs/2507.04379