What the study found
The study found that the final shape of spreading droplets of yield-stress fluids depends on both gravity and yield stress. In microgravity, the researchers could separate the influence of surface tension from yield stress on those final shapes.
Why the authors say this matters
The authors conclude that microgravity makes it possible to vary two key dimensionless numbers independently: the Bond number, which compares gravity and surface tension, and the plastocapillary number, which compares yield stress and surface tension. The study suggests this helps disentangle how surface tension and yield stress shape these droplets.
What the researchers tested
The researchers studied droplets of yield-stress fluids in both microgravity experiments in a drop tower and experiments under terrestrial gravity. The droplets were deposited on a thin film of the same material, which mimicked a fully wetting surface and allowed tests of scaling laws from the thin-film equation for viscoplastic fluids. They also used simulations with a viscoelastic model that included shear-thinning.
What worked and what didn't
The simulations showed good agreement with the experiments for droplet shapes. The abstract also notes that possible deviations were discussed for conditions with non-negligible elastic effects and large plastocapillary numbers, meaning large yield stress.
What to keep in mind
The available summary does not provide detailed numerical results or a full accounting of limitations. It also only mentions possible deviations in regimes with stronger elastic effects and large plastocapillary numbers, without giving further details.
Key points
- Final droplet shape depends on both gravity and yield stress.
- Microgravity allowed the researchers to vary the Bond number and plastocapillary number independently.
- Droplets were placed on a thin film of the same material to mimic a fully wetting surface.
- Simulations with a viscoelastic, shear-thinning model agreed well with the measured droplet shapes.
- Possible deviations were discussed for regimes with stronger elastic effects and large yield stress.
Disclosure
- Research title:
- Gravity changes final shapes of spreading yield-stress droplets
- Authors:
- Linnea Heitmeier, Olfa D’Angelo, Maziyar Jalaal, Thomas Voigtmann
- Institutions:
- Amsterdam University of Applied Sciences, Amsterdam University of Applied Sciences, Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR), Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR), Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR), Heinrich Heine University Düsseldorf, Heinrich Heine University Düsseldorf, National Higher French Institute of Aeronautics and Space
- Publication date:
- 2026-04-21
- DOI:
- 10.1122/8.0001083
- OpenAlex record:
- View
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