Experimental evidence for granular shear-flow instability in the Epstein regime
Abstract
Stability analysis of two-fluid protoplanetary disc models has enriched our understanding of how solids can grow into larger bodies called planetesimals. Dust particles entrained in a gas stream modify the flow, creating shear layers prone to instability. In such environments, drag occurs in the free-molecular (Epstein) regime. Recreating these two-phase flows on Earth is difficult due to gravity-driven buoyancy. Here, we use particle image velocimetry to study a low-pressure dust-gas mixture at Knudsen numbers up to 10 in microgravity. We observe a granular shear flow instability, characterized by a periodic velocity field, which can be modeled to first order as a Kelvin-Helmholtz (KH) instability. This behavior resembles a Kelvin-Helmholtz instability and provides a benchmark for two-fluid theories relevant to planet formation.
Keywords
Cite
@article{arxiv.2603.15810,
title = {Experimental evidence for granular shear-flow instability in the Epstein regime},
author = {Holly L. Capelo and Jean-David Bodénan and Martin Jutzi and Jonas Kühn and Clément Surville and Lucio Mayer and Maria Schönbächler and Yann Alibert and Nicolas Thomas and Antoine Pommerol},
journal= {arXiv preprint arXiv:2603.15810},
year = {2026}
}
Comments
9 pages, 5 figures