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.

9 pages, 5 figures

References in corpus (17)

• Streaming Instabilities in Protoplanetary Disks
• On the drag of freely falling non-spherical particles
• Dynamics of Solids in the Midplane of Protoplanetary Disks: Implications for Planetesimal Formation
• Formation of planetary systems by pebble accretion and migration: How the radial pebble flux determines a terrestrial-planet or super-Earth growth mode
• Dust sedimentation and self-sustained Kelvin-Helmholtz turbulence in protoplanetary disk mid-planes. I. Radially symmetric simulations
• On linear dust-gas streaming instabilities in protoplanetary discs
• Kinematics of the CO Gas in the Inner Regions of the TW Hya Disk
• Pebble-driven Planet Formation around Very Low-mass Stars and Brown Dwarfs
• Resonant drag instability of grains streaming in fluids
• The effect of the Coriolis force on Kelvin-Helmholtz-driven mixing in protoplanetary disks
• The Resonant Drag Instability (RDI): Acoustic Modes
• Induced Turbulence and the Density Structure of the Dust Layer in a Protoplanetary Disk
• Spontaneous concentrations of solids through two-way drag forces between gas and sedimenting particles
• Dust-vortex instability in the regime of well-coupled grains
• Dense Particle Clouds in Laboratory Experiments in Context of Drafting and Streaming Instability
• Observation of aerodynamic instability in the flow of a particle stream in a dilute gas
• TEMPus VoLA: the Timed Epstein Multi-pressure Vessel at Low Accelerations