Dense Particle Clouds in Laboratory Experiments in Context of Drafting and Streaming Instability

Abstract

The streaming instability, as an example of instabilities driven by particle feedback on a gas flow, has been proven to have a major role in controlling the formation of planetesimals. Here, we present experiments to approach this situation in the laboratory for particles in the Knudsen flow regime. In these experiments, we observe a particle cloud trapped for about 30 s in a rotating system under Earth's gravity. For average dust-to-gas ratios up to 0.08, particles behave like individual test particles. Their sedimentation speed is identical to that of a single free-falling particle, even in locally denser regions. However, for higher dust-to-gas ratios, the motion of particles becomes sensitive to clumping. Particles in locally denser regions now sediment faster. Their sedimentation speed then depends linearly on the overall dust-to-gas ratio. This clearly shows a transition from tracerlike behavior to collective behavior. Beyond these findings, these types of experiments can now be used as a gauge to test the particle feedback models in astrophysical hydrocodes which are currently used for numerical simulations of streaming instabilities.

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• Experimental study of clusters in dense granular gas and implications for the particle stopping time in protoplanetary disks
• Constraining giant planet formation with synthetic ALMA images of the Solar System's natal protoplanetary disk
• Laboratory Experiments on the Motion of Dense Dust Clouds
• Accretion of eroding pebbles and planetesimals in planetary envelopes
• Ionizing Protoplanetary Disks in Pebble Collisions
• The Dissolution of Planetesimals in Electrostatic Fields
• Experimental evidence for granular shear-flow instability in the Epstein regime