Aerodynamic and Mechanical Properties of Dust Aggregates in Low-Gravity Environments

Understanding the intricate dynamics of gas-dust interactions within protoplanetary disks is crucial for unraveling the mysteries of planetary system formation. We introduce TEMPus VoLA (Timed Epstien Multi-pressure vessel at Low Accelerations), an experimental setup designed to investigate particle dynamics and rarefied gas behavior in microgravity (Capelo et al. 2022 https://doi.org/10.1063/5.0087030). Figure 1 shows the experimental setup in flight configuration, together with a rendering of the multiple pressure vessels containing low-pressure gas and dust analogue materials.  

Figure 1 (Reproduced from Capelo et al 2022). Left: TEMPusVoLA in flight configuration aboard Air Zero-G. Right: Multiple pressure vessels containing rarified gas and dust particle analog. Each chamber is designated to study a particular process: Shear flow, permeability, and drag forces on aggregates. 

 

Through multiple dedicated experiments, we explore the effects of collective particle-gas interaction on pressure gradients (permeability), aerodynamic drag coefficients and mechanical properties of dust aggregates, and the onset of turbulence in shear flows. Figure 2 shows an example of a periodic velocity field developing in the shear flow chamber, where dust is injected as a stream in the flow of gas at vaccum pressure. We interpret the velocity field to indicate the onset of a Kelvin-Helmholtz like instability, generated for the first time with dust as the dense phase in pure molecular flow. 

 

Figure 2 (Reproduced from Capelo et al. 2022). Particle-velocity in the stream-wise direction of the shear flow chamber, derived using particle image velocimetry.  The particle velocities are not constant, but rather oscilate.

 

Our findings, gleaned from multiple parabolic flight campaigns, support a better understanding of dust transport and dynamics in planet-forming discs and also have implications for understanding phenomena like dust emission from cometary nuclei. The presented framework offers a valuable tool for validating models and numerical simulations of collective dust particle aerodynamics in low-gravity environments.