Granular mechanics simulations of collisions between chondritic aggregates

Abstract

Context. Collisions of dust aggregates are relevant for the evolution of protoplanetary disks. Aims. While in the past interest focused on aggregates composed of monodisperse grains, here we study the collision of chondritic aggregates, in which – besides a majority of dust grains – larger chondrules are embedded. Methods. We use granular-mechanics simulations to study collisions of chondritic aggregates. Results. Low-velocity collisions lead to pancake-shaped deformations of the fused cluster accompanied by a compaction of the dust grains. Higher collision velocities fragment the aggregates. While some chondrules are almost laid bare after the collision, we find that the largest fragments typically contain chondrules; large fragments thus capture chondrules. Grain compaction is accompanied by an increase in grain – chondrule contacts and is maximum for intermediate velocities, just before aggregates start fragmenting. Conclusions. The presence of chondrules considerably influences the fragmentation behavior of dust aggregates.

Impacts of Viscous Dissipation on Collisional Growth and Fragmentation of Dust Aggregates

“…The collisional behavior of dust aggregates has been reported in a large number of studies based on both laboratory experiments (e.g., Blum & Wurm 2008;Güttler et al 2010;Shimaki & Arakawa 2012;Brisset et al 2016Brisset et al , 2017Schräpler et al 2018Schräpler et al , 2022Fritscher & Teiser 2021) and numerical simulations (e.g., Wada et al 2007Wada et al , 2008Wada et al , 2009Wada et al , 2013Paszun & Dominik 2009;Seizinger et al 2013;Sirono & Ueno 2017;Umstätter & Urbassek 2020, 2021aHasegawa et al 2021;Sirono & Kudo 2021). It is known that the threshold collision velocity for the fragmentation of dust aggregates, v fra , depends on material properties of constituent particles.…”

“…Most of numerical simulations of collisions between dust aggregates did not include the viscous dissipation force (e.g., Dominik & Tielens 1997;Wada et al 2007Wada et al , 2008Wada et al , 2009Hasegawa et al 2021). Although a small number of studies (e.g., Seizinger et al 2013;Umstätter & Urbassek 2021a, 2021b introduced the viscous dissipation force to their numerical simulations of collisions between dust aggregates, the dependence of v fra on the strength of viscous dissipation force is still poorly understood. For head-on collisions between equal-mass dust aggregates, Umstätter & Urbassek (2021b) reported that the threshold velocity increases with increasing the strength of viscous dissipation force; however, when we consider oblique collisions, whether the viscous dissipation helps the collisional growth of dust aggregates is still unclear.…”

Fine-grained rim formation via kinetic dust aggregation in shock waves around evaporating icy planetesimals

“…Therefore, we must give an explanation for the co-existence of rimmed and unrimmed chondrules in the context of FGR formation. Several mechanisms were proposed so far: Tomeoka & Ohnishi (2010) claimed that unrimmed chondrules have lost FGRs during the brecciation process on their parent bodies, whereas Umstätter & Urbassek (2021) proposed that unrimmed chondrules were formed via collisional fragmentation of chondritic aggregates in the solar nebula.…”

Dependence of the initial internal structure of chondrule rim on dust size distribution

“…However, much lower φ agg does not necessarily mean much lower φ rim because porous aggregates can be compressed when they accrete onto chondrules. Further more, compound aggregates (Arakawa, 2017;Matsumoto et al, 2019) composed of rimmed chondrules and matrix aggregates might suffer ejection of chondrules through collisions (Arakawa, 2017;Umstätter and Urbassek, 2021). This mechanism can be one of the causes of unrimmed chondrules (e.g Simon et al, 2018).…”