Adding particle collisions to the formation of asteroids and Kuiper belt objects via streaming instabilities
(2012) In Astronomy & Astrophysics 537. Abstract
 Modelling the formation of superkmsized planetesimals by gravitational collapse of regions overdense in small particles requires numerical algorithms capable of handling simultaneously hydrodynamics, particle dynamics and particle collisions. While the initial phases of radial contraction are dictated by drag forces and gravity, particle collisions become gradually more significant as filaments contract beyond Roche density. Here we present a new numerical algorithm for treating momentum and energy exchange in collisions between numerical superparticles representing a high number of physical particles. We adopt a Monte Carlo approach where superparticle pairs in a grid cell collide statistically on the physical collision timescale.... (More)
 Modelling the formation of superkmsized planetesimals by gravitational collapse of regions overdense in small particles requires numerical algorithms capable of handling simultaneously hydrodynamics, particle dynamics and particle collisions. While the initial phases of radial contraction are dictated by drag forces and gravity, particle collisions become gradually more significant as filaments contract beyond Roche density. Here we present a new numerical algorithm for treating momentum and energy exchange in collisions between numerical superparticles representing a high number of physical particles. We adopt a Monte Carlo approach where superparticle pairs in a grid cell collide statistically on the physical collision timescale. Collisions occur by enlarging particles until they touch and solving for the collision outcome, accounting for energy dissipation in inelastic collisions. We demonstrate that superparticle collisions can be consistently implemented at a modest computational cost. In protoplanetary disc turbulence driven by the streaming instability, we argue that the relative Keplerian shear velocity should be subtracted during the collision calculation. If it is not subtracted, density inhomogeneities are too rapidly diffused away, as bloated particles exaggerate collision speeds. Local particle densities reach several thousand times the midplane gas density. We find efficient formation of gravitationally bound clumps, with a range of masses corresponding to contracted radii from 100 to 400 km when applied to the asteroid belt and 150 to 730 km when applied to the Kuiper belt, extrapolated using a constant selfgravity parameter. The smaller planetesimals are not observed at low resolution, but the masses of the largest planetesimals are relatively independent of resolution and treatment of collisions. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/record/2515917
 author
 Johansen, Anders ^{LU} ; Youdin, A. N. and Lithwick, Y.
 organization
 publishing date
 2012
 type
 Contribution to journal
 publication status
 published
 subject
 keywords
 asteroids: general, methods: numerical, minor planets, planets and satellites: formation, hydrodynamics, turbulence, protoplanetary disks
 in
 Astronomy & Astrophysics
 volume
 537
 publisher
 EDP Sciences
 external identifiers

 wos:000300416800125
 scopus:84855941794
 ISSN
 00046361
 DOI
 10.1051/00046361/201117701
 language
 English
 LU publication?
 yes
 id
 a4041f06681a45b5b041c8be1a7a08e4 (old id 2515917)
 date added to LUP
 20120508 13:23:54
 date last changed
 20180311 04:00:32
@article{a4041f06681a45b5b041c8be1a7a08e4, abstract = {Modelling the formation of superkmsized planetesimals by gravitational collapse of regions overdense in small particles requires numerical algorithms capable of handling simultaneously hydrodynamics, particle dynamics and particle collisions. While the initial phases of radial contraction are dictated by drag forces and gravity, particle collisions become gradually more significant as filaments contract beyond Roche density. Here we present a new numerical algorithm for treating momentum and energy exchange in collisions between numerical superparticles representing a high number of physical particles. We adopt a Monte Carlo approach where superparticle pairs in a grid cell collide statistically on the physical collision timescale. Collisions occur by enlarging particles until they touch and solving for the collision outcome, accounting for energy dissipation in inelastic collisions. We demonstrate that superparticle collisions can be consistently implemented at a modest computational cost. In protoplanetary disc turbulence driven by the streaming instability, we argue that the relative Keplerian shear velocity should be subtracted during the collision calculation. If it is not subtracted, density inhomogeneities are too rapidly diffused away, as bloated particles exaggerate collision speeds. Local particle densities reach several thousand times the midplane gas density. We find efficient formation of gravitationally bound clumps, with a range of masses corresponding to contracted radii from 100 to 400 km when applied to the asteroid belt and 150 to 730 km when applied to the Kuiper belt, extrapolated using a constant selfgravity parameter. The smaller planetesimals are not observed at low resolution, but the masses of the largest planetesimals are relatively independent of resolution and treatment of collisions.}, articleno = {A125}, author = {Johansen, Anders and Youdin, A. N. and Lithwick, Y.}, issn = {00046361}, keyword = {asteroids: general,methods: numerical,minor planets,planets and satellites: formation,hydrodynamics,turbulence,protoplanetary disks}, language = {eng}, publisher = {EDP Sciences}, series = {Astronomy & Astrophysics}, title = {Adding particle collisions to the formation of asteroids and Kuiper belt objects via streaming instabilities}, url = {http://dx.doi.org/10.1051/00046361/201117701}, volume = {537}, year = {2012}, }