We use cookies to ensure that we give you the best experience on our website. By continuing to browse this repository, you give consent for essential cookies to be used. You can read more about our Privacy and Cookie Policy.

Durham Research Online
You are in:

Planetary giant impacts : convergence of high-resolution simulations using efficient spherical initial conditions and SWIFT.

Kegerreis, J.A. and Eke, V.R. and Gonnet, P. and Korycansky, D.G. and Massey, R.J. and Schaller, M. and Teodoro, L.F.A. (2019) 'Planetary giant impacts : convergence of high-resolution simulations using efficient spherical initial conditions and SWIFT.', Monthly notices of the Royal Astronomical Society., 487 (4). pp. 5029-5040.


We perform simulations of giant impacts onto the young Uranus using smoothed particle hydrodynamics (SPH) with over 100 million particles. This 100–1000 × improvement in particle number reveals that simulations with below 107 particles fail to converge on even bulk properties like the post-impact rotation period, or on the detailed erosion of the atmosphere. Higher resolutions appear to determine these large-scale results reliably, but even 108 particles may not be sufficient to study the detailed composition of the debris – finding that almost an order of magnitude more rock is ejected beyond the Roche radius than with 105 particles. We present two software developments that enable this increase in the feasible number of particles. First, we present an algorithm to place any number of particles in a spherical shell such that they all have an SPH density within 1% of the desired value. Particles in model planets built from these nested shells have a root-mean-squared velocity below 1% of the escape speed, which avoids the need for long precursor simulations to produce relaxed initial conditions. Second, we develop the hydrodynamics code SWIFT for planetary simulations. SWIFT uses task-based parallelism and other modern algorithmic approaches to take full advantage of contemporary supercomputer architectures. Both the particle placement code and SWIFT are publicly released.

Item Type:Article
Full text:(AM) Accepted Manuscript
Download PDF
Full text:(VoR) Version of Record
Download PDF
Publisher Web site:
Publisher statement:© 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.
Date accepted:05 June 2019
Date deposited:18 June 2019
Date of first online publication:10 June 2019
Date first made open access:18 June 2019

Save or Share this output

Look up in GoogleScholar