Modeling dust dynamics in OpenGadget3

I. SPH implementation of the One-Fluid model

¹ University Observatory, Faculty of Physics, Ludwig-Maximilians-Universität München, Scheinerstr. 1, 81679 Munich, Germany
² Exzellenzcluster ORIGINS, Boltzmannstr. 2, 85748 Garching, Germany
³ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Straße 1, 85741 Garching, Germany
⁴ Hochschule für angewandte Wissenschaften München, Lothstraße 34, 80335 München, Germany

^★ Corresponding author: giovanni.tedeschi@campus.lmu.de

Received: 7 February 2025
Accepted: 29 October 2025

Abstract

Context. Dust dynamics plays a critical role in astrophysical processes and has been modeled in hydrodynamical simulations using various approaches. Among particle-based methods like Smoothed Particle Hydrodynamics (SPH), the One-Fluid model has proven to be highly effective for simulating gas-dust mixtures.

Aims. This study presents the implementation of the One-Fluid model in OpenGadget3, introducing improvements to the original formulation. These enhancements include time-dependent artificial viscosity and conductivity, as well as a novel treatment of dust diffusion using a pressure-like term.

Methods. The improved model is tested using a suite of dust dynamics benchmark problems: DUSTYBOX, DUSTYWAVE, and DUSTYSHOCK, with the latter extended to multidimensional scenarios, as well as a dusty Sedov-Taylor blast wave. Additional tests include simulations of Cold Keplerian Disks, dusty protoplanetary disks, and Kelvin–Helmholtz instabilities to evaluate the model’s robustness in more complex flows.

Results. The implementation successfully passes all standard benchmark tests. It demonstrates stability and accuracy in both simple and complex simulations. The new diffusion term improves the handling of flows with large dust-to-gas ratios and low drag coefficients, although limitations of the One-Fluid model in these regimes remain.

Conclusions. The enhanced One-Fluid model is a reliable and robust tool for simulating dust dynamics in OpenGadget3. While it retains some limitations inherent to the original formulation, the introduced improvements expand its applicability and address some challenges in gas-dust dynamics.