1. Introduction

This C++ code is utilized for calculating the trajectory of particles, through the utilization of shared memory parallel calculation with OpenMP. The main code features three key aspects:

• One-way coupling with steady-state CFD results

• Seamless integration with OpenFOAM

• General drag model that is capable of handling sonic flow

Regarding the first feature, the code solves the Basset–Boussinesq–Oseen (BBO) equation, which serves as the governing equation coupled with steady-state field profiles. These field profiles include velocity, pressure, temperature, gas density, and turbulence properties, which are obtained through computational fluid dynamics (CFD) simulations. The particle motion is computed solely by taking into account the fluid's impact on the particle trajectory, without considering the opposite direction (particle to fluid) interaction or inter-particle interaction, thus implying a one-way coupling approach.

In relation to the second feature, the code can read the OpenFOAM mesh geometry file and field profiles directly, without any adjustments required. However, Fluent results are also available, but they need to be transformed to OpenFOAM format before being implemented in this code. The transfer code is also available in the GitHub repository.

Finally, the last feature refers to the drag model, which was developed by Singh et al., 2021, and is capable of computing the drag coefficient in any Reynolds number and Mach number, including supersonic flow.

Figure. Example of particle trajectory calculation results. Trajectories of particles with sizes of 100, 316, 1000, 3162, and 10000 nm in a sonic flow virtual impactor are represented by black lines, while red lines display the calculation domain. The fluid enters from an upper open inlet and is accelerated by the converging nozzle up to approximately 320 m/s. The trajectories depend on the initial particle position and size, owing to differences in inertia.