High-performance simulations of colliding inertia-particles in isotropic turbulence

This study develops an efficient parallel simulation of colliding particles in stationary isotropic turbulence. Flow is computed with a fourth-order finite-difference method and particles are tracked with the Lagrangian method. Particle collisions are efficiently detected by the cell-index method, which is often used in molecular dynamics simulations. The developed code is written in Fortran 90 in conjunction with MPI library. Auto-parallelization directives are inserted in the code for shared-memory parallelization, making it possible to run the code in the so-called hybrid-parallelization mode. The code is designed to minimize the MPI communication, which results in a high parallel performance. The present simulation has been run on up to 512 ³ grids with 10 million particles. The largest simulation has successfully obtained the collision frequencies for the Taylor-scale-based Reynolds number, Re _γ, of 209, which is much larger than previously attained maximum Rs _γ of 85 in particle collision simulations. The collision frequencies obtained in this study have shown that a collision frequency model underestimates the frequency in high Re _γ flows.