Clustering of heavy particles in the inertial subrange of isotropic turbulence

The dynamics of inertial heavy particles in high Reynolds number turbulence, notably particle clustering, are important fundamental processes, e.g., for raindrop formation in atmospheric flows. Three-dimensional direct numerical simulations of particle-laden homogeneous isotropic turbulence are performed at resolution 4096^3 for Re_\lambda = 648 and with 3.2 x 10^9 particles for several Stokes numbers. The results show clustering of inertial particles in the inertial subrange at high Reynolds number, in addition to the clustering typically observed in the near dissipation range. The particle number density spectra manifest a bump in the inertial subrange which is shown to be due to modulation of preferential concentration. It is also found that the number density spectra in the inertial subrange are a function of the scale-dependent Stokes number. For details we refer to Matsuda et al., Phys. Rev. Lett., 132, 234001, 2024.