S. Musacchio

Dynamics and statistics of heavy particles in turbulent flows

We present the results of direct numerical simulations (DNS) of turbulent flows seeded with millions of passive inertial particles. The maximum Reynolds number is Re λ∼ 200. We consider particles much heavier than the carrier flow in the limit when the Stokes drag force dominates their dynamical evolution. We discuss both the transient and the stationary regimes. In the transient regime, we study the growth of inhomogeneities in the particle spatial distribution driven by the preferential concentration out of intense vortex filaments. In the stationary regime, we study the acceleration fluctuations as a function of the Stokes number in the range St ∈ [0.16:3.3]. We also compare our results with those of pure fluid tracers (St = 0) and we find a critical behavior of inertia for small Stokes values. Starting from the pure monodisperse statistics we also characterize polydisperse suspensions with a given mean Stokes, .

Acceleration statistics of heavy particles in turbulence

We present the results of direct numerical simulations of heavy particle transport in homogeneous, isotropic, fully developed turbulence, up to resolution

Inverse energy cascade in three-dimensional isotropic turbulence

512^3

Clustering and collisions of heavy particles in random smooth flows

(

Evidence for the double cascade scenario in two-dimensional turbulence.

R_\lambda\approx 185

Lyapunov exponents of heavy particles in turbulence

). Following the trajectories of up to 120 million particles with Stokes numbers, St , in the range from 0.16 to 3.5 we are able to characterize in full detail the statistics of particle acceleration. We show that: (i) the root-mean-squared acceleration

Two-dimensional elastic turbulence

a_{\rm rms}

Kolmogorov scaling and intermittency in Rayleigh-Taylor turbulence

sharply falls off from the fluid tracer value at quite small Stokes numbers; (ii) at a given St the normalized acceleration

Relaxation of finite perturbations: Beyond the fluctuation-response relation

a_{\rm rms}/(\epsilon^3/\nu)^{1/4}

Statistics of mixing in three-dimensional Rayleigh-Taylor turbulence at low Atwood number and Prandtl number one

increases with