van M Marleen Aartrijk

Single-particle, particle-pair, and multiparticle dispersion of fluid particles in forced stably stratified turbulence

The dispersion of fluid particles in statistically stationary stably stratified turbulence is studied by means of direct numerical simulations. Due to anisotropy of the flow, horizontal and vertical dispersion show different behavior. Single-particle dispersion in horizontal direction is similar to that in isotropic turbulence for short times, but shows a long-time growth rate proportional to t2.1±0.1, larger than the classical linear diffusion limit. In vertical direction, three successive regimes can be identified: a classical t2-regime, a plateau that scales as N−2, and a diffusion limit where dispersion is proportional to t. By forcing the flow and performing long-time simulations, we are able to observe this last regime, which was predicted but not observed before in stratified turbulence. This diffusive regime is caused by molecular diffusion of the active scalar (density). The mean squared separation of particle pairs (relative dispersion) in vertical direction shows two plateaus that are not prese...

Vertical dispersion of light inertial particles in stably stratified turbulence: The influence of the Basset force

The dispersion of light inertial particles

Dispersion of (Light) Inertial Particles in Stratified Turbulence

\rho_p/\rho_f = \mathcal{O}(1)

Dispersion of heavy particles in stably stratified turbulence

in statistically stationary stably stratified turbulence is studied by means of direct numerical simulations. The light particle dispersion behavior is found to be comparable to that of heavy particles when displayed as a function of the Stokes number. Deviations from fluid particle dispersion are found already for small Stokes numbers; the length of the typical plateau for vertical dispersion is shorter for the light inertial particles. All the forces in the Maxey-Riley equation are taken into account and they are found to be of similar magnitude as the Stokes drag for particles with

Aggregate formation in 3D turbulent-like flows

\rho_p/\rho_f = \mathcal{O}(1)

Forces on light particles in stratified turbulence

. However, not all forces directly influence the particle dispersion. It is shown that especially the often neglected Basset force plays a considerable role in the vertical dispersion of light particles in stratified turbulence. Neglecting this force results in an overprediction of the vertical dispersion by about 15%-20%.

The effect of stable stratification on fluid particle dispersion

We present a brief overview of a numerical study of the dispersion of particles in stably stratified turbulence. Three types of particles arc examined: fluid particles, light inertial particles (

Preferential concentration of heavy particles in stably stratified turbulence

\rho_p/\rho_f = \mathcal{O}(1)

The dynamics of small inertial particles in weakly stratified turbulence

) and heavy inertial particles (

Light particle dispersion in stably stratified turbulence

\rho_p/\rho_f \gg 1