DNS of vertical plane channel flow with finite-size particles: Voronoi analysis, acceleration statistics and particle-conditioned averaging

TL;DR

This study uses direct numerical simulation to analyze dilute turbulent particulate flow in a vertical channel, revealing persistent large-scale structures, slightly ordered particle distributions, and detailed wake decay behaviors.

Contribution

It extends previous simulations by doubling the domain length, confirming the persistence of large-scale structures and providing new insights into particle distribution and wake decay in turbulent flows.

Findings

Large-scale structures persist in extended domain.

Particle distribution is slightly more ordered than random.

Wake velocity deficits decay as 1/x and 1/x^2 in near and far wakes.

Abstract

We have performed a direct numerical simulation of dilute turbulent particulate flow in a vertical plane channel, fully resolving the phase interfaces. The flow conditions are the same as those in the main case of "Uhlmann, M., Phys. Fluids, vol. 20, 2008, 053305", with the exception of the computational domain length which has been doubled in the present study. The statistics of flow and particle motion are not significantly altered by the elongation of the domain. The large-scale columnar-like structures which had previously been identified do persist and they are still only marginally decorrelated in the prolonged domain. Voronoi analysis of the spatial particle distribution shows that the state of the dispersed phase can be characterized as slightly more ordered than random tending towards a homogeneous spatial distribution. It is also found that the p.d.f.'s of Lagrangian particle accelerations for wall-normal and spanwise directions follow a lognormal distribution as observed in previous experiments of homogeneous flows. The streamwise component deviates from this law presenting significant skewness. Finally, a statistical analysis of the flow in the near field around the particles reveals that particle wakes present two regions, a near wake where the velocity deficit decays as 1/x and a far wake with a decay of approximately 1/(x*x).