Finite-size particles in turbulent channel flow: quadrant analysis and acceleration statistics

ABSTRACT

The interaction between finite-size particles and turbulent channel flow in the absence of gravity is studied by direct numerical simulations (DNS). The study is motivated by DNS observations of a turbulent channel flow with high-density, pointwise particles, that cluster in regions of high streamwise root-mean-square (RMS) acceleration close to the wall, contrary to what is observed in homogeneous isotropic turbulence. The aim of the present study is to explore if this is still the case when size effects are taken into account in the DNS. Based on the analysis of the velocity and acceleration statistics, the present DNS shows that, close to the wall, particles with ρ_p/ρ_f ranging from 2 to 4 are surrounded by regions with low streamwise RMS velocity but high streamwise RMS acceleration. According to the normalised particle acceleration probability density functions (PDFs), size effects become important in the near-wall region. As particle inertia increases, the normalised PDFs of particle acceleration tend to a Gaussian distribution. The tails of the normalised PDFs of the fluid conditioned by the presence of particles are higher than that of the unconditioned fluid close to the wall.

KEYWORDS:

• DNS
• finite-size particles
• quadrant analysis
• acceleration statistics

Acknowledgments

Simulations have been performed on the P2CHPD cluster. The authors wish to thank C. Pera for technical support.

Disclosure statement

No potential conflict of interest was reported by the authors.