关键词: numerical simulations, TVD schemes, NND schemes, implicit NND schemes, turbulent channel flow, finite-size particle, direct numerical simulation (DNS)

Abstract: A direct-forcing fictitious domain (DFFD) method is used to perform fully resolved numerical simulations of turbulent channel flows laden with large neutrally buoyant particles. The effects of the particles on the turbulence (including the mean velocity, the root mean square (RMS) of the velocity fluctuation, the probability density function (PDF) of the velocity, and the vortex structures) at a friction Reynolds number of 395 are investigated. The results show that the drag-reduction effect caused by finite-size spherical particles at low particle volumes is negligibly small. The particle effects on the RMS velocities at Re_τ=395 are significantly smaller than those at Re_τ=180, despite qualitatively the same effects, i.e., the presence of particles decreases the maximum streamwise RMS velocity near the wall via weakening the large-scale streamwise vortices, and increases the transverse and spanwise RMS velocities in the vicinity of the wall by inducing smaller-scale vortices. The effects of the particles on the PDFs of the fluid fluctuating velocities normalized with the RMS velocities are small, regardless of the particle size, the particle volume fraction, and the Reynolds number.

Key words: numerical simulations, TVD schemes, implicit NND schemes, NND schemes, direct numerical simulation (DNS), turbulent channel flow, finite-size particle