Eulerian-Lagrangian DNS/LES of particle-turbulence interactions in wall-bounded flows

We developed a code for the direct numerical simulation of particle-laden turbulent flows, using the Eulerian-Lagrangian point-particle approach. The code uses a semi-implicit coupling scheme between the particles and the fluid, and a standard finite-volume single-phase solver, which can run either in DNS or LES mode; it can consider either one- or two-way coupling between the particles and the fluid. The code was used to study the dynamics of the particle-turbulence interactions in channel and pipe flows loaded with small, heavy particles. We present some results, from both an instantaneous-structure perspective (fluid turbulence structures and particle-concentration patterns), and a statistical perspective (probability distribution functions and correlations). Our results suggest that the near-wall particle-fluid interaction can be understood in terms of the interaction of the particles with the streamwise vortices. The strong streamwise vortices above the wall are responsible for the elongated streaky patterns that occur both in the deposition and resuspension of the particles. When two-way coupling is considered, the particles produce a large damping in the intensity of the streamwise vortices, without any significant change in their shape and their size. This damping leads to a weakening of the near-wall streaky-pattern, and to a reduction in the accumulation of particles at the wall.