Spatial evolution of inertial particles in a turbulent pipe flow

The dynamics of small inertial particles transported by a turbulent flow is crucial in many engineering applications. For instance internal combustion engines or rockets involve the interaction between small droplets, chemical kinetics and turbulence. Small, diluted particles, much heavier than the carrier fluid, are essentially forced only by the viscous drag i.e. the Stokes drag (gravity, feedback on fluid and collisions are neglected). The difference between particle velocity V and fluid U produces various anomalous phenomena such as small-scale clustering or preferential accumulation at the wall even for incompressible flows. To stress the interaction between wall bounded flows and particle dynamics we have performed a direct numerical simulation of a fully-developed particle-laden pipe flow. Seven different populations of particles are injected at a fixed location on the axis of the pipe and their evolution is analyzed for a streamwise extension of 200R ( with R the pipe radius) to asses the onset of turbophoresis.