Self-similar transport of inertial particles in a turbulent boundary layer

Results are presented from a direct numerical simulation of a particle-laden spatially developing turbulent boundary layer up to Re θ = 2500. The peculiar feature of a boundary-layer flow seeded with heavy particles is the variation of the local dimensionless parameters defining the fluid-particle interactions along the streamwise direction. Two different Stokes numbers can be defined, one using inner flow units and the other with outer units. Since these two Stokes numbers exhibit different decay rates in the streamwise direction, we find a decoupled particle dynamics between the inner and the outer region of the boundary layer. Preferential near-wall particle accumulation is similar to that observed in turbulent channel flow, while different behaviour characterizes the outer region. Here the concentration and the streamwise velocity profiles are found to be self-similar and to depend only on the local value of the outer Stokes number and the rescaled wall-normal distance. These new results are powerful in view of engineering and environmental applications and corresponding flow modelling. © 2012 Cambridge University Press.