Singularity of inertial particles concentration in the viscous sublayer of wall-bounded turbulent flows

Exact kinetic equation for PDF of inertial particle transported by the fluid with non-Gaussian velocity field in the viscous sublayer are analyzed by asymptotic methods. Power-law type singularity in the vicinity of the wall is shown for the concentration manifesting the phenomenon of particle accumulation. Power exponent dependence from the particle relaxation time derived analytically is in good agreement with the data of DNS/Lagrangian tracking simulations. Singularity is also found for the flatness, skewness and standardized higher-order moments of particle velocity resulting from the presence of two groups of particles free-flight and diffusional with drastically different values of fluctuating velocities.