Near-wall accumulation of inertial particles in compressible turbulent channel flows

In the present study, the accumulation of inertial particles in compressible turbulent channel flow is investigated by direct numerical simulations. In particular, an investigation is conducted into how the Mach number and Stokes number affect particle transport, where Mach numbers are taken as Ma=1.5 and 3, Stokes numbers (St0+) span from 1 to 200, and the Reynolds number is fixed at Re=3000. It is found that particles tend to concentrate in the low-velocity, high-density, and low-temperature streaks within the near-wall region. Meanwhile, an increase in the Mach number weakens the preferential concentration of particles in this near-wall region, which is associated with the enhanced near-wall coherent structures. Furthermore, the effects of flow compressibility and rarefaction on particle transport promote the concentration of particles with low inertia (St0+=1,5) and high inertia (St0+=100,200). To further understand this phenomenon, the local Stokes number (Stl+) is employed to quantify the particle inertia relative to the local flow in compressible flows.