Characterization of Particle Entrapment and Clustering in Wall-Bounded Turbulence

We study the dynamics of inertial particles in turbulent channel flow, focusing on the mechanisms that govern their preferential concentration and entrapment within coherent vortical structures. Both light (bubble-like) and heavy particles are considered, spanning a range of Stokes numbers relevant to turbulent boundary layers. The fluid velocity field is computed using direct numerical simulations (DNS) with the spectral PDE solver Dedalus, for low to moderate Reynolds numbers. Lagrangian particle trajectories are integrated independently using a point-particle approximation and explicit time stepping. To investigate the relationship between particle clustering and turbulence structure, we analyze particle distributions in relation to the swirl criterion, Lagrangian Coherent Structures (LCS), and characteristic fluid time scales derived from vorticity and strain. Our results show distinct behaviors between heavy particles and bubbles, with bubbles tending to accumulate within vortical cores and heavy particles being expelled toward high-strain regions. These trends are quantified using statistical measures of particle concentration conditioned on coherent structures and time-resolved vortex persistence. The analysis highlights how particle inertia and density control the degree and location of clustering, providing insight into the physical mechanisms driving particle–vortex interactions in wall-bounded turbulence.