Effects of Urban-Like Topography on Particle Transport In Turbulent Flow

In this research, we examine the turbulent transport of particles in urban-like environments. Direct numerical simulation is used to investigate how the secondary flows from building arrays affect particle concentration and recirculation. The buildings are represented using immersed boundary methods, and the particles are represented using a one-way coupled Eulerian Lagrangian point particles model. To capture the complex interaction between the particles and the building surface geometry, a signed distance function is used to determine whether a particle is at or near a building’s surface. A particle at the surface will experience a fully elastic collision. We analyzed the particle statistics in a half-channel flow with a friction Reynolds number Re_τ = 200 at three different particle Stokes numbers, St = 5, 25, and 100 over five building arrays and a smooth wall case. The five building configurations are created by systematically varying the spanwise spacing of cubic arrays from δ/4 to 4δ, where δ is the half-channel height. In all rough wall cases, the size of the roughness geometry is equal to δ/8, and the streamwise spacing is δ/4. We observed that the roughness spacing had a greater effect on particles with a lower Stokes number, and particle clustering above the roughness increased with roughness density.