Study of vertical line source dispersion in a turbulent channel flow

Abstract

Turbulent dispersion of passive concentration released from a vertical line source in a fully-developed channel flow is studied using direct numerical simulation (DNS). The investigation into the turbulent transport processes of the momentum and concentration is conducted in both physical and spectral spaces, based on a systematic analysis of the statistical moments of the velocity and concentration fields, probability density functions (PDFs) of the concentration fluctuations, and the characteristic wavelengths of energetic eddies that dominate turbulent mixing processes. It is observed that the plume development experiences turbulent convective- and diffusive-stages through a comparative study of the spatial and temporal scales of the velocity and concentration fields. It is also observed that the meandering ratio is small near the ground and within the turbulent diffusive stage, and PDFs of concentration fluctuations are sensitive to both the wall-normal distance and the downstream distance from the concentrated line source.