Statistical simulation of particle deposition on the wall from turbulent dispersed pipe flow

Abstract

Deposition of particles towards the wall from a turbulent dispersed flow in a vertical pipe has been studied numerically. A fully developed turbulent pipe flow of air is chosen as the primary flow, and it is represented by the law-of-the-wall relations and the average turbulence statistics obtained from a direct numerical simulation reported in the literature. Trajectories and velocities of the particles are calculated, using a one-way coupling Lagrangian eddy–particle interaction model. Thousands of individual particles (typically 920 kg/m3 in density) of various diameters (2.0–68.5 μm) are released in the represented flow, and deposition velocities are evaluated. It is shown that the deposition velocities predicted are in good agreement with experimental data available in the literature. The influence of some forces in the particle equation of motion (i.e., the Saffman lift force, the centrifugal force, the conservation of angular momentum and the buoyancy force) on the prediction of the deposition velocities is examined. Also examined is the influence of the inlet particle concentration profile, on which little attention has been paid so far. The unique phenomenon of ‘near-wall build-up’ of small particles, which has been reported in some previous simulations and experiments, was also observed in the present simulation while the result for very small particles (τp+<3) should be accepted with reservation due to their possible spurious build-up associated with the random-walk approach.