Numerical simulation of two-way coupling effects in a particle-laden turbulent pipe flow

The effect of dispersed, dense solid particles on turbulence in a fully-developed pipe flow at Re_τ = 360 is studied using large eddy simulation with no explicit subgrid scale model. The continuous and the dispersed phases have been treated using the Eulerian and the Lagrangian approaches respectively. A second-order accurate, finite-volume based, Adams-Bashforth fractional-step scheme is used to integrate the unsteady, three-dimensional Navier-Stokes equations. The particle equation of motion included only the drag force and has been integrated using a fourth-order accurate Runge-Kutta method. The effects of particles on fluid turbulence are investigated by tracking 100000 particles of diameter d_P⁺ = 1.20 (in wall units) at a volumetric ratio of φ_v 5 × 10^-4. It is observed that two-way coupling reduces the preferential concentration of particles near the wall. Also, both the streamwise mean and the RMS velocities of the continuous phase are augmented due to the two-way coupling. However, the process of augmentation of the fluid streamwise RMS velocities is not monotonous with time. A small initial attenuation followed by a significant augmentation is observed. On the other hand, the fluid radial RMS fluctuations are damped due to the effect of particles on the fluid. This damping of radial fluctuations is responsible for lowering the concentration of particles near the wall.