Eulerian-Lagrangian Simulation of Turbulent Flow with Finite-Size Particles

Multiphase flow plays a critical role in numerous industrial processes and engineering applications. This research primarily concerns the numerical modeling of particle tracking in turbulent flows with the aim of understanding the complex interactions between turbulent structures and particle motion. Both the point-particle and fully-resolved techniques are employed, with the focus being the fully-resolved simulation of finite-size particles. For the simulation of point particles, a Lagrangian particle tracking subroutine is developed and integrated with an in-house turbulent channel flow solver. A turbulent channel flow with 500,000 particles is simulated using the solver, and strong preferential concentrations are observed due to the particle interaction with vortical structures. The finite-size particles are simulated within the framework of OpenFOAM using the Immersed Boundary Method (IBM) combined with Direct Numerical Simulation (DNS). Two different IBM techniques are examined, specifically the discrete forcing approach and the cut-cell method. It is concluded that the cut-cell method is a superior technique for studying particulate flows due to the less severe spurious force oscillations (SFOs) on a coarse grid. Simulation of particles in a two-dimensional channel shows that these non-physical oscillations can adversely influence the prediction for the motion of light particles. The cut-cell method is further examined by simulating several benchmark flows and comparing the results with experimental data. A satisfactory agreement between the simulation results and experimental data is observed. Fully-resolved simulations are conducted to investigate the behavior of spherical and ellipsoidal particles, and the results show different behaviors despite identical initial conditions and equivalent volumes and Stokes numbers. This difference is attributed to the shape factor of the particles. Analysis of the Q-criterion reveals the formation of hairpin and vortex ring structures as the particles interact with flow. Furthermore, it is demonstrated that particle motion is significantly influenced by its interaction with vortices near the wall. In addition, the collision and close interaction of two finite-size spherical particles are investigated, revealing significant alterations to the flow pattern and particle motion, especially when one particle is located in the wake of the other. Finally, a comparison between the fully-resolved technique and the point-particle approach is conducted. The findings demonstrate that while the point-particle method is computationally more efficient, it lacks the capability to provide realistic representation of fluid-particle interactions