Large Eddy Simulation Of Turbulent Gas-Particle Flow In A Channel

The interaction between coherent fluid structure and particle near the wall is one of most important topic in wall-bounded gas-particle turbulence, which would have significant impact on particle wall boundary condition development and understanding of turbulence modulation mechanism.This thesis provides a primary investigation on gaseous turbulence and gas-particle turbulent flow in a channel by aid of large eddy simulation (LES), where the gaseous governing equation were solved by second-order central difference scheme, with sub-grid scale modeled by dynamic model, pressure-momentum coupling by fractional-step projection method, and fast solving of Poission equation by FFT method; and the particle momentum equation solved by second-order Runke-Kutta integration, where the fluid velocity at particle position were interpolated from gaseous field using second Lagrangian scheme. Three-dimension simulation of turbulent gas flows (Re(=180) was first performed. The statistical properties of fluid obtained by current study, including average velocity, fluctuated velocity et al., agree well with previous DNS results. Subsequently, the turbulent diffusion behaviors of three kinds of suspended particles (with Stokes number of 0.5, 5 and 36) in the channel were investigated. It shows that, both the streamwize averaged velocities and fluctuated velocities are non-zero near the wall boundary, and its value increased while the particle St increased; the particle fluctuated velocities in cross-streamwise and spanwise are less than those of fluid, and the heavier the particle, the less the fluctuated velocities; the particles velocity fluctuations are highly anisotropic, as those of fluid, and its anisotropy increased with particle inertia;the particle number concentration near the wall are higher than those at the central line for all particles, with the moderate inertia particle has the highest non-uniformity. Finally, the impact of Reynolds number of channel flows on particle motion were discussed by comparing results of flow with Reynolds number of 180 and 395. And it shows the particle fluctuated velocities increase with increased Re, while the particle prefer concentration show similar behaviors of previous different particles, which reveals the dominant impact of particle Stokes number.