SIMULATION OF DRAG FORCE ON FRACTAL FLOCS DURING SETTLING THROUGH LATTICE BOLTZMANN METHOD

摘要

The hydrodynamic drag force of fractal flocs during settling is examined by the Lattice Boltzmann method. The relationships between drag forces of fractal flocs and the fractal type, floc size and floc settling velocity are discussed according to the simulations. The analysis of the drag force on fractal flocs shows that the simulations are consistent with calculations from the analytical results. The ratio of drag force on fractal flocs and floc size is linear relationship with the floc settling velocity, which is shown that the flow filed around the flocs is Stokes flow. Moreover, the settling velocities and drag forces on flocs formed by DLCCA are larger than flocs formed by DLA, when the flocs are composed of the same primaries particles.