Settling of finite-size particles in an ambient fluid: A Numerical Study

We have investigated the gravity induced settling of finite-size particles in an ambient fluid by means of direct numerical simulation (DNS). Such configurations are relevant to a large number of applications such as meteorology, mechanical and environmental engineering. For single particle a variety of motion patterns exist, from straight vertical to fully chaotic paths, for which the fluid motion in the near field around the particles and the particle wake play a dominant role. Here, the interface between the dispersed- and carrier-phase was fully resolved by means of an immersed boundary method. Particular care has been taken to meet the respective resolution requirements. We have performed simulations of particles settling with two different Galileo numbers, ���� = 121 and ���� = 178. The settling regimes for a single particle settling with this Galileo numbers are: (a) steady axisymmetric regime and (b) steady oblique regime. We observed, that in the steady oblique regime (���� = 178) the particles exhibit wake induced clustering, while in the steady axisymmetric regime (���� = 121) this was not observed. Furthermore, the mean settling velocity of the particles with ���� = 178 was strongly enhanced compared to the velocity of a single settling particle.