(479i) Forces on Non-Spherical Particle in the Vicinity of Rough Wall at Finite Reynolds Number

Particulate flows of non-spherical particles are encountered in several engineering operations such as flow of suspensions in closed conduits etc. Presence of wall and its structure, greatly affect the hydrodynamic forces acting on moving particles. Here we have numerically studied drag and lift forces acting on a stationary ellipsoid particle situated near the rough wall.

Three dimensional fully resolved simulations based on Finite Element Method are used for the present study. The investigations are performed in the range of shear Reynolds number 10 to 100. The location of the particle and its orientation angle are two important variables in the present study. The clearance between particle surface and rough bed is systematically varied, from one tenth of the particle diameter to several particle diameters. Similarly orientation angle of particle with respect to flow is varied from θ = 0^O (streamlined particle) to θ = 90^O (facing normal to flow). Initially an undisturbed uniform shear flow is allowed to develop then the particle is placed above the wall at specified orientation and location.

Our study reveals a significant variation in drag, and lift coefficient depending on its location from wall and orientation angle. A major variation in drag coefficient is seen as the particle moves away from wall for orientation angle less than 90 degree. Different regimes of lift force are observed depending upon orientation angle. At θ = 0^O (streamlined particle), lift coefficient decreases with particle distance from wall, and direction of lift is away from the wall. For, 90^O > θ > 0^O, lift changes the sign and the force direction is towards the wall. Finally when θ = 90^O (facing normal to flow), lift coefficients become very low, even though fluctuation in the data is observed.