Professor R. H. Rangel
Arezoo Ardekani, PhD Student
Sadegh Dabiri, Collaborating PhD Student
The dynamics of particle–particle collisions and the bouncing motion of a particle
colliding with a wall in a viscous fluid is numerically investigated. The dependence
of the effective coefficient of restitution on the Stokes number and surface roughness
is analysed. A distributed Lagrange multiplier-based computational method in a
solid–fluid system is developed and an efficient method for predicting the collision
between particles is presented. A comparison between this method and previous
collision strategies shows that the present approach has some significant advantages
over them. Comparison of the present methodology with experimental studies for the
bouncing motion of a spherical particle onto a wall shows very good agreement and
validates the collision model. The effect of the coefficient of restitution for a
dry collision on the vortex dynamics associated with this problem is discussed.
The dynamics of particle–particle collisions in a viscous fluid are numerically investigated. A distributed-Lagrange-multiplier-based computational method in a solid-fluid system is
developed and a collision strategy for general shape objects is presented. In earlier methods, a repulsive force is applied to the particles when their separation is less than a critical value and, depending on the magnitude of this repulsive force, collision may not be prevented or particles may bounce unrealistically. In the present method, upon collision of two or more particles, a uniformly distributed force is added to each particle. The contact force is calculated and the relative velocity of the particles along their line of center vanishes. For nonspherical (or non-cylindrical in 2-D) particles the force due to collision may lead to a torque around the center of mass of each particle. In this situation, the uniform distributed force is modified in order to create a net torque around the center of mass of each particle without changing the net force applied to that particle. The contact force is impulsive at the onset of the collision process and decreases smoothly to zero when contact ends. Particles separate from each other when the contact force vanishes and subsequently, a rigidity constraint is satisfied for each particle separately. Results for systems of multi-particle and general shape objects in a viscous fluid are presented.
Publications
Ardekani, A. M., Dabiri, S., Rangel, R. (2007). Modified DLM method for finite-volume simulation of particle flow. 45th AIAA Aerospace Sciences Meeting, Reno, Nevada. Paper No. AIAA 2007.
Ardekani, A. M., Rangel, R. (2008). Numerical investigation of particle-particle and particle-wall collisions in a viscous fluid. J. Fluid Mech., 596, 436-466.
Ardekani, A. M., Dabiri, S., Rangel, R. (2009). Collision of multi-particle and general shape objects in a viscous fluid. J. Computational Physics, 227, 10094-10107.
Ardekani, A. M., Dabiri, S., Rangel, R. (2009). Deformation of a droplet in a particulate shear flow. Southern California Symposium on Flow Physics.