Motion Of Ellipsoidal Particles Research Articles

Three-dimensional rotational dynamics of prolate particles in a circular tube

The 3D rotational dynamics of prolate particles in a low Re circular tube flow is experimentally analyzed by employing digital holographic microscopy. The 3D rotational motion of prolate particles is observed and compared with the existing theory on 3D particle dynamics. A particle tumbles with different orientations in a low Re tube flow. The rotational period of particles in a circular tube depends on their radial location. The rotational period of particles located at the non-equilibrium position inside the circular tube differs from that in the previous studies. The deviation from the theoretical results increases as the particle locates away from the equilibrium radial position of 0.5R. This experimental analysis provides unrevealed 3D rotational features of prolate particles and can help develop a new model for the rotational motion of ellipsoidal particles in a circular conduit.

A sublayer model for wall deposition of ellipsoidal particles in turbulent streams

A sublayer model for deposition of ellipsoidal particles from turbulent streams on a smooth wall is developed. The analysis is based on the motion of ellipsoidal particles in the coherent vortices of near-wall turbulence. The vortical velocity field is simulated by using a sequence of viscous stagnation point flows with a superposed streamwise turbulence mean flow. The equations of particle motion include the hydrodynamic forces and torques, the shear-induced lift and the gravitational force. Euler's four parameters (quaternions) are used for describing the time evolution of particle orientations. Trajectories of ellipsoidal particles in the modeled flow field are evaluated and the differences with those of thier spherical counterparts are discussed. Based on the observed trajectories and an averaging procedure, the inertia-interception deposition velocities under various conditions are evaluated. The effects of particle size, aspect ratio, particle-to-fluid density ratio, and gravity on deposition velocity are studied. The model predictions are also compared with several available experimental results, and favorable agreements are observed.

S. G. Mason—A retrospective

Without exaggeration one can say that Professor Stanley G. Mason was one of the founders of the science of microrheology. His early interest in this field was aroused when trying to understand the complex behavior of papermaking suspensions, the obvious relevance of which became evident after joining the Pulp and Paper Research Institute of Canada (Paprican) in 1946. Besides his publications with Professor Otto Maass from his thesis work on critical phenomena, his early work deals almost exclusively with the hydrodynamic and colloidal aspects of pulp suspensions. He realized that in order to understand the complexity of such systems, it was necessary to study the properties of the individual pulp fibers that make up the suspension. In this respect the classical work of Jeffery (1922) on the motion of ellipsoidal particles in linear shear flows was extremely relevant. Mason compared a pulp fiber with a long slender spheroid and applied Jeffery's theory to the motion of single suspended fibers. Over the years a large number of papers by Mason and coworkers were devoted to the extensions of Jeffery's work. From this early work came the realization that the properties of suspensions can be understood from a knowledge of the behavior of the suspended particles, a realization which led to the science of microrheology, a term coined first by Mason himself. Mason's early work on papermaking became classical among scientists working in the field of pulp and paper. It led, among other things, to an understanding of the electrokinetic properties