The three-dimensional flow contained in a rapidly rotating circular split cylinder is studied numerically solving the Navier--Stokes equations. The cylinder is completely filled with fluid and is split at the midplane. Three different types of boundary conditions were imposed, leading to a variety of instabilities and complex flow dynamics. The first configuration has a strong background rotation and a small differential rotation between the two halves. The axisymmetric flow was first studied identifying boundary layer instabilities which produce inertial waves under some conditions. Limit cycle states and quasiperiodic states were found, including some period doubling bifurcations. Then, a three-dimensional study was conducted identifying low and high zimuthal wavenumber rotating waves due to Görtler and Tollmien-Schlichting type instabilities. Over most of the parameter space considered, quasiperiodic states were found where both types of instabilities were present. In the second configuration, both cylinder halves are in exact counter-rotation, producing an O(2) symmetry in the system. The basic state flow dynamic is dominated by the shear layer created in the midplane. By changing the speed rotation and the aspect ratio of the cylinder, the flow loses symmetries in a variety of ways creating static waves, rotating waves, direction reversing waves and slow-fast pulsing waves. The bifurcations, including infinite-period bifurcations, were characterized and the flow dynamics was elucidated. Additionally, preliminary experimental results for this case are presented. In the third set up, with oscillatory boundary conditions, inertial wave beams were forced imposing a range of frequencies. These beams emanate from the corner of the cylinder and from the split at the midplane, leading to destructive/constructive interactions which produce peaks in vorticity for some specific frequencies. These frequencies are shown to be associated with the resonant Kelvin modes. Furthermore, a study of the influence of imposing a phase difference between the oscillations of the two halves of the cylinder led to the interesting result that different Kelvin modes can be excited depending on the phase difference.

Abstract: Numerical investigations of flow past rotating circular cylinders with and without wires wrapped on the surface of the cylinder were studied using Computational Fluid Dynamics (CFD). The flow characteristics such as flow separation, shedding of the primary and secondary vortices, and drag coefficients were investigated. The software STAR CCM+ from Siemens PLM was used in all investigations. Three-dimensional Unsteady Reynolds Average Navier Stokes (URANS) equations were utilized. The free stream mean velocity was constant at 10 m/sec, which corresponded to an approximate Reynolds number based on cylinder’s diameter of 32,000. The results are presented for cylinders with and without wires at varying rotation rates [alpha] of 0, 0.5, and 1. This is represented by [alpha], the ratio of the tangential velocity at the cylinder to that of the free stream velocity of the flow. As the rotation rate increased from 0 to 1, the drag coefficient for the smooth rotating cylinder reduced, while the drag coefficient for the wire-wrapped cylinder increased. The wire-wrapped cylinder produced significantly higher lift when compared with the corresponding value for the smooth cylinder. Increasing the rotation rate increases the lift and lift to drag ratio.

This text offers an authoritative compilation of experimental data, theoretical models, and computer simulations which will provide the reader with a comprehensive survey of research work on the phenomenon of flow around circular cylinders.

Powder flow has attracted increased attention in recent years as novel formulated and functional products are being developed in powder forms, particularly in pharmaceutical and high value additive manufacturing industries. This book meets a need for a truly integrated modern treatment of dry powder flow, covering theory, robust characterisation techniques, modelling tools and applications. Written by leaders in the field, the book opens by introducing the wide range of powder processing problems faced by industry, the complexities of powders and the myriad of ways their flow behaviour can be characterised. The authors then move on, with contributions from experts, to describe fundamental properties that can be measured, defining the states of stress and shear rate and the considerations that need to be taken account. By providing a comprehensive treatment of all available characterisation techniques, as well as various modelling tools, the reader obtains a clear, practical overview. Case studies and applications connect theory to practical examples across a broad range of industries. This book stands out by not only providing the reader with guidance on what to measure but also how to interpret results, ensuring this is an invaluable text for anyone working on powder flow in the chemical, pharmaceutical and manufacturing industries, as well as students and researchers across chemical and process engineering disciplines.