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Vortex shedding over a circular cylinder is modeled based on the weakly compressible flow equations with a simple subgrid scale turbulence model and a simple hybrid boundary condition. An explicit finite volume method is used. A subcritical and a supercritical case are computed. It is shown that the large-scale vortex-shedding phenomenon, the primary vortices, and the related oscillatory lift and drag can be calculated fairly well with a grid system coarser than the boundary layer thickness. The secondary vortices and the related higher frequency oscillations are also calculated by using somewhat finer grids.
This is a concise and comprehensive review of the progress made during the past two decades on vortex induced vibration (VIV) of mostly circular cylindrical structures subjected to steady uniform flow. The critical elements of the evolution of the ideas, theoretical insights, experimental methods, and numerical models are traced systematically; the strengths and weaknesses of the current state of the understanding of the complex fluid/structure interaction are discussed in some detail. Finally, some suggestions are made for further research on VIV. The organization of the paper is given at the end of the next section.
This book discusses the subject of wave/current flow around a cylinder, the forces induced on the cylinder by the flow, and the vibration pattern of slender structures in a marine environment.The primary aim of the book is to describe the flow pattern and the resulting load which develops when waves or current meet a cylinder. Attention is paid to the special case of a circular cylinder. The development in the forces is related to the various flow patterns and is discussed in detail. Regular as well as irregular waves are considered, and special cases like wall proximities (pipelines) are also investigated.The book is intended for MSc students with some experience in basic fluid mechanics and for PhD students.
This report presents the results on an extensive experimental investigation of the in-line and transverse forces acting on smooth and rough circular cylinders placed in oscillatory water flow at Reynolds numbers up to 700,000, Keulegan-Carpenter numbers up to 150, and relative roughnesses from 0.002 to 0.02. The drag and inertia coefficients have been determined through the use of the Fourier analysis and the least-squares method. The transverse force (lift) has been analyzed in terms of its maximum, semi-peak-to-peak, and root-mean-square values. In addition, the frequency of vortex shedding and the Strouhal number have been determined.
Abstract: The main objective of this thesis is to study the flow characteristics of a rotary cylinder with a symmetric end plate. We performed the simulations for different velocity ratios (0, 5, 10, and 15), aspect ratios (9.053 and 18) at high Reynolds numbers (1.15 x 10 4 {600} Re {601} 6.44 x 105). We then studied the wake structure, the vortices formed in the wake region, the effect of vortex formation on the aerodynamic forces such as lift and drag. We performed computational fluid dynamics (CFD) simulations using a CFD solver, STAR-CCM+ from CD-Adapco. The results show that when the circular cylinder is stationary, the vortex shedding frequency is high; the upper and lower vortices show an asymmetrical process with the wake centerline. A significant vortex pairing can also be seen. But, with the rotation and increase in velocity ratio, the strength of vortex shedding decreases and after velocity ratio 5 the periodic vortex shedding is suppressed. The structure of the wake also modifies depending on the direction of the rotation. When aspect ratio of the circular cylinder is increased, the lift force generated on the cylinder surface is decreased. When an end plate is introduced in the region close to the stationary circular cylinder, it creates interference in the vortex formation and hence, the instabilities in the fluid flow due to vortices are decreased. The geometry of the stationary circular cylinder with an end plate seems to behave similar to a symmetric airfoil at zero angle of attack. Hence, aerodynamic forces generated on the geometry are constant. When the circular cylinder with the end plate is given a constant rotation, then the vortex formation is suppressed, the wake moves further downstream due to the end plate, the lift force generated on the surface increases and a significant decrease in drag force is also observed.
Fluid Vortices is a comprehensive, up-to-date, research-level overview covering all salient flows in which fluid vortices play a significant role. The various chapters have been written by specialists from North America, Europe and Asia, making for unsurpassed depth and breadth of coverage. Topics addressed include fundamental vortex flows (mixing layer vortices, vortex rings, wake vortices, vortex stability, etc.), industrial and environmental vortex flows (aero-propulsion system vortices, vortex-structure interaction, atmospheric vortices, computational methods with vortices, etc.), and multiphase vortex flows (free-surface effects, vortex cavitation, and bubble and particle interactions with vortices). The book can also be recommended as an advanced graduate-level supplementary textbook. The first nine chapters of the book are suitable for a one-term course; chapters 10--19 form the basis for a second one-term course.
This report presents the results on an extensive experimental investigation of the in-line and transverse forces acting on smooth and rough circular cylinders placed in oscillatory water flow at Reynolds numbers up to 700,000, Keulegan-Carpenter numbers up to 150, and relative roughnesses from 0.002 to 0.02. The drag and inertia coefficients have been determined through the use of the Fourier analysis and the least-squares method. The transverse force (lift) has been analyzed in terms of its maximum, semi-peak-to-peak, and root-mean-square values. In addition, the frequency of vortex shedding and the Strouhal number have been determined.