Counterrotating longitudinal vortices in the centreline plane of a circular cylinder, re 550. Vortexinduced vibrations and wake induced oscillations using. The threedimensional 3d, timedependent, incompressible. Vortex dynamics in the wake of a cylinder springerlink. Cylinder wakes exhibit the phenomenon of vortex shedding lockon where the vortex shedding can lockon to a forcing frequency which is different from the. Realtime identification of vortex shedding in the wake of.
Steenhoven mechanical engineering faculty, energy technology section, eindhoven university of technology. The study is performed using planar high framerate particle image velocimetry. Vortex dynamics of a cylinder wake in proximity to a wall. On the vortex dynamics in the wake of a finite surface.
By appropriate impulsive changes of end conditions, spanwise. Threedimensional vortex structures in a cylinder wake 203 figure 1. Flow visualizations and frequency spectra provide a glimpse of the complex vortex dynamics that are observed in the sphere wake. Andersson2 1 department of marine technology, norwegian university of science and technology, no7491 trondheim, norway 2 department of energy and process engineering, norwegian university of science and technology, no7491 trondheim, norway email. In fluid dynamics, vortex shedding is an oscillating flow that takes place when a fluid such as air or water flows past a bluff as opposed to streamlined body at certain velocities, depending on the size and shape of the body. Pdf simulation of vortex dynamics in a cylinder wake by. Detecting vortex formation and shedding in cylinder wakes using. To expand the application of this method, twodimensional, twocomponent velocity data were collected in the wake. The shedding process in the near wake of a surfacemounted, square crosssection cylinder of heighttowidth aspect ratio 4 at a reynolds number of 12,000 based on freestream velocity and the obstacle width was investigated. Threedimensional vortex structures in a cylinder wake. Vortex dynamics in the cylinder wake vortices fluid. Experimental results carried out in a cylinder far wake by williamson and prasad g were used here both to construct the structure of the dynamical systems and as test to validate our model. Simulation of vortex dynamics in a cylinder wake by. Characteristics of energy dissipation in a turbulent cylinder.
Mahbub alam2 1 department of mechanical engineering, kangwon national university. An instantaneous velocity distribution sampled at an arbi trary instant is presented in figs. Resolving vortexinduced pressure fluctuations on a. The presence of lowfrequency fluctuations in the wake of bluff bodies have been observed in several investigations. Energy contents and vortex dynamics in modec transition. Twodimensional flow past a cylinder close to a free surface at a reynolds number of 180 is numerically investigated. Pdf vortex dynamics in a wiredisturbed cylinder wake. The mechanism of wake induced vibrations wiv of a pair of cylinders in a tandem arrangement is investigated by experiments. Selfconsistent mean flow description of the nonlinear. Keywordscircular cylinder, surface roughness, reynolds number, lift and drag coefficient, velocity profile. Introduction the effect on fluid dynamics when a circular cylinder is placed in flow has been studied, to understand the. Detecting vortex formation and shedding in cylinder wakes.
Simulation of vortex dynamics in a cylinder wake by the immersed boundary technique article pdf available in progress in computational fluid dynamics an international journal 103. Abstract the effects of crossflow oscillation of a cylinder on the formation of vortices in its wake are investigated experimentally by means of flowvisualization studies in a 4. Wake turbulence every effort is made to ensure that the information in this booklet is accurate and uptodate at the time of publishing, but many changes can occur over time, especially in regard to airspace and legislation. Also, decreasing the gap spacing reduces the critical vortex suppression speed. Focusing on the dynamics of the vortex shedding phase in the wake planview the plane spanned by the free.
Vortex dynamics in a wiredisturbed cylinder wake i. The primary effect of the wire is the reduction of the velocity. Vortexinduced vibrations of two cylinders in tandem. Laser techniques to fluid mechanics, lisbon, portugal, july 05 08, 2010 4. The impact of the circular cylinder turbulent wake on shedding frequency and strouhal number of the plate were the main aim of this study. On the effects of viscoelasticity on twodimensional. Title, vortex dynamics in a wiredisturbed cylinder wake. Energy contents and vortex dynamics in modec transition of wired cylinder wake i. Flowinduced vibration fiv is an important phenomenon, by which the flow around bluff bodies creates forces that excite vibration. Flow was visualized using hydrogen bubbles generated by a wire placed behind the cylinder. Rather than attempt here to describe the vortex dynamics in both unseparated and separated wakes for all the different types of 3d and nominally 2d body shapes, an overview will be presented of the vortex dynamics phenomena in the wake of a circular cylinder, over a wide range of reynolds numbers.
Furthermore, parezanovic and cadot20,21 characterized the modi. When the two cylinders are sufficiently far apart ld 4 where d is the diameter of the cylinder and l is the distance between the cylinder centers, only the rear cylinder will be affected by the wake of the front cylinder. Aerodynamics of a cylinder in the wake of a vshaped object. Vortex formation in the wake of an oscillating cylinder.
Vortex dynamics in the wake of wallmounted cylinders. Numerical study of the effect of turbulent wake of cylinder. The diameter ratio of the main cylinder and the wire equals d d50 so no vortex shedding is expected to occur for the wire. Bluff body wake flows have direct engineering significance. Our particular interest is the effect of polymer additives on the linear stability of twodimensional viscous flow past a confined cylinder and our investigation involves both direct numerical simulation and the solution of a generalized. A numerical study of a circular cylinder in the wake of an. The simulations are based on a new class of spectral methods suitable for unstructured and hybrid grids. In this research, direct numerical simulation has been performed to study the turbulent wake behind a wallmounted square cylinder with aspect ratio 4 and reynolds number 12 000 based on the freestream velocity and obstacle side length in a developing boundary layer. Vortex shedding dynamics in the laminar wake of cones michel provansal1 and peter a. This cited by count includes citations to the following articles in scholar. Using numerical simulation as a key tool to easily investigate the dynamics of the wake under streamwise harmonic forcing frequency ratio equal to unity at re, the two dimensional flow is analysed in terms of vortex wakes.
Monkewitz1,2 1 irphe aixmarseille university, 49 rue f. Zhou3 1institute for turbulencenoisevibration interactions and control, shenzhen graduate school, harbin institute of technology, shenzhen 518055, china 2school of engineering, university of newcastle, nsw 2308, australia. Energy contents and vortex dynamics in modec transition of wired. Cylinder wake dynamics in the presence of streamwise. Energy contents and vortex dynamics in modec transition of. Vortex dynamics in the cylinder wake semantic scholar.
The aim of this work is to examine wake dynamics and vortex. Vortex suppression and drag reduction in the wake of. Huang2 1shenzhen graduate school, harbin institute of technology xili shenzhen university town, shenzhen 518055, china 2department of mechanical engineering, the hong kong polytechnic university hung hom, kowloon, hong kong, china abstract. Effect of orientation on the wake of a square cylinder at low. The flow over a pair of counterrotating cylinders is investigated numerically and experimentally. This simplified model of the wake dynamics is first validated on a single cylinder for which we consider the 2d response. Vortex and wake induced vibrations in an array of cylinders. Even though the flow past a circular cylinder at re 3900 re u ref d. For flow that is twodimensional, we can define the displacement thickness in terms of the integral in this expression, 7 yh is the normalized vertical crossstream position, uy is. The present paper represents, as far as we are aware, the first linear stability analysis for inertial flows of a viscoelastic fluid around a bluff body. Direct numerical simulation of turbulent wake behind a. In any case, the effects of intermediate triangular cylinder inclinations on the wake stability and flow dynamics have yet to be investigated. The vorticity dynamics at the wake of the cylinder being different at different cylinder orientations can be beneficial in heat transfer enhancement.
On the relationship between the vortex formation process and. On the wakeinduced vibration of tandem circular cylinders. A 3d vortex dynamics analysis in intermediate square. Since the lockon occurs when the near wake behind a cylinder is perturbed at twice the natural shedding frequency, we interrogate the wake.
Dynamics in the turbulent wake of a curved circular cylinder jos e p. Our emphasis is towards steady uniform flow past uniformgeometry cylinders. M e c h a n i c a l and aerospace engineering, upson hall, cornel1 university, ithaca, new york 14853. The diameter ratio of the main cylinder and the wire equals dd50 so no vortex shedding is expected to occur for the wire. Learn to calculate the drag on a body using the velocity profile of the wake. The wake structure present when the cylinders were rotated at speeds below the critical value can be classi. Vortex induced vibrations of a pivoted cylinder are investigated experimentally at a fixed reynolds number of 3100, a mass ratio of 10. Vortex dynamics in the cylinder wake vortex dynamics in the cylinder wake williamson, c h k 19960101 00. Mechanical and aerospace engineering, upson hall, cornel1 university. Lowfrequency unsteadiness in the vortex formation region. Pdf the dynamics of flow past a circular cylinder is investigated at reynolds number re between 20 and 3900 using the rectangular mesh. Dynamics in the turbulent wake of a curved circular cylinder. Numerical assessment of wake dynamics and vortex shedding. Largeeddy simulations les are used to investigate the modifications of wake dynamics and turbulence characteristics behind a circular cylinder placed near a wall for varying gaptodiameter gd ratios where g signifies the gap between the wall and the cylinder, and d the cylinder diameter.
Velocity correlations in the wake behind a cylinder 659 4. We present simulation results of vortex induced vibrations of an infinitely long flexible cylinder at reynolds number re, corresponding to a young turbulent wake i. The dynamics of vortex lockon, downstream of a circular cylinder in an oscillatory flow with nonzero mean velocity, is investigated by applying. Twodimensional compressible viscous flow around a circular cylinder. The dynamics of vortex streets in channels mathematics. The governing equations are solved using a spectral element method for a reynolds number of red100. When marine risers are designed in a tandem arrangement, two aspects of fiv including vortex induced vibration viv and wake induced vibration wiv are very important, resulting in strong vibrations and fatigue damage. The synthetic jet vortex pair interacts with the spanwise vorticity shear layers behind both sides of the cylinder, resulting in the variations of the wake vortex shedding modes at re950. Andersson skip to main content accessibility help we use cookies to distinguish you from other users and to provide you with a. Experimental setup and environmental conditions reported experiments were performed after sunset or during cloudy days, what resulted in very stable temperatures of environmental air. At low reynolds numbers based on cylinder diameter re47 an unsteady wake develops behind the circular cylinder due to instabilities in the separation bubble that. Dynamics and flow structures in the turbulent wake of. On the relationship between the vortex formation process and cylinder wake vortex patterns by david jeonand morteza gharib graduate aeronautical laboratory, california institute of technology, pasadena, ca 91125, usa received 10 july 2004 and in revised form 12 july 2004 the idea of vortex formation time, originally developed for vortex ring. The cylinder was placed in close proximity to the rotor plane, and the pressure fluctuations induced by the rotor wake on the cylinder surface were measured by microphones and fastresponding pressuresensitive paint.
Cellular vortex shedding in the wake of a tapered plate. The field of fluid mechanics is rapidly advancing, driven by unprecedented volumes of data from experiments, field measurements, and largescale simulations at multiple spatiotemporal scales. Pdf the effect of a thin control wire on the wake properties of the flow around a circular cylinder has been investigated numerically. The maximum decrement occurs at a wire position of y wd0. Measurements in the near wake of a square cylinder are taken at 26 diameters downstream of a square cylinder to provide meaningful 3d information regarding the primarysecondary vortical structure interaction. However, the vorticity introduced by the wire in the vicinity of the upper shear layer of the cylinder still affects the vortex dynamics in the wake of the main cylinder. The flow topology between the gaps of triangular cylinders at various reynolds numbers and centretocentre distances remain elusive. The interaction between the flow field of cylinders at. Jul 17, 2006 the dynamics of vortex lockon, downstream of a circular cylinder in an oscillatory flow with nonzero mean velocity, is investigated by applying a timeresolved particle image velocimetry technique. The celerity of the positive vortex shed from the lower side of the cylinder was smaller than that of the upper side shed vortex due. The current study analyzes the dynamics of vortexbounding lagrangian saddle points. For these conditions, the cylinder traces elliptic trajectories, with the experimental conditions producing three out of four possible combinations of orbiting. The reynolds number is 22,000 based on square cylinder edge dimension.
Vortex suppression and drag reduction in the wake of counterrotating cylinders 3 the cylinders. However, little attention has been paid to the dynamics and. Threedimensional vortex dynamics in bluff body wakes. Dynamics of vortex lockon in a perturbed cylinder wake. A numerical study of a circular cylinder in the wake of an airfoil c. Camarri and giannetti further investigated the inversion of the vortex street in the wake of a confined square cylinder. A typical wiv response is characterized by a buildup of amplitude persisting to high reduced velocities. Numerical methodology a solver based on a fourierchebyshev spectral collocation has been developed for direct numerical simulation of. Phase dynamics of karman vortices in cylinder wakes. Vortex dislocation mechanisms in the near wake of a step. However, these studies are based on single triangular cylinder only. The interaction between rotor wake and a cylinder has been studied experimentally in the current work.
Oblique and parallel modes of vortex shedding in the wake of a circular cylinder at low reynolds numbers chk williamson journal of fluid mechanics 206, 579627, 1989. Aerodynamics of a cylinder in the wake of a vshaped object sangil kim1 and md. In the present work, the flow dynamics of the near wake. They introduced the concept of wake stiffness and concluded that it was the wake stiffness. The dynamics of vortex lockon, downstream of a circular cylinder in an oscillatory flow with nonzero mean velocity, is investigated by applying a timeresolved particle image velocimetry technique at the reynolds number 360. Abstract the dynamics of vortex lockon, downstream of a circular cylinder in an oscillatory flow with nonzero mean velocity, is investigated by applying a timeresolved particle image velocimetry technique at the reynolds number 360. Dec 14, 2011 the shedding process in the near wake of a surfacemounted, square crosssection cylinder of heighttowidth aspect ratio 4 at a reynolds number of 12,000 based on freestream velocity and the obstacle width was investigated. The effect of a thin control wire on the wake properties of the flow around a circular cylinder has been investigated numerically. Available formats pdf please select a format to send. Simulation the flow structure and characteristic behind a circular cylinder and a normal flat plate in tandem arrangement with the same diameter and width at six gap ratios was performed. Characteristics of energy dissipation in a turbulent cylinder wake j.
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