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Showing papers on "Vortex-induced vibration published in 2013"


Journal ArticleDOI
TL;DR: In this article, the authors investigate the dynamics of an inverted flag and find the conditions under which self-excited flapping can occur, where the inverted flag can be classified into three regimes based on its non-dimensional bending stiffness scaled by flow velocity and flag length, and two quasi-steady regimes, straight mode and fully deflected mode, are observed.
Abstract: The dynamics of an inverted flag are investigated experimentally in order to find the conditions under which self-excited flapping can occur. In contrast to a typical flag with a fixed leading edge and a free trailing edge, the inverted flag of our study has a free leading edge and a fixed trailing edge. The behaviour of the inverted flag can be classified into three regimes based on its non-dimensional bending stiffness scaled by flow velocity and flag length. Two quasi-steady regimes, straight mode and fully deflected mode, are observed, and a limit-cycle flapping mode with large amplitude appears between the two quasi-steady regimes. Bistable states are found in both straight to flapping mode transition and flapping to deflected mode transition. The effect of mass ratio, relative magnitude of flag inertia and fluid inertia, on the non-dimensional bending stiffness range for flapping is negligible, unlike the instability of the typical flag. Because of the unsteady fluid force, a flapping sheet can produce elastic strain energy several times larger than a sheet of the deformed mode, improving the conversion of fluid kinetic energy to elastic strain energy. According to the analysis of the leading-edge vortex formation process, the time scale of optimal vortex formation correlates with efficient conversion to elastic strain energy during bending.

175 citations


Journal ArticleDOI
TL;DR: In this paper, a flow control method is employed to mitigate vortex-induced vibration (VIV) of a circular cylinder by using a suction flow method, and the results indicate clearly that the steady suction-flow control method exhibits excellent control effectiveness and can distinctly suppress the VIV by dramatically reducing the amplitudes of cylinder vibrations, fluctuating pressure coefficients and lift coefficients of the circular cylinder model.

173 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of flow approaching angle (α) on the response of a square cylinder is investigated, and it is found that α affects not only the vibration amplitude but also the lock-in regime.
Abstract: Vortex-induced vibrations (VIV) of a square cylinder at a Reynolds number of 100 and a low mass ratio of 3 are studied numerically by solving the Navier-Stokes equations using the finite element method. The equation of motion of the square cylinder is solved to simulate the vibration and the Arbitrary Lagrangian Eulerian scheme is employed to model the interaction between the vibrating cylinder and the fluid flow. The numerical model is validated against the published results of flow past a stationary square cylinder and the results of VIV of a circular cylinder at low Reynolds numbers. The effect of flow approaching angle (α) on the response of the square cylinder is investigated. It is found that α affects not only the vibration amplitude but also the lock-in regime. Among the three values of α (α = 0°, 45°, and 22.5°) that are studied, the smallest vibration amplitude and the narrowest lock-in regime occur at α = 0°. It is discovered that the vibration locks in with the natural frequency in two regimes of reduced velocity for α = 22.5°. Single loop vibration trajectories are observed in the lock-in regime at α = 22.5° and 45°, which is distinctively different from VIV of a circular cylinder. As a result, the vibration frequency in the in-line direction is the same as that in the cross-flow direction.

119 citations


Journal ArticleDOI
TL;DR: In this article, the Navier-Stokes equations are solved by finite element method and the equation of motion of the cylinders is solved by the fourth-order Runge-Kutta algorithm.
Abstract: Flow induced vibration of two rigidly coupled identical circular cylinders in tandem and side-by-side arrangements at a low Reynolds number of 150 is studied numerically. The two cylinders vibrate in the cross-flow direction and have the same displacement. The Navier-Stokes equations are solved by the finite element method and the equation of motion of the cylinders is solved by the fourth-order Runge-Kutta algorithm. Simulations are conducted for a constant mass ratio of 2 and the gap ratios (defined as the ratio of the centre-to-centre distance between the two cylinders L to the cylinder diameter D) of 1.5, 2, 4, and 6. The reduced velocities range from 0.5 to 15 with an increment of 0.5 for the tandem arrangement and from 0.5 to 30 with an increment of 0.5 for the side-by-side arrangement. It is found that the gap between the two cylinders has significant effect on the response. For a tandem arrangement, the lock-in regime of the reduced velocity is narrower than that of a single cylinder for L/D = 1.5...

102 citations


Journal ArticleDOI
TL;DR: In this article, the flow induced motions (FIM) of two rigid circular cylinders, on end linear-springs, in tandem are studied using two-dimensional Unsteady Reynolds-Averaged Navier-Stokes (2-D URANS) simulations verified by experimental data.

96 citations


Journal ArticleDOI
TL;DR: In this paper, the vortex-induced vibrations of a hinged-hinged pipe conveying fluid are examined, by considering the internal fluid velocities ranging from the subcritical to the supercritical regions.

95 citations


Journal ArticleDOI
TL;DR: In this paper, the vortex shedding phenomenon under stationary and dynamic conditions and vortex-induced vibration are observed and analyzed and the results indicate that regular vortex shedding occurs only at the trailing edge of the downstream box girder under stationary conditions.

87 citations


Journal ArticleDOI
TL;DR: In this paper, the amplitude of a bluff body undergoing vortex-induced vibration (VIV) supported by linear and various nonlinear structural forces is examined, and the potential of nonlinear springs to aid in a VIV-based energy harvesting device is examined.
Abstract: We experimentally examine the amplitude of a bluff body undergoing vortex-induced vibration (VIV) supported by linear and various nonlinear structural forces. This investigation is made possible by our Cyber-Physical Fluid Dynamics force-feedback technique; using it, we can impose arbitrary nonlinear restoring forces on a circular cylinder in our water channel. For the range of nonlinearities examined, detailed analysis allows one to understand and predict the response of the nonlinear structural system using knowledge of a standard, linear VIV system. We also present a case study examining the potential of nonlinear springs to aid in a VIV-based energy harvesting device. Appropriate choices of the spring's nonlinearity allow the hypothetical energy harvester to operate at high performance over a much larger range of Reynolds number than a standard system.

79 citations


Journal ArticleDOI
TL;DR: In this article, a mathematical model is proposed to investigate the dynamic response of an inclined single-walled carbon nanotube (SWCNT) subjected to a viscous fluid flow, where the tangential interaction of the inside fluid flow with the equivalent continuum structure (ECS) is taken into account via a slip boundary condition.

78 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the validity of the Independence principle for properly describing the flow characteristics and the dynamics of structures subjected to oblique flow in VIV experiments with yaw cylinders.

64 citations


Journal ArticleDOI
TL;DR: In this article, an experimental and numerical investigation of a two-degree-of-freedom VIV of a flexibly mounted circular cylinder with variable in-line-to-cross-flow natural frequency ratio is presented.

Journal ArticleDOI
Ju-Won Seo, Ho-Kyung Kim1, Jin Park1, Kwon-Taek Kim1, Ginam Kim 
TL;DR: In this paper, a vortex-induced vibration (VIV) was observed in the upstream deck of a twin cable-supported bridge, which represents the first case of such an observation in an actual long-span cablesupported bridge.

Journal ArticleDOI
TL;DR: In this article, the effect of Strouhal number on the shape of the leading edge vortex is investigated, showing that the resulting vortex structures are at least planform-dependent.
Abstract: Volumetric three-component velocimetry measurements have been performed on low aspect ratio wings undergoing a small amplitude pure plunging motion. This study focuses on the vortex flows generated by rectangular and elliptical wings set to a fixed geometric angle of attack of α = 20°. An investigation into the effect of Strouhal number illustrates the highly three-dimensional nature of the leading edge vortex as well as its inherent ability to improve lift performance. Computational simulations show good agreement with experimental results, both demonstrating the complex interaction between leading, trailing, and tip vortices generated in each cycle. The leading edge vortex, in particular, may deform significantly throughout the cycle, in some cases developing strong spanwise undulations. These are at least both Strouhal number and planform dependent. One or two arch-type vortical structures may develop, depending on the aspect ratio and Strouhal number. At sufficiently high Strouhal numbers, a tip vortex ring may also develop, propelling itself away from the wing in the spanwise direction due to self-induced velocity.

Journal ArticleDOI
TL;DR: In this paper, an active flow control strategy based on zero net mass injection is designed and implemented to assess its efficacy, where a three actuator system in the form of suction and blowing slots are positioned on the cylinder surface.

Journal ArticleDOI
TL;DR: The two targeted energy transfer mechanisms responsible for passive VIV suppression that are observed in the finite-element computations are fully reproduced using the two-DOF reduced-order model.

Journal ArticleDOI
TL;DR: In this article, the effect of the position angle of the small cylinder on the lock-in regime of the VIV was investigated numerically, while the diameter ratio and the mass ratio were kept constant.
Abstract: Two-degree-of-freedom Vortex-Induced Vibration (VIV) of two rigidly coupled circular cylinders of different diameters at a low Reynolds number of 250 is investigated numerically. While the diameter ratio and the mass ratio are kept constant, the study is focused on the effect of the position angle of the small cylinder on the lock-in regime of the VIV. Simulations are carried out for position angles α of the small cylinder ranging from 0° to 180° with an interval of 22.5° and the reduced velocities ranging from 1 to 15 with an increment of 1. In order to find the effect of the gap between the two cylinders on the vibration, two gap-to-diameter ratios (0 and 0.2) are considered. It is found that compared with a single cylinder case, the lock-in regime of the reduced velocity is widened significantly when the position angle of the small cylinder is α = 0°, 22.5°, 90°, or 112.5°. Pulsed beating phenomenon characterized by regular vibration with occasional high-amplitude disturbances at regular or irregular intervals is observed at G = 0 and α = 90°. At α = 135°, more than one lock-in regimes are observed in the computed range of reduced velocity for both gaps (G = 0 and 0.2). Setting a small gap (gap-to-diameter ratio of 0.2) between the two cylinders mitigates the vibration by narrowing the lock-in regime and reducing the vibration amplitude.

Journal ArticleDOI
TL;DR: In this article, the effects of flow ratio, a, on the response of a circular cylinder were investigated numerically by solving the two-dimensional Reynolds-Averaged Navier-Stokes equations, where the flow ratio is defined as the percentage of the steady flow velocity component in the total fluid velocity.

Journal ArticleDOI
TL;DR: In this paper, the drift flux two-phase flow model coupled with a simplified flow boiling model is used to calculate the heat transfer from primary side fluid to secondary side fluid, and the resistances caused by downcomer, tube bundle, support plates and primary separators are considered.

Journal ArticleDOI
TL;DR: In this paper, experiments were carried out in a recirculating water channel over the range of Reynolds number 6000 in order to have a better understanding of the physics involved in vortex-induced motions of floating bodies such as offshore platforms.

Journal ArticleDOI
TL;DR: In this paper, the effect of a strongly nonlinear internal attachment on the vortex-induced vibration (VIV) of a rigid circular cylinder restrained by a linear spring, and constrained to move perpendicularly to the mean flow was investigated.

Journal ArticleDOI
TL;DR: In this paper, a theoretical model for coupled tube-cable vibration was developed to evaluate the SFT structural dynamic response to water current, and approximate numerical analyses were carried out to determine the coupling effect between cable transverse vibrations and tube vertical vibrations.
Abstract: This paper describes an investigation of vortex-induced vibrations in a submerged floating tunnel (SFT) system. A theoretical model for coupled tube-cable vibration was developed to evaluate the SFT structural dynamic response to water current. The differential equations of the cable and tube coupled motion were derived using the Hamilton principle, and approximate numerical analyses were carried out to determine the coupling effect between cable transverse vibrations and tube vertical vibrations. The results showed that the maximum amplitudes of the cables were greater than the initial disturbance when self-induced resonance occurred. Self-induced resonance can be caused by the vortex-induced vibration of the cables when the flow velocity reaches a certain value. The change in the tube-specific gravity ratio had little effect on the maximum vibration amplitudes of the tube and cables. The vibrations of the tube and cables were more sensitive to changes in the lift coefficient than to the added ma...

Journal ArticleDOI
TL;DR: In this article, a combined numerical and experimental study examining vortex-induced vibration (VIV) of a neutrally buoyant tethered sphere has been undertaken, with the numerical ( ) and experimental ( ) ranges overlapping.
Abstract: A combined numerical and experimental study examining vortex-induced vibration (VIV) of a neutrally buoyant tethered sphere has been undertaken. The study covered the Reynolds-number range , with the numerical ( ) and experimental ( ) ranges overlapping. Neutral buoyancy was chosen to eliminate one parameter, i.e. the influence of gravity, on the VIV behaviour, although, of course, the effect of added mass remains. The tether length was also chosen to be sufficiently long so that, to a good approximation, the sphere was constrained to move within a plane. Seven broad but relatively distinct sphere oscillation and wake states could be distinguished. For regime I, the wake is steady and axisymmetric, and it undergoes transition to a steady two-tailed wake in regime II at . Those regimes are directly analogous to those of a fixed sphere. Once the sphere begins to vibrate at in regime III, the wake behaviour is distinct from the fixed-sphere wake. Initially the vibration frequency of the sphere is half the shedding frequency in the wake, with the latter consistent with the fixed-sphere wake frequency. The sphere vibration is not purely periodic but modulated over several base periods. However, at slightly higher Reynolds numbers ( ), planar symmetry is broken, and the vibration shifts to the planar normal (or azimuthal) direction, and becomes completely azimuthal at the start of regime IV at . In comparison, for a fixed sphere, planar symmetry is broken at a much higher Reynolds number of . Interestingly, planar symmetry returns to the wake for , in regime V, for which the oscillations are again radial, and is maintained until or higher. At the same time, the characteristic vortex loops in the wake become symmetrical, i.e. two-sided. For , in regime VI, the trajectory of the sphere becomes irregular, possibly chaotic. That state is maintained over the remaining Reynolds-number range simulated numerically ( ). Experiments overlapping this Reynolds-number range confirm the amplitude radial oscillations in regime V and the chaotic wandering for regime VI. At still higher Reynolds numbers of , in regime VII, the trajectories evolve to quasi-circular orbits about the neutral point, with the orbital radius increasing as the Reynolds number is increased. At , the orbital diameter reaches approximately one sphere diameter. Of interest, this transition sequence is distinct from that for a vertically tethered heavy sphere, which undergoes transition to quasi-circular orbits beyond .

Journal ArticleDOI
TL;DR: In this article, an experimental investigation of a low aspect ratio rectangular membrane wing with excess length was presented at angles of attack ranging from 0° to 25° at Reynolds number of 48,700.

Journal ArticleDOI
TL;DR: In this article, the 2D vortex-induced vibration of a circular cylinder in oscillatory flow is investigated numerically for the Keulegan-Carpenter (KC) numbers of 10, 20 and 40 and the Reynolds numbers ranging from 308 to 9240.

Journal ArticleDOI
TL;DR: In this article, the authors studied the fluid-structure interaction of an elastically mounted square cross-section cylinder immersed in a free stream, where the crosssection is mounted such that its sides are at 45° to the free stream direction, in a diamond configuration, and its motion is constrained to the transverse direction relative to the flow direction.

Journal ArticleDOI
TL;DR: In this paper, the results from in-water towing-tank experiments on the vortex-excited vibrations of tapered circular cylinders in a uniform flow are reported and discussed.

Journal ArticleDOI
TL;DR: In this paper, the authors considered the flow around two circular cylinders of equal diameter placed in tandem with respect to the incident uniform flow, and performed two-and three-dimensional simulations of this flow using a Spectral/hp element method to discretise the flow equations, coupled to a simple Newmark integration routine that solves the equation of the dynamics of the cylinder.

Journal ArticleDOI
TL;DR: In this article, a lumped parameter model for vortex-induced vibrations is proposed to study the two degree of freedom (dof) structural oscillator and the effect of freedom to move in this rotational degree offreedom is exploited to our advantage by applying it to the VIVACE (Vortex induced vibration aquatic clean energy) design which was originally proposed by Bernitsas et al. (2008).

Journal ArticleDOI
TL;DR: In this article, the shell side flow-induced vibration of the conical spiral tube bundle is experimentally investigated and the experiment table was built and the operational modes, the vibration parameters of the tube bundle were analyzed.
Abstract: Conical spiral tube bundles are widely used in enhancing the heat transfer via the flow-induced vibration in heat exchangers. The shell side flow-induced vibration of the conical spiral tube bundle is experimentally investigated in this paper. The experiment table was built and the operational modes, the vibration parameters of the tube bundle were analyzed. The results show that, the operational mode frequencies of the conical spiral tube are decreased as the shell-side fluid flow velocity increases, especially for the first order frequency. Within the parameter range of this experiment, the real working frequency of the conical spiral tube is between the 1st and the 2nd operational modes, and the free end vibration amplitude of the tube bundle increases greatly when the shell side fluid flow velocity exceeds a critical value.

Book ChapterDOI
03 Apr 2013
TL;DR: The cable-stayed bridges have been known to be susceptible to excitations, especially during construction, wind, and rain-wind conditions as discussed by the authors, especially during wind, rain and rain wind conditions.
Abstract: Introduction Cable-stayed bridges have been firmly established as the most efficient and cost effective structural form in the 500-ft to 1500-ft span range. With this widespread popularity of cable-stayed bridges around the world, increasingly longer spans are being constructed employing increasingly longer stay cables. The stay cables are laterally flexible structural members with very low fundamental frequency and very little inherent damping. For this reason, the stay cables have been known to be susceptible to excitations, especially during construction, wind, and rain-wind conditions.