Multiple Modes of Vortex-Induced Vibration of a Sphere

Jauvtis, N.; Govardhan, Raghuraman N.; Williamson, C. H. K.

doi:10.1006/jfls.2000.0348

Cited by 64 publications

(89 citation statements)

References 6 publications

(5 reference statements)

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“…This mode cannot be explained as the classical lock-in effect, since between 3 and 8 cycles of vortex shedding occurs for each cycle of sphere motion. For reduced velocities beyond the regime for Mode III, another vibration mode was discovered that grew in amplitude and persisted to the limit of flow speed in the wind tunnel [5]. The sphere dynamics of this Mode IV were characterized by in- Pregnalato [13] numerically found that a buoyant tethered sphere oscillates at large amplitude over a wide range of reduced velocity, which is similar to the previous studies ( [2,21]).…”

Section: Tethered Spheresupporting

confidence: 78%

“…He adopted a spectral element method and a coordinate transform to solve the combined fluid-structure system. Even though the flow is within laminar regime (Re = 500), he observed the Modes I, II and III which are shown in [5].…”

Section: Tethered Spherementioning

confidence: 98%

“…However, it is interesting to note that the oscillation frequency for low mass ratios (m * < 1) at high U * did not correspond to either the natural frequency or the vortex shedding frequency for a fixed sphere. Through wind tunnel experiments, Jauvtis et al [5] were able to study mass ratios between m * = 80 and m * = 940 and reduced velocities in the range of U * = [0, 300]. For the sphere of m * = 80, they found a new mode of vibration (which they define as Mode III) and which extends over a broad regime of U * from 20 to 40.…”

Section: Tethered Spherementioning

confidence: 99%

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Vortex-induced vibration of a neutrally buoyant tethered sphere

2013

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Recent preliminary experiments have indicated that a neutrally buoyant tethered sphere develops a large diameter quasi-circular trajectory, unlike the oscillations observed for non-neutrally buoyant tethered spheres. This shows similarities to the path of buoyant bubbles, which may follow zig-zag and/or helical paths depending on the Reynolds number. The current study explores the behaviour using well resolved numerical simulations. The forces like tension, buoyancy and fluid force are con-

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Section: Tethered Spheresupporting

confidence: 78%

Section: Tethered Spherementioning

confidence: 98%

Section: Tethered Spherementioning

confidence: 99%

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Vortex-induced vibration of a neutrally buoyant tethered sphere

2013

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“…Khalak & Williamson [41] and Feng [37] on the cylinders; Jauvtis et al [44] and Mirauda & Greco [45,46] on the spheres.…”

Section: Dynamic Response In Resonance Conditionsmentioning

confidence: 99%

Flow induced excitation on basic shape structures

Franzetti

Greco

Malavasi

et al. 2006

Vorticity and Turbulence Effects in Fluid Structure Interactions

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The study of flow-induced excitation on structures and obstacles is one of the main topics of fluid dynamics related to the practical interests in a large number of engineering applications e.g. aerodynamic, mechanical, civil, naval, etc. New design and project techniques have offered hazardous solutions, resulting in structures that are even more slender and flexible. This has led to a number of situations of self-excited vibration due to the interaction between flow fields and structures. Forces coming from this mechanism depend upon both the incoming flow and the structure motion, giving rise to a strong non-conservative force field, which may eventually lead to a growing structure motion. The aim of this chapter is to offer an overture about the phenomenon of the fluid-structure interaction. Because of the importance that the cylindrical and spherical shapes have in the practical applications and the generalizations that these shapes allow, in this chapter the fluid-structure interaction is mainly referred to these basic shapes.

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“…So can the structural vibrations of a sphere be suppressed by an imposed rotation once the sphere is free to oscillate? The previous investigations on the VIV of spheres by [2] and [3], revealed that the sphere exhibits two modes of vibration, namely, mode I and mode II when the oscillation frequency is of the order of the static body vortex shedding. They showed that the vortex phase φ v (phase difference between the vortex force and the body displacement) gradually The sphere rotates in the clockwise direction with rotational rate ω.…”

Section: Introductionmentioning

confidence: 98%

Vortex-induced vibration of a transversely rotating sphere

2018

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OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 18563To link to this article : DOI : URL :Any correspondence concerning this service should be sent to the repository administrator: staff-oatao@listes-diff.inp-toulouse.fr AbstractVortex-induced vibration (VIV) of a sphere is one of the most basic fluid-structure interaction problems. Since such vibrations can lead to fatal structural failures, numerous studies have focused on suppressing such flow-induced vibrations. In this study, for the first time, the effect of an imposed transverse rotation on the dynamics of the VIV of an elastically mounted sphere has been investigated. It was observed that the non-dimensional vibration amplitude for a rotating sphere (A * = √ 2y rms /D, where y rms is the root mean square of the displacement in the transverse direction and D = sphere diameter) exhibits a bell-shaped evolution as a function of reduced velocity, similar to the classic VIV response of a non-rotating sphere. The sphere is found to oscillate freely up to a rotation ratio α (ratio of the equatorial velocity of the sphere to the free-stream velocity) close to 0.5. For lower rotation ratios (α ≤ 0.3), the response looks similar to the non-rotating case but with slightly smaller vibration amplitude. For higher α values, the amplitude was found to decrease significantly with the rotation up to α = 0.5. The amplitude dropped drastically after it reached the peak amplitude. This is unlike the VIV response of a rotating circular cylinder where the vibration amplitude increases up to three times the maximum vibration amplitude in the nonrotating case due to a novel asymmetric wake pattern (see [1]).

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Multiple Modes of Vortex-Induced Vibration of a Sphere

Cited by 64 publications

References 6 publications

Vortex-induced vibration of a neutrally buoyant tethered sphere

Vortex-induced vibration of a neutrally buoyant tethered sphere

Flow induced excitation on basic shape structures

Vortex-induced vibration of a transversely rotating sphere

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