On uniform planar shear flow around a circular cylinder at subcritical Reynolds number

Sumner, D.; Akosile, O.O.

doi:10.1016/j.jfluidstructs.2003.08.004

Cited by 58 publications

(74 citation statements)

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“…The case of a fixed circular cylinder placed in planar shear flow has been addressed experimentally Kwon, Sung & Hyun 1992;Sumner & Akosile 2003;Cao et al 2007) and numerically (Jordan & Fromm 1972;Yoshino & Hayashi 1984;Chew, Luo & Cheng 1997;Lei, Cheng & Kavanagh 2000;Kang 2006;Cao et al 2010). These prior studies, which mainly focused on linear shear, quantified the evolution of the vortex shedding frequency and time-averaged fluid forces as functions of the shear parameter (β), defined as the inflow velocity gradient normalized by the cylinder diameter and the oncoming flow velocity at the centre of the body.…”

Section: Introductionmentioning

confidence: 99%

Vortex-induced vibrations of a cylinder in planar shear flow

2017

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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 : 18137 The system composed of a circular cylinder, either fixed or elastically mounted, and immersed in a current linearly sheared in the cross-flow direction, is investigated via numerical simulations. The impact of the shear and associated symmetry breaking are explored over wide ranges of values of the shear parameter (non-dimensional inflow velocity gradient, β ∈ [0, 0.4]) and reduced velocity (inverse of the non-dimensional natural frequency of the oscillator, U * ∈ [2, 14]), at Reynolds number Re = 100; β, U * and Re are based on the inflow velocity at the centre of the body and on its diameter. In the absence of large-amplitude vibrations and in the fixed body case, three successive regimes are identified. Two unsteady flow regimes develop for β ∈ [0, 0.2] (regime L) and β ∈ [0.2, 0.3] (regime H). They differ by the relative influence of the shear, which is found to be limited in regime L. In contrast, the shear leads to a major reconfiguration of the wake (e.g. asymmetric pattern, lower vortex shedding frequency, synchronized oscillation of the saddle point) and a substantial alteration of the fluid forcing in regime H. A steady flow regime (S), characterized by a triangular wake pattern, is uncovered for β > 0.3. Free vibrations of large amplitudes arise in a region of the parameter space that encompasses the entire range of β and a range of U * that widens as β increases; therefore vibrations appear beyond the limit of steady flow in the fixed body case (β = 0.3). Three distinct regimes of the flow-structure system are encountered in this region. In all regimes, body motion and flow unsteadiness are synchronized (lock-in condition). For β ∈ [0, 0.2], in regime VL, the system behaviour remains close to that observed in uniform current. The main impact of the shear concerns the amplification of the in-line response and the transition from figure-eight to ellipsoidal orbits. For β ∈ [0.2, 0.4], the system exhibits two well-defined regimes: VH1 and VH2 in the lower and higher ranges of U * , respectively. Even if the wake patterns, close to the asymmetric pattern observed in regime H, are comparable in both regimes, the properties of the vibrations and fluid forces clearly depart. The responses differ by their spectral contents, i.e. sinusoidal versus multi-harmonic, and their amplitudes are much larger in regime VH1, where the in-line responses reach 2 diameters (0.03 diameters in uniform flow) and the cross-flow responses 1.3 diameters. Aperiodic, intermittent oscillations are found to occur in the transition region between regimes VH1 and VH2; it appears that wake-body synchronization persists in this case.

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Section: Introductionmentioning

confidence: 99%

Vortex-induced vibrations of a cylinder in planar shear flow

2017

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“…The dominant frequency with the flow velocity of 0.2 m/s is 1.27 Hz, which approaches the riser second-order natural frequency. Several studies [5,12] have shown that the "lock-in" phenomenon occurs while the vortex shedding frequency approaches the riser natural frequency. Under this phenomenon, the riser vibrates significantly at its natural frequency in the CF direction.…”

Section: Discussionmentioning

confidence: 99%

“…(11) and (12). The phase angles with the flow velocities of 0.1, 0.2, and 0.3 m/s are 60°, 200°, and 137°, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…They also investigated the wake mode and discovered the "2T" mode. Sumner and Akosile [12] conducted a VIV experiment with Reynolds number ranging from 4×104 to 9×104, and determined that low to moderate shear caused a small increase in the Strouhal number. Chaplin et al [13] conducted a study on the VIV of a vertical tension riser in a stepped current and determined the existence of multi-frequency.…”

Section: Introductionmentioning

confidence: 99%

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Experimental study of vortex-induced vibration for drilling risers under uniform flow current

Mao¹,

Liu²,

Zhou³

et al. 2017

J. vibroeng.

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Abstract. An experiment was conducted in a deep water basin to investigate the vortex-induced vibration mechanism of a drilling riser. Various measurements were obtained by the fiber Bragg grating strain sensors, and data was analyzed by modal analysis method. Results show that the vibration mode of the drilling riser increases with the increasing flow velocity, and the vibration amplitude in the CF direction is larger than that in the IL direction. The vibrations in the CF and IL directions interact and mutually affect each other. The vibration mode in the IL direction is usually larger than that in the CF direction as the dominant vibration frequency is twice of that in the CF direction. Higher stresses may occur rather in the IL direction than in the CF direction. Hence, fatigue induced by the IL direction should also be taken into consideration when analyzing the fatigue life of a drilling riser. The three-time harmonic appears, and the phenomenon becomes more obvious as the flow velocity increased for the effect of the "2T" wake mode under the experiment condition. Displacement trajectories are significantly influenced by dominant vibration frequency and phase angle between the CF and IL directions. Crescent shapes, figure-eight, and inclined figure-eight are appeared in the experiment with the increasing flow velocity.

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“…It was shown by previous investigations on circular cylinders, e.g., Jordan and Fromm (1972), Kiya et al (1980), Kwon et al (1992), Mukhopadhyay et al (1999), Xu and Dalton (2001), Sumner and Akosile (2003), that the flow approaching with linear shear greatly alters the vortex dynamics in the wake, when compared to the uniform flow case. They attributed this phenomenon to the constant vorticity embedded in the free-stream.…”

Section: Introductionmentioning

confidence: 91%

A numerical investigation of wake and mixing layer interactions of flow past a square cylinder

Mushyam

Bergadà

2016

Meccanica

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Aquesta és una còpia de la versió author's final draft d'un article publicat a la revista Meccanica.La publicació final està disponible a Springer a través de http://dx.doi.org/10.1007/s11012-016-0400-8 This is a copy of the author 's final draft version of an article published in the journal Meccanica. Abstract:The aim of the present study is to simulate and analyze the interaction of two dimensional flow past a square cylinder in a laminar regime with an upstream mixing layer developed by an axis symmetrical horizontal splitter plate. The mixing layer is generated upstream of the square cylinder by mixing two uniform streams of fluid with different velocities above and below the splitter plate. A range of upstream domain lengths, distances between the splitter plate and the square cylinder, and upstream velocity ratios between the two streams of fluid are analyzed. Unconfined flow over a square cylinder placed in uniform upstream flow is initially analyzed as it plays a crucial role in understanding the properties of the wake. The results are compared with the existing literature to validate the code developed and they are found to be in very good agreement. It is observed from the present study that at smaller velocity ratios, the vortices shed into the wake consist of both clockwise and anticlockwise moment vortices. As velocity ratio is increased only clockwise moment vortices are shed downstream and anticlockwise vortices are shed as Kelvin-Helmholtz instabilities. In all simulations undertaken the same phenomena is observed independent of the upstream Reynolds number, indicating that velocity ratio is a primary parameter influencing the flow. Different instability modes were observed and they were highly dependent on the upstream velocity ratio.

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On uniform planar shear flow around a circular cylinder at subcritical Reynolds number

Cited by 58 publications

References 30 publications

Vortex-induced vibrations of a cylinder in planar shear flow

Vortex-induced vibrations of a cylinder in planar shear flow

Experimental study of vortex-induced vibration for drilling risers under uniform flow current

A numerical investigation of wake and mixing layer interactions of flow past a square cylinder

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