A finite difference solution of the shear flow over a circular cylinder

Lei, Chengwang; Cheng, Liang; Kavanagh, Kieran

doi:10.1016/s0029-8018(98)00050-x

Cited by 75 publications

(88 citation statements)

References 18 publications

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“…In the first branch (β ∈ [0, 0.2]), C x slowly decreases as a function of β. A similar trend was observed by Lei et al (2000), Kang (2006) and Cao et al (2010) in the same range of β, at comparable Reynolds numbers. As the shear parameter is increased above 0.…”

Section: Fluid Forcessupporting

confidence: 85%

“…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%

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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: Fluid Forcessupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Vortex-induced vibrations of a cylinder in planar shear flow

2017

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“…A second-order scheme is used for aIl the time dependent terms. For details of numerical Implementation, readers are refered to Lei et al (1999).…”

Section: Methodsmentioning

confidence: 99%

Numerical modelling oflocal scour around offshore pipelines

Li¹,

Cheng

2000

VIèmes Journées, Caen

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Based on an intensive review on the development of numerical models of local scour below offshore pipelines over the last two decades, a numerical model is developed for predicting the time development of scour hole below a pipeline. The present numerical model solves the flow field using a Large Eddy Simulation (LES) mode!. The morphological change of the seabed is calculated via the continuity equation. The sediment deposition and entrainment rates are Iinked with the concentration of the sediment. The application of the present model to sorne laboratory tests demonstrates the robustness of the present rnodel. RésuméBasé sur une revue intensive du développement des modèles numériques d'étude de l'érosion locale sous des conduits situés en pleine mer, un model numérique a été développé pour prédire le temps de development d'un trou due à l'érosion sous un conduit. Ce modèle numérique, résout le champ d'écoulement en utilisant un modèle "Large Eddy Simulation" (LES). Le changement morphologique du fond marin est calculé à partir de l'équation de continuité. La déposition sédimentaire et le taux d'entraînement sont liés à la concentration sédimentaire. L'application de ce modèle à quelques essais de laboratoire démontre la robustesse du modèle.

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“…Moreover, H = 4π 2 e 4πξ , Re = 2u ∞ a ν , u ∞ is the free-stream velocity, ν is the kinematic viscosity, and the dimensionless time is t = t * u ∞ a . The sketch of shear flow, which shows the change of the velocity in the cross-section plane of the cylinder, with a linear velocity profile u = u ∞ + Gy [43] over a cylinder in two-dimensional domain is shown in Figure 2, where u ∞ is the free-stream velocity at the center-line θ = 0, y is the coordinate in the lateral direction with y = 0 at the center of the cylinder, and G is the lateral velocity gradient. Defining the shear rate K as…”

Section: Governing Equationsmentioning

confidence: 99%

Investigations on the Effects of Vortex-Induced Vibration with Different Distributions of Lorentz Forces

et al. 2017

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Abstract:The control of vortex-induced vibration (VIV) in shear flow with different distributions of Lorentz force is numerically investigated based on the stream function-vorticity equations in the exponential-polar coordinates exerted on moving cylinder for Re = 150. The cylinder motion equation coupled with the fluid, including the mathematical expressions of the lift force coefficient C l , is derived. The initial and boundary conditions as well as the hydrodynamic forces on the surface of cylinder are also formulated. The Lorentz force applied to suppress the VIV has no relationship with the flow field, and involves two categories, i.e., the field Lorentz force and the wall Lorentz force. With the application of symmetrical Lorentz forces, the symmetric field Lorentz force can amplify the drag, suppress the flow separation, decrease the lift fluctuation, and then suppress the VIV while the wall Lorentz force decreases the drag only. With the application of asymmetrical Lorentz forces, besides the above-mentioned effects, the field Lorentz force can increase additional lift induced by shear flow, whereas the wall Lorentz force can counteract the additional lift, which is dominated on the total effect.

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A finite difference solution of the shear flow over a circular cylinder

Cited by 75 publications

References 18 publications

Vortex-induced vibrations of a cylinder in planar shear flow

Vortex-induced vibrations of a cylinder in planar shear flow

Numerical modelling oflocal scour around offshore pipelines

Investigations on the Effects of Vortex-Induced Vibration with Different Distributions of Lorentz Forces

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