Vortex-induced vibrations of a circular cylinder at low Reynolds numbers

Prasanth, T. K.; Mittal, Sanjay

doi:10.1017/s0022112007009202

Cited by 269 publications

(145 citation statements)

References 38 publications

Supporting

Mentioning

116

Contrasting

Order By: Relevance

“…The cross-flow response of the oscillator may be substantially altered by the addition of the in-line degree of freedom, and in-line vibrations with amplitudes up to half a diameter may be observed. However, at low Reynolds number, the in-line oscillation amplitude remains small, typically one or two orders of magnitude lower than the cross-flow response amplitude for Re < 200 (Prasanth & Mittal 2008). The frequency ratio between the in-line and cross-flow vibrations is generally equal to 2, as expected due to the symmetry of the system.…”

Section: Introductionmentioning

confidence: 71%

Vortex-induced vibrations of a cylinder in planar shear flow

2017

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionmentioning

confidence: 71%

Vortex-induced vibrations of a cylinder in planar shear flow

2017

View full text Add to dashboard Cite

show abstract

“…For low Re there is no upper branch and, therefore, in the present case the cylinder continues to remain on the lower branch. Prasanth and Mittal [25] have suggested a physical mechanism for the phase jump. By decomposing the total lift force into viscous and pressure components at various Re they found that the jump in phase is caused by the pressure component.…”

Section: Effect Of Streamwise Location Of Boundariesmentioning

confidence: 99%

Effect of blockage on free vibration of a circular cylinder at low Re

Prasanth¹,

Mittal²

2008

Numerical Methods in Fluids

Self Cite

View full text Add to dashboard Cite

SUMMARYThe effect of the blockage on vortex-induced vibrations of a circular cylinder of low non-dimensional mass (m * = 10) in the laminar flow regime is investigated in detail. A stabilized space-time finite element formulation is utilized to solve the incompressible flow equations in primitive variables form in two dimensions. The transverse response of the cylinder is found to be hysteretic at both ends of synchronization/lock-in region for 5% blockage. However, for the 1% blockage hysteresis occurs only at the higher Re end of synchronization/lock-in region. Computations are carried out at other blockages to understand its effect on the hysteretic behavior. The hysteresis loop at the lower Re end of the synchronization decreases with decrease in blockage and is completely eliminated for blockage of 2.5% and less. On the other hand, hysteresis persists for all values of blockage at the higher Re end of synchronization/lock-in. Although the peak transverse oscillation amplitude is found to be same for all blockage (∼ 0.6D), the peak value of the aerodynamic coefficients vary significantly with blockage. The r.m.s. values show lesser variation with blockage. The effect of streamwise extent of computational domain on hysteretic behavior is also studied. The phase between the lift force and transverse displacement shows a jump of almost 180 • at, approximately, the middle of the synchronization region. This jump is not hysteretic and is independent of blockage.

show abstract

“…The reduction of resistance or the addition to fatigue of many load cycles at varying amplitudes is expressed by summing up all the values n(σ)/Nσ of all load cycles. The number is called 'Miner number' [5,6]. If Miner number is close to 1 then cracks are expected.…”

Section: Effect Of Fatiguementioning

confidence: 99%

Fatigue Designof Smoke Stacks

Gupta¹,

Bajpai²,

Garg³

2014

Int. Jour. Des. Manf. Tech.

View full text Add to dashboard Cite

As vibrations from vortex-shedding occur at moderate wind speeds, structures undergo a considerable number of stress variations. So risk of fatigue is to be taken into account at the design stage itself. Even if a fatigue analysis is not demanded in the code to be applied, risk of fatigue is to be considered, especially with regard to slender steel chimneys due to larger volumes of material subjected to high stresses. Thus, risk of fatigue which has not been addressed in the Indian context, has been taken care in the present paper. It is envisaged that this formulation will be appropriate for inclusion in Indian codes and standards. As part of the case study, a chimney from an industry having Diesel Power Plant has been undertaken. Fatigue analysis of this chimney has been done and measures to reduce fatigue problem have been suggested.

show abstract

Vortex-induced vibrations of a circular cylinder at low Reynolds numbers

Cited by 269 publications

References 38 publications

Vortex-induced vibrations of a cylinder in planar shear flow

Vortex-induced vibrations of a cylinder in planar shear flow

Effect of blockage on free vibration of a circular cylinder at low Re

Fatigue Designof Smoke Stacks

Contact Info

Product

Resources

About