Three-dimensional vorticity measurements in the wake of a yawed circular cylinder

Zhou, Tongming; Wang, H.; Razali, Siti Fatin Mohd; Zhou, Yu; Cheng, Liang

doi:10.1063/1.3291072

Cited by 33 publications

(8 citation statements)

References 43 publications

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“…whereas the root-mean-square lift coefficients violated the IP when θ > 30º for Re = 1000, which was also observed by Lam et al (2010). Zhou et al (2010) observed that the secondary axial vortices were generated in the cylinder wakes and the three dimensionality of the flow was enhanced when θ was larger than 15°. As for a stationary near-wall cylinder, Thapa et al (2014) showed that the IP applied to the flow at the gap ratio of 0.8 better than that at 0.4 for Re = 500.…”

Section: Introductionsupporting

confidence: 64%

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Transverse vortex-induced vibrations of a near-wall cylinder under oblique flows

Zang

Zhou

2017

Journal of Fluids and Structures

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Transverse vortex-induced vibrations (VIVs) of a near-wall cylinder under oblique flows are studied experimentally in a water flume for both increasing and decreasing velocities. The VIV responses and the wake flow patterns around the cylinder are measured with a synchronous measurement system and a PIV. The validity of the Independence Principle (IP) for a cylinder in proximity to a wall is examined in terms of the vibration amplitude, frequency and critical normal reduced velocity. The results show that the combinations of the gap ratio and oblique angle have significant effect on the VIV response of a circular cylinder. The IP is found to be valid in predicting the VIV response for small oblique angles (θ ≤ 30º) and large gap ratios (e/D ≥ 0.8) whereas for large oblique angles (θ > 30º) or small gap ratios (e/D < 0.8), the deviations from the IP are pronounced. The upper and lower critical normal reduced velocities for the onset of VIV are obtained for both increasing and decreasing velocities. Empirical relationships between the correction factor of the critical normal reduced velocity and gap ratio and the oblique angles (θ ≤ 45º) are established. Based on the analyses of the wake flow patterns obtained by PIV, it is found that the difference in the onset of VIV for increasing and decreasing velocities corresponds to different vortex shedding modes at the initial branch: the 2S vortex shedding mode for increasing velocity and the C(2S) mode for decreasing velocity.

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Section: Introductionsupporting

confidence: 64%

“…Particular attention has been paid to the validity of the IP for a stationary wall-free cylinder in estimating the force coefficients and the Strouhal number St (e.g. Ramberg, 1983;Zhao et al, 2009;Lam et al, 2010;Zhou et al, 2010). The Strouhal number is defined as St = f 0 /U 0 D, where f 0 is the vortex shedding frequency.…”

Section: Introductionmentioning

confidence: 99%

Transverse vortex-induced vibrations of a near-wall cylinder under oblique flows

Zang

Zhou

2017

Journal of Fluids and Structures

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“…In the case of rigid and vertical beams (θ ≡ 0), (2.4) reduces to the formulation used in Singh et al (2016). We refer readers to Zhou et al (2010) for a more extensive review of drag on tilted cylinders.…”

Section: Equations For the Fluidmentioning

confidence: 99%

Shear-induced instabilities of flows through submerged vegetation

2020

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We consider the instabilities of flows through a submerged canopy, and show how the full governing equations of the fluid-structure interactions can be reduced to a compact framework that captures many key features of vegetative flow. By modelling the canopy as a collection of homogeneous elastic beams, we predict the steady configuration of the plants in response to a unidirectional flow. This treatment couples the beam equations in the canopy to the fluid momentum equations. Our linear stability analysis suggests new insights into the development of instabilities at the surface of the vegetative region. In particular, we show that shear at the top of the canopy is a dominant factor in determining the onset of instabilities known as monami. Based on numerical and asymptotic analysis of the generalised eigenvalue problem, the system is shown to be stable if the canopy is sufficiently sparse or if the plants are sufficiently flexible.

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“…13 With regard to the variation of Strouhal number St (≡fD/U, where f is the vortex shedding frequency) with Reynolds number, two discontinuities occur when the flow changes from 2D laminar flow to mode A and from mode A to mode B, respectively. 3,7 Flow around an inclined circular cylinder has also been investigated extensively both experimentally [14][15][16][17][18][19] and numerically [20][21][22][23] in the past few decades. In engineering practice, the independence principle (or the cosine law) is commonly employed to predict the hydrodynamic forces and vortex shedding frequency of an inclined circular cylinder.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional transition of vortex shedding flow around a circular cylinder at right and oblique attacks

et al. 2013

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Vortex shedding from an inclined circular cylinder at low values of Reynolds number (Re) is investigated numerically. The aim of the study is to investigate the effect of cylinder oblique angle on the transition from two-dimensionality (2D) to threedimensionality (3D) of the wake flow. The Navier-Stokes equations are solved by the Petrov-Galerkin finite element method for Reynolds numbers ranging from 100 to 1000 and the flow attack angles of α = 0 • and 45 • . For the right attack angle case (α = 0 • ), the predicted wavy spanwise vortices in the early stage of the transition mode A, the vortex dislocation in the late stage of the transition mode A and the streamwise-vortex dominant wake flow structure in the transition mode B are found to agree well with independent experimental observations and measurements. The transition from 2D to 3D at α = 45 • was found distinctively different from that at α = 0 • . For α = 45 • , no clear-cut transition modes are observed. The wake is characterized by wavy spanwise vortices close to the lower boundary of the transition Reynolds number regime, which are similar to those in the early stage of the transition mode A at α = 0 • . The vortex-dislocation in the transition mode A was not observed at α = 45 • . It appears that the fluid flow in the spanwise direction in the primary vortices at α = 45 • does not allow the instability to sustain at a specific spanwise location and trigger the vortex dislocation. Although the wake flow structure is different, the variation of the normal Strouhal number with the normal Reynolds number (both based on the velocity component perpendicular to the cylinder span) at α = 45 • is close to that at α = 0 • in the transitional Reynolds number regime. The root mean square of the lift coefficient normalized by the velocity component perpendicular to the axial direction of the cylinder at α = 45 • is about 20% to 25% larger than that at α = 0 • in the Reynolds number regime between 250 and 500. C 2013 American Institute of Physics. [http://dx.

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Three-dimensional vorticity measurements in the wake of a yawed circular cylinder

Cited by 33 publications

References 43 publications

Transverse vortex-induced vibrations of a near-wall cylinder under oblique flows

Transverse vortex-induced vibrations of a near-wall cylinder under oblique flows

Shear-induced instabilities of flows through submerged vegetation

Three-dimensional transition of vortex shedding flow around a circular cylinder at right and oblique attacks

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