Identification of response branches for oscillators with curved and straight contours executing VIV

Kumar, Deepak; Singh, Amit; Sen, Sandeep

doi:10.1016/j.oceaneng.2018.07.010

Cited by 21 publications

(5 citation statements)

References 21 publications

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“…Instead, the normalized vibration frequency () should be a better choice to identify the response branches and transitions (Kumar et al. 2018). As shown in the inset of figure 3( b ), according to the variation with , two branches, following the terminology in the VIV of an isolated circular cylinder (Williamson & Govardhan 2004), are identified.…”

Section: Structural Responsesmentioning

confidence: 99%

“…However, we can see that if only the behaviour of the amplitudes with U * is considered, it is not easy to differentiate response branches because of the smooth transitions. Instead, the normalized vibration frequency (f v /f n ) should be a better choice to identify the response branches and transitions (Kumar et al 2018). As shown in the inset of figure 3(b), according to the f v /f n variation with U * , two branches, following the terminology in the VIV of an isolated circular cylinder (Williamson & Govardhan 2004), are identified.…”

Section: Regime I: Typical Vivmentioning

confidence: 99%

“…typical VIV, small-amplitude VIV, transition response I and II, combined VIV and galloping, and pure galloping, were highlighted. Kumar, Singh & Sen (2018) numerically studied the VIV of a truncated circular cylinder that closely approximates a D-section prism at and found that although the amplitudes are slightly smaller than those of a circular cylinder, the response of the truncated cylinder shows branches similar to those of the circular cylinder. However, as the truncated part enlarges, the vibration amplitudes deviate from those of the circular cylinder significantly (Esmaeili, Rabiee & Bayandor 2020).…”

Section: Introductionmentioning

confidence: 99%

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Flow-induced vibrations of a D-section prism at a low Reynolds number

Chen

Alam

et al. 2022

J. Fluid Mech.

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This paper presents the response and the wake modes of a freely vibrating D-section prism with varying angles of attack ( $\alpha = 0^\circ \text {--}180^\circ$ ) and reduced velocity ( $U^* = 2\text {--}20$ ) by a numerical investigation. The Reynolds number, based on the effective diameter, is fixed at 100. The vibration of the prism is allowed only in the transverse direction. We found six types of response with increasing angle of attack: typical vortex-induced vibration (VIV) at $\alpha = 0^\circ \text {--}35^\circ$ ; extended VIV at $\alpha = 40^\circ \text {--}65^\circ$ ; combined VIV and galloping at $\alpha = 70^\circ \text {--}80^\circ$ ; narrowed VIV at $\alpha = 85^\circ \text {--}150^\circ$ ; transition response, from narrowed VIV to pure galloping, at $\alpha = 155^\circ \text {--}160^\circ$ ; and pure galloping at $\alpha = 165^\circ \text {--}180^\circ$ . The typical and narrowed VIVs are characterized by linearly increasing normalized vibration frequency with increasing $U^*$ , which is attributed to the stationary separation points of the boundary layer. On the other hand, in the extended VIV, the vortex shedding frequency matches the natural frequency in a large $U^*$ range with increasing $\alpha$ generally. The galloping is characterized by monotonically increasing amplitude with enlarging $U^*$ , with the largest amplitude being $A^* = 3.2$ . For the combined VIV and galloping, the vibration amplitude is marginal in the VIV branch while it significantly increases with $U^*$ in the galloping branch. In the transition from narrowed VIV to pure galloping, the vibration frequency shows a galloping-like feature, but the amplitude does not monotonically increase with increasing $U^*$ . Moreover, a partition of the wake modes in the $U^*$ – $\alpha$ parametric plane is presented, and the flow physics is elucidated through time variations of the displacement, drag and lift coefficients and vortex dynamics. The angle-of-attack range of galloping is largely predicted by performing a quasi-steady analysis of the galloping instability. Finally, the effects of $m^*$ and ${\textit {Re}}$ , the roles of afterbody and the roles of separation point in determining vibration responses and vortex shedding frequency are further discussed.

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Section: Structural Responsesmentioning

confidence: 99%

Section: Regime I: Typical Vivmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Flow-induced vibrations of a D-section prism at a low Reynolds number

Chen

Alam

et al. 2022

J. Fluid Mech.

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“…However, an exception is observed at U * = 3.5 where the prism vibration is quasi-periodic, involving a beat-like phenomenon (figure 6a). At this U * , two incommensurate frequencies are identified in the displacements, one corresponding to the vibration frequency while the other corresponding to the natural frequency of the prism, and they have comparable amplitudes (Navrose et al 2014;Kumar, Singh & Sen 2018;Chen et al 2022b). Cheng et al (2022) observed that with this trait, the two frequencies compete with each other in a balanced way.…”

Section: Group 1: Vivmentioning

confidence: 98%

“…At this , two incommensurate frequencies are identified in the displacements, one corresponding to the vibration frequency while the other corresponding to the natural frequency of the prism, and they have comparable amplitudes (Navrose et al. 2014; Kumar, Singh & Sen 2018; Chen et al. 2022 b ).…”

Section: Structural Responsesmentioning

confidence: 99%

Two-degree-of-freedom flow-induced vibrations of a D-section prism

Chen,

Alam,

et al. 2023

J. Fluid Mech.

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This paper presents a comprehensive study of flow-induced vibrations of a D-section prism with various angles of attack $\alpha$ ( $= 0^{\circ }\unicode{x2013}180^{\circ }$ ) and reduced velocity $U^*$ (= 2–20) via direct numerical simulations at a Reynolds number ${Re} = 100$ . The prism is allowed to vibrate in both streamwise and transverse directions. Based on the characteristics of vibration amplitudes and frequencies, the responses are classified into nine different regimes: typical VIV regime ( $\alpha = 0^{\circ }\unicode{x2013}30^{\circ }$ ), hysteretic VIV regime ( $\alpha = 35^{\circ }\unicode{x2013}45^{\circ }$ ), extended VIV regime ( $\alpha = 50^{\circ }\unicode{x2013}55^{\circ }$ ), first transition response regime ( $\alpha = 60^{\circ }\unicode{x2013}65^{\circ }$ ), dual galloping regime ( $\alpha = 70^{\circ }$ ), combined VIV and galloping regime ( $\alpha = 75^{\circ }\unicode{x2013}80^{\circ }$ ), narrowed VIV regime ( $\alpha = 85^{\circ }\unicode{x2013}145^{\circ }$ ), second transition response regime ( $\alpha = 150^{\circ }\unicode{x2013}160^{\circ }$ ) and transverse-only galloping regime ( ${\alpha = 165^{\circ }\unicode{x2013}180^{\circ }}$ ). In the typical and narrowed VIV regimes, the vibration frequencies linearly increase with increasing $U^*$ . In the hysteretic and extended VIV regimes, the vibration amplitudes are large in a wider range of $U^*$ as a result of the closeness of the vortex shedding frequency to the natural frequency of the prism because of the shear layer reattachment and separation point movement. In the two galloping regimes, the transverse amplitude keeps increasing with $U^*$ while the streamwise amplitude stays small or monotonically increases with increasing $U^*$ . In the combined VIV and galloping regime, the vibration amplitude is relatively small in the VIV region while drastically increasing with increasing $U^*$ in the galloping region. In the transition response regimes, the vibration frequencies are galloping-like but the divergent amplitude cannot persist at high $U^*$ . Furthermore, a wake mode map in the examined parametric space is offered. Particular attention is paid to physical mechanisms for hysteresis, dual galloping and flow intermittency. Finally, we probe the dependence of the responses on Reynolds numbers, mass ratios and degrees of freedom, and analyse the roles of the shear layer reattachment and separation point movement in the appearance of multiple responses.

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Vortex-induced vibrations of tandem diamond cylinders: A novel lock-in behavior

Kumar

Sourav

2023

International Journal of Mechanical Sciences

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Identification of response branches for oscillators with curved and straight contours executing VIV

Cited by 21 publications

References 21 publications

Flow-induced vibrations of a D-section prism at a low Reynolds number

Flow-induced vibrations of a D-section prism at a low Reynolds number

Two-degree-of-freedom flow-induced vibrations of a D-section prism

Vortex-induced vibrations of tandem diamond cylinders: A novel lock-in behavior

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