Wake dynamics and heuristic modelling in the desynchronization region of 1-DOF VIV

O'Neill, Christopher M.; Riches, Graham; Morton, Chris

doi:10.1016/j.ijheatfluidflow.2020.108729

Cited by 3 publications

(1 citation statement)

References 24 publications

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“…Similarly, Riches et al [31] studied the modes at the initial and upper branches of a 1 DoF system after extracting the snapshots using particle image velocimetry techniques. Recently, O'Neill et al [32] presented the analysis of POD in the de-synchronisation region at Re D = 4000 for a 1 DoF oscillating cylinder. They showed that the coherent motions persist in that region, thus relating the vortex-shedding frequency and the lock-in oscillation frequency of the cylinder.…”

Section: Introductionmentioning

confidence: 99%

On the Wake Dynamics of an Oscillating Cylinder via Proper Orthogonal Decomposition

Eiximeno

Miró

Cajas

et al. 2022

Fluids

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The coherent structures and wake dynamics of a two-degree-of-freedom vibrating cylinder with a low mass ratio at Re=5300 are investigated by means of proper orthogonal decomposition (POD) of a numerical database generated using large-eddy simulations. Two different reduced velocities of U*=3.0 and U*=5.5, which correspond with the initial and super-upper branches, are considered. This is the first time that this kind of analysis is performed in this kind of system in order to understand the role of large coherent motions on the amplification of the forces. In both branches of response, almost 1000 non-correlated in-time velocity fields have been decomposed using the snapshot method. It is seen that a large number of modes is required to represent 95% of the turbulent kinetic energy of the flow, but the first two modes contain a large percentage of the energy as they represent the wake large-scale vortex tubes. The energy dispersion of the high-order modes is attributed to the cylinder movement in the inline and cross-stream directions. Substantially different POD modes have been found in the two branches. While the first six modes resemble those observed in the static cylinder or in the initial branch of a one-degree of freedom cylinder in the initial branch, the modes not only contain information about the wake vortexes in the super-upper branch but also about the formation of the 2T vortex pattern and the Taylor–Görtler structures. It is shown that the 2T vortex pattern is formed by the interplay between the Taylor–Görtler stream-wise vortical structures and the cylinder movement and is responsible for the increase in the lift force and larger elongation in the super-upper branch.

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Section: Introductionmentioning

confidence: 99%

On the Wake Dynamics of an Oscillating Cylinder via Proper Orthogonal Decomposition

Eiximeno

Miró

Cajas

et al. 2022

Fluids

View full text Add to dashboard Cite

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Vortex-induced vibrations in the presence of moderate freestream turbulence

Ramesh,

Morton,

Yarusevych

2024

Physics of Fluids

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The influence of incoming freestream turbulence on an elastically mounted circular cylinder undergoing vortex-induced vibrations is investigated through simultaneous displacement and flow field measurements at a constant Reynolds number of approximately 4400. The results show that the effects of freestream turbulence are more prominent within the lower branch and desynchronization, where earlier desynchronization is observed with elevated freestream turbulence. Conversely, freestream turbulence minimally affects the structure and wake dynamics within the initial and upper branches. A comparison between a stationary cylinder wake and the wake of a cylinder free to vibrate at very low amplitudes reveals that even minor cylinder vibrations (≈ 1% of cylinder diameter) modify the separated shear layer and near wake dynamics, the result of which is a decreased sensitivity of the near wake to freestream turbulence. Proper orthogonal decomposition is used to identify changes in the vortex shedding characteristics that result in earlier desynchronization.

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Vortex-Induced Vibration Performance and Mechanism Analysis of a Suspension Bridge Affected by Water-Filled Barriers

Lang,

Wang,

Liu

et al. 2023

Int. J. Str. Stab. Dyn.

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The existence of water-filled barriers alters the cross-sectional shape of the main girder, which may lead to vortex-induced vibrations (VIVs) in suspension bridges. However, the mechanism and occurrence conditions of VIVs in the main girder that is affected by water-filled barriers are still unclear. To this end, this study investigates the effect of water-filled barriers on the VIV performance of suspension bridges. The evolution of the vortex structure during one VIV cycle and the corresponding pressure variations, including the average and fluctuating values on the surface, were analyzed. Additionally, the spatiotemporal distribution of the surface pressure was studied using proper orthogonal decomposition (POD). The results show that VIV occurs in the main girder when the height of the water-filled barriers exceeds a threshold value of 0.317. Moreover, a significant negative pressure vortex occurred when the barriers were installed. The vortex underwent the following distinct phases in one VIV cycle: generation, separation, reattachment, and shedding. However, the negative pressure vortex behind the barrier did not vary substantially when the water-filled barriers were installed without VIV. Additionally, the average pressure on the surface of the main girder remained constant regardless of the occurrence of VIVs. In the presence of VIVs, the pressure fluctuations became much more pronounced and were mainly concentrated on the top surface and leading edge of the main girder. Additionally, the dominant modes of the pressure variations correlated with the evolution of the vortices and pressure distribution.

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Wake dynamics and heuristic modelling in the desynchronization region of 1-DOF VIV

Cited by 3 publications

References 24 publications

On the Wake Dynamics of an Oscillating Cylinder via Proper Orthogonal Decomposition

On the Wake Dynamics of an Oscillating Cylinder via Proper Orthogonal Decomposition

Vortex-induced vibrations in the presence of moderate freestream turbulence

Vortex-Induced Vibration Performance and Mechanism Analysis of a Suspension Bridge Affected by Water-Filled Barriers

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