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Vortex induced vibration (VIV) experienced during flow past a cylinder can reduce equipment performance and in some cases lead to failure. Previous studies have shown that the injection of bubbles in the flow over a cylinder typically leads to a monotonic increase in shedding frequency with void fraction, however, a satisfactory explanation for this phenomenon has not been proposed. Unexplained scatter in the data exists, including that the increase in shedding frequency is not universal. More research is needed to characterize the influence of bubbles on the wake structure, and subsequent shift in shedding frequency. To this aim, the effect of bubbles on the structure of the wake and VIV was examined over two values of Reynolds number, 𝑅𝑒𝐷 = 100, 000 and 160,000. Time-resolved particle image velocimetry (TR-PIV), proper orthogonal decomposition (POD) and spectral proper orthogonal decomposition (SPOD) of the wake structures, vibration of the cylinder, and bubble image velocimetry (BIV) were used to assess the flow topology changes under the influence of gas injection. Using SPOD/POD analysis in the near wake, it was found that the primary Karman shedding frequency decreased with the injection of gas, from a Strouhal number of St = 0.2 to St = 0.17−0.18; the width of the spectral peak was found to increase with void fraction. Notably, the vibration of the cylinder at the primary Karman shedding frequency was suppressed following the injection of gas, even at spanwiseaveraged volumetric qualities below 0.01%. This suppression occurred regardless of if gas was concentrated locally near the centerline of the channel, or along the span. BIV data suggests that gas accumulation in the near wake, driven by the high velocity vertical motion of gas, serves to uncouple the cylinder motion from the formation of the vortex street downstream while promoting faster wake recovery.
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This content will become publicly available on April 1, 2026
Harvesting sustainable energy through vortex-induced vibrations of finite length cylinder
Vortex-induced vibration (VIV) has emerged as a promising method for small-scale energy harvesting. This research explores the key parameters affecting VIV in a cylinder-cantilever beam system within a Reynolds number range of 400–7500. The investigation focused on identifying the airflow velocity thresholds that initiate vibrations, measuring peak vibration amplitudes, and determining the critical airflow velocities where vibrations are maximized. By systematically varying mass, stiffness, and cylinder diameter, we examined their distinct effects on system behavior. Key outcomes indicate that larger cylinder diameters lead to increased vibration amplitudes and broader operational bandwidths, while adding mass reduces the bandwidth. Higher stiffness boosts both the maximum amplitude and bandwidth, shifting these to higher airflow velocities. The lock-in regime was observed to initiate at a Strouhal number (St) between 0.175 and 0.197, with vibration cessation occurring at an approximately consistent Strouhal number for each cylinder diameter. The peak vibration amplitude occurred at St ≈ 0.16, with fluctuations of less than 5% across all models. Additionally, the wake structure behind the cylinder and its behavior across the vibration bandwidth were analyzed using flow visualization techniques. A hot-wire anemometer positioned downstream measured velocity fluctuations from vortex shedding. These findings offer practical insights for optimizing VIV-based energy harvesting, linking wake behavior to amplitude response and power output. This study contributes to the broader understanding of VIV energy harvesters and provides a foundation for validating numerical models and enhancing the efficiency of sustainable energy systems.
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- Award ID(s):
- 2131600
- PAR ID:
- 10620697
- Publisher / Repository:
- AIP
- Date Published:
- Journal Name:
- Physics of Fluids
- Volume:
- 37
- Issue:
- 4
- ISSN:
- 1070-6631
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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