Session: 10.4.2 - Vortex Dynamics II

Paper Number: 155094

155094 - Dynamic Response and Force Analysis of a Vortex Induced Cylinder Vibration: Insights Into Boundary Layer Pressure Distribution, Flow Structures, and Phase Dynamics 

Abstract: 

Vortex-induced vibrations (VIV) of a cylinder represent a critical phenomenon in fluid-solid interaction studies, with applications ranging from energy harvesting to vibration suppression. When a cylinder is allowed to oscillate in the cross-flow direction, pressure fluctuations in the boundary layer, caused by ambient airflow, can induce significant vibration amplitudes under specific conditions. This research focuses on studying the boundary layer pressure distribution and its interaction with the cylinder's dynamic behavior. The study encompasses distinct regimes of VIV: pre-lock-in (no vibration), lock-in (significant vibrations), and post-lock-in (vibration cessation). Key parameters investigated include lift and drag forces, the phase lag between lift force and cylinder movement, and changes in wake structure.

An experimental approach was employed to capture these interactions. Strain gauge measurements were used to track cylinder movement, while multichannel pressure sensors recorded the boundary layer pressure distribution. High-speed camera recordings synchronized with pressure sensors and strain gauges provided visualization of the wake structure and flow dynamics. This combination of methods enabled precise correlation between cylinder motion, pressure fluctuations, and the wake structure’s evolution, offering a comprehensive dataset for understanding fluid-solid interactions.

The results reveal significant changes in drag and lift coefficients during the lock-in regime, emphasizing the complex coupling between fluid flow and the oscillating cylinder. A gradual increase in lift and drag coefficients was observed as the air velocity increased during the system's entry into the lock-in regime (initial branch). A sudden drop in lift and drag coefficients occurred as the airflow velocity exceeded the point of peak vibration amplitude, transitioning the system to the lower branch of vibration. In this regime, the lift and drag coefficients gradually decreased, and the vibrations eventually ceased, marking the post-lock-in regime. Outside the lock-in regime, the lift and drag coefficients remained consistent across both pre-lock-in and post-lock-in phases, indicating distinct behavior in these regions. Additionally, variations in the phase lag between the lift force and cylinder movement were observed, further highlighting the complexities of VIV dynamics.

Flow visualization revealed clear distinctions in wake structure across the VIV regimes, supporting the observed force and vibration data. In the lock-in regime, vortex shedding synchronized with the cylinder’s natural frequency, amplifying the vibration and resulting in a marked increase in lift force. Below or beyond the lock-in regime, vortex shedding became unnoticeable, leading to vibration cessation.

These findings provide critical insights into the behavior of VIV systems. For energy harvesting, understanding the lock-in regime and optimizing parameters can enhance energy capture from ambient airflow. Conversely, for vibration suppression, these results offer a foundation for designing strategies to minimize unwanted oscillations, improving the safety and reliability of structures. This study presents the first systematic collection of cylinder VIV dynamics, including displacements and applied fluid forces, coupled with flow visualization. It provides a valuable experimental dataset for advancing both theoretical modeling and practical applications of vortex-induced vibrations.

Presenting Author: Andrei Fershalov City College of New York

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