Session: 17-01-01: Research Posters

Paper Number: 149745

149745 - Characterization of Wake Flow Dynamics and Energy Transport in Vortex-Induced Vibration Systems: A Low Reynolds Number Investigation 

 

Vortex Induced Vibration (VIV) is a phenomenon where a structure oscillates within a fluid flow due to vortex formation and shedding. This oscillation can lead to structural fatigue or instability, but it also presents an opportunity for sustainable energy generation. This study explores the flow behavior around an elastically mounted, cylindrical bluff body in low Reynolds number flows (Re < 4000), with the goal of enhancing our understanding and efficiency of VIV systems for innovative fluidic energy harvesters. Energy production in these systems is primarily determined by the amplitude of vibration, which is influenced by both fluidic and structural components. Therefore, a comprehensive understanding and quantification of the fluid-structure interaction in these systems is crucial. We employ Particle Image Velocimetry (PIV), a non-intrusive optical flow measurement technique, to capture wake flow patterns. We also investigate the fluid-structure energy conversion efficiency by calculating the total harvestable energy from the flow and analyzing instantaneous flow patterns. Our findings reveal differences in flow patterns and energy system behaviors between vibrating and non-vibrating cylinders, shedding light on the complex process of energy transfer from the flow to the structure. For this study, VIV regimes of a cylindrical bluff body are categorized into pre-vibration phase, vibration phase (also known as lock-in), and post-vibration phase. The lock-in phenomenon, a synchronization of fluid and structure instabilities, is influenced by structural factors such as damping and fluidic factors such as Reynolds number. Our results indicate that the cylinder vibrates within a Reynolds number range of 1500-3700, peaking at Reynolds number 2300. The vibration occurs in bending mode, about the axis of the aluminum beams. We characterize the global flow fields, Reynolds Shear Stress (RSS), Turbulent Kinetic Energy (TKE), and vorticity distribution of the cylinder during pre-lock-in and post-lock-in by their symmetrical distribution. Flow separation points for both cases are located at both sides of the cylinder midpoint. For pre-lock-in, the saddle point is near Y/D = 3.05, while for post-lock-in, it is further back at Y/D = 4.28. The phase-averaged wake flow characteristics of the cylinder during peak vibration (lock-in) display a pair of asymmetric vortex structures shed from each side of the cylinder. This suggests that the vortices interact in the wake, and the resulting vortex shedding triggers pressure fluctuations that cause the cylinder to vibrate. The differences between the wake patterns of the vibrating and non-vibrating cylinder include the symmetry of wake patterns, location of the saddle point, and higher values of RSS and TKE. The asymmetry of wake patterns arises from vibrational motion, and the saddle point is not easily identifiable in the lock-in flow, indicating that the separated flow does not reattach in the immediate wake region unlike in the non-vibrating case. This research advances our understanding of VIV mechanisms and provides a foundation for optimizing VIV energy harvester arrays. By demonstrating the wake flow characteristics of a single cylinder, we can reason about the optimal placement of cylinders in array configurations.

Presenting Author: Jooi Albano The City College of New York

Presenting Author Biography: Jooi Albano is a Master's student in the City College of New York.

Authors:

Jooi Albano The City College of New York
Ilya Avros Macaulay Honors College at The City College of New York
Andrei Fershalov City College of New York
Pieter Orlandini City College of New York
Niell Elvin City College of New York
Yang Liu The City College of New York