Session: 10-04-01: Young Engineer Paper (YEP) Contest Fluids Engineering Division

Paper Number: 145956

145956 - 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 in which a structure in a flowing fluid oscillates due to the formation and shedding of vortices. It could cause structural fatigue or instability, but it can also be used as a method for sustainable energy generation. This study investigates the flow behavior around an elastically mounted, cylindrical bluff body in low Reynolds number (Re < 4000) flows, aiming to improve the understanding and efficiency of VIV systems for novel fluidic energy harvesters.   Since energy production in these systems is dominated by the amplitude of vibration, fully understanding and quantifying the fluid-structure interaction in these systems is critical. In this paper, we focus on analyzing the wake flow characteristics of elastically mounted cylinders in both vibrating and non-vibrating modes, as well as the energy transport during the dynamic processes.

The bluff body under investigation is a 3D printed Polylactic Acid cylinder of diameter 40mm, supported by aluminum beams at both ends.  The cylinder is placed in an open return wind tunnel with a test section of 4 ft by 4 ft and contraction ratio of 9. The Particle Image Velocimetry (PIV) technique, a non-intrusive optical flow measurement technique, is used to study the wake flow characteristics. The illumination is provided by Nd:YAG laser sheet with articulated optical arm, the tracer particles are atomized olive oil and a sCMOS camera is used to capture the flow patterns at high resolutions. The VIV regimes are separated into three subcategories: pre-vibration phase, vibration phase and post-vibration phase. Non-vibrating cylinder pictures are taken at 1 frame per second (FPS), and to overcome the frame rate limitations of the experimental system, phase-locked imaging technique is employed.

For data processing, Proper Orthogonal Decomposition (POD) is performed to ease the analysis of large datasets, and both time averaged and instantaneous data is used to calculate the mean kinetic energy, turbulent kinetic energy (TKE) and Reynolds shear stress to get a comprehensive overview of the turbulent flow characteristics. To find the fluid-structure energy conversion efficiency, total harvestable energy from the flow is calculated and instantaneous harvestable power is found by analyzing the instantaneous flow patterns.

The results show the differences in flow patterns and energy system behaviors between vibrating and non-vibrating cylinders, revealing the intricate process of energy transfer from the flow to the structure. Additionally, we uncover the energy transport dynamics when the system's natural frequency becomes decoupled from the Strouhal frequency at higher Reynolds numbers.

This research not only advances our understanding of VIV mechanisms but also sets the groundwork for future explorations into optimizing VIV energy harvesters, particularly through studies on multiple cylinders in arrays and the inter-cylinder flow dynamics. The findings are relevant to the mechanical engineering community, contributing to the development of more efficient renewable energy technologies.

Presenting Author: Jooi Albano City College of New York

Presenting Author Biography: Jooi is a graduate student in the Department of Mechanical Engineering at The City College of New York. She is working on the flow-structure interactions of aerodynamically coupled oscillators.

Authors:

Jooi Albano 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