Mass ratio effect on vortex-induced vibration for two tandem square cylinders at a low Reynolds number

2021 ◽  
Vol 33 (12) ◽  
pp. 123604
Author(s):  
Tao Qiu ◽  
Weiqun Lin ◽  
Xiaoqing Du ◽  
Yan Zhao
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Mass Ratio ◽  
Vortex Induced Vibration ◽  
Ratio Effect ◽  
Square Cylinders ◽  
Tandem Square Cylinders ◽  
Low Reynolds

Two Degrees of Freedom Vortex-Induced Vibration Responses With Zero Mass and Damping at Low Reynolds Number

2013 ◽  
Author(s):  
Kintak Raymond Yu ◽  
Alexander Hay ◽  
Dominique Pelletier ◽  
Simon Corbeil-Létourneau ◽  
Shahin Ghasemi ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Parameter Space ◽  
Degrees Of Freedom ◽  
Low Reynolds Number ◽  
Mass Ratio ◽  
Vortex Induced Vibration ◽  
Two Degrees Of Freedom ◽  
Zero Mass ◽  
Vortex Induced Vibrations ◽  
Low Reynolds

Vortex-induced vibration is an important phenomenon for offshore engineering. For applications like the piping in the deep water oil exploration projects, the mass ratios can be of order of one [1]. Hence, there is a practical need to understand the effects of low mass ratio on vortex-induced vibrations to enhance design safety. The main purpose of this study is to numerically explore the two degrees of freedom (transverse and streamwise) responses of vortex-induced vibrations of a cylinder at low Reynolds number for the limiting case of zero mass ratio and zero damping. We aim to characterize the responses. In particular, we focus on determining the maximum amplitude values. It is a continuation from the work of Etienne and Pelletier who studied such behaviors at very low Reynolds number (Re < 50) [2]. We investigate the responses in the following parameter space: Reynolds number (75 ≤ Re ≤ 175), reduced velocity (5.0 ≤ Ur ≤ 11.0) and mass ratio (m* = {0, 0.1, 1}) with a fully coupled fluid-structure interaction numerical model based on the finite element method. Our results are generally in accordance with those from previous works for the displacement trajectories, force phase diagram, and the trends in frequency response and oscillation amplitude. The maximum transverse amplitude is found to be around 0.9 in the studied parameter space. In particular, with zero mass ratio, the maximum transverse amplitude starts to occur at values of reduced velocity higher than 6.5 for Reynolds number larger than 150. This is in contrast to the results of Etienne and Pelletier [2] who found that the maximum transverse amplitude always occurs at the reduced velocity of 6.5 for Reynolds number less than 50. Furthermore, with zero mass ratio, the maximum transverse amplitude increases when the Reynolds number increases. This behavior differs from what was suggested by Williamson and Govardhan [3] for a cylinder oscillating only in the transverse direction at Reynolds numbers in the range of 85 to 200. They found that the Reynolds number has no influence on the maximum transverse amplitude. We do not notice any response branching in this parameter space. However, the results in the present work clearly consist of two distinct characteristics. This indicates that the investigated mass ratio values encompass the critical mass ratio; whose value is estimated to be around 0.1 to 0.2.

Model reduction and mechanism for the vortex-induced vibrations of bluff bodies

2017 ◽  
Vol 827 ◽  
pp. 357-393 ◽  
Author(s):  
W. Yao ◽  
R. K. Jaiman
Keyword(s):  
Reynolds Number ◽  
Bluff Body ◽  
Low Reynolds Number ◽  
Smooth Curve ◽  
Bluff Bodies ◽  
Sharp Corner ◽  
Mass Ratio ◽  
Square Cylinder ◽  
Low Reynolds ◽  
Lock In

We present an effective reduced-order model (ROM) technique to couple an incompressible flow with a transversely vibrating bluff body in a state-space format. The ROM of the unsteady wake flow is based on the Navier–Stokes equations and is constructed by means of an eigensystem realization algorithm (ERA). We investigate the underlying mechanism of vortex-induced vibration (VIV) of a circular cylinder at low Reynolds number via linear stability analysis. To understand the frequency lock-in mechanism and self-sustained VIV phenomenon, a systematic analysis is performed by examining the eigenvalue trajectories of the ERA-based ROM for a range of reduced oscillation frequency $(F_{s})$, while maintaining fixed values of the Reynolds number ($Re$) and mass ratio ($m^{\ast }$). The effects of the Reynolds number $Re$, the mass ratio $m^{\ast }$ and the rounding of a square cylinder are examined to generalize the proposed ERA-based ROM for the VIV lock-in analysis. The considered cylinder configurations are a basic square with sharp corners, a circle and three intermediate rounded squares, which are created by varying a single rounding parameter. The results show that the two frequency lock-in regimes, the so-called resonance and flutter, only exist when certain conditions are satisfied, and the regimes have a strong dependence on the shape of the bluff body, the Reynolds number and the mass ratio. In addition, the frequency lock-in during VIV of a square cylinder is found to be dominated by the resonance regime, without any coupled-mode flutter at low Reynolds number. To further discern the influence of geometry on the VIV lock-in mechanism, we consider the smooth curve geometry of an ellipse and two sharp corner geometries of forward triangle and diamond-shaped bluff bodies. While the ellipse and diamond geometries exhibit the flutter and mixed resonance–flutter regimes, the forward triangle undergoes only the flutter-induced lock-in for $30\leqslant Re\leqslant 100$ at $m^{\ast }=10$. In the case of the forward triangle configuration, the ERA-based ROM accurately predicts the low-frequency galloping instability. We observe a kink in the amplitude response associated with 1:3 synchronization, whereby the forward triangular body oscillates at a single dominant frequency but the lift force has a frequency component at three times the body oscillation frequency. Finally, we present a stability phase diagram to summarize the VIV lock-in regimes of the five smooth-curve- and sharp-corner-based bluff bodies. These findings attempt to generalize our understanding of the VIV lock-in mechanism for bluff bodies at low Reynolds number. The proposed ERA-based ROM is found to be accurate, efficient and easy to use for the linear stability analysis of VIV, and it can have a profound impact on the development of control strategies for nonlinear vortex shedding and VIV.

Transverse vortex-induced vibration of a circular cylinder on a viscoelastic support at low Reynolds number

2020 ◽  
Vol 95 ◽  
pp. 102997 ◽  
Author(s):  
Rahul Mishra ◽  
Atul Soti ◽  
Rajneesh Bhardwaj ◽  
Salil S. Kulkarni ◽  
Mark C. Thompson
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Low Reynolds Number ◽  
Vortex Induced Vibration ◽  
Low Reynolds
Sign in / Sign up

Export Citation Format

Share Document