Experimental Flow-Induced Vibration Analysis of the Crossflow Past a Single Cylinder and Pairs of Cylinders in Tandem and Side-by-Side

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Roberta Fátima Neumeister ◽  
Adriane Prisco Petry ◽  
Sergio Viçosa Möller
Keyword(s):  
Vibration Amplitude ◽  
Damping Ratio ◽  
Sudden Increase ◽  
Blockage Ratio ◽  
Flow Induced Vibration ◽  
Single Cylinder ◽  
Reference Velocity ◽  
Continuous Wavelets ◽  
Constant Height ◽  
Spacing Ratio

Abstract Flow-induced vibration of a single cylinder and two cylinders in tandem and side-by-side configurations is experimentally investigated in this paper in the subcritical regime. The natural frequency of the system varied from 8.8 Hz to 46.2 Hz. The mass ratio, m*, ranged between 158 and 643 while the damping ratio, ζ, between 0.0005 and 0.009. The pairs of cylinders present a spacing ratio of 1.26 (P/D and L/D). In all cases, one and both cylinders (BV) were free to vibrate. Experiments were performed in an aerodynamic channel with a constant height and a variable width, for the evaluation of the influence of the blockage ratio (BR), using accelerometers and hot wire anemometry. The reference velocity, measured at the entrance of the test section was used to calculate the reduced velocity, Vr = U/fnD, with values from 4 to 132 and the Reynolds number between 3 × 103 and 8 × 104. The root-mean-square-values of the displacement amplitudes, Y/D, were obtained through the integration of the acceleration signals. Fourier and continuous wavelets were employed in the analysis. For a single cylinder free to vibrate, the higher amplitudes occur at two distinct reduced velocities, associated with the vibration modes of the cylinder. The vibration amplitude of a single cylinder increased as the blockage ratio increased, decreasing for the highest blockage ratio investigated. For the case of cylinders in tandem, the presence of the fixed cylinder in the wake of the cylinder free to vibrate amplifies the vibration response at high reduced velocities. When the blockage ratio is increased, a sudden increase in the vibration amplitude is observed. When both cylinders are free to vibrate, the relation between the natural frequencies of both cylinders influences the response amplitudes. In the case with two cylinders side-by-side, the vibration amplitude remains similar to a single cylinder, but when both cylinders are free to vibrate, the presence and the influence of flow bistability is observed.

Wavelet Analysis of FIV Response for Single Cylinder and Pairs of Cylinders in Tandem and Side-by-Side

2019 ◽  
Author(s):  
Roberta Fátima Neumeister ◽  
Adriane Prisco Petry ◽  
Sergio Viçosa Möller
Keyword(s):  
Test Section ◽  
Longitudinal Vibration ◽  
Damping Ratio ◽  
Small Variation ◽  
Vibration Modes ◽  
Flow Induced Vibration ◽  
Single Cylinder ◽  
Continuous Wavelets ◽  
Acceleration Signals ◽  
Space Ratio

Abstract Flow induced vibration of a single cylinder and two cylinders assembled in the configurations tandem and side-by-side are experimentally investigated in the present study. The rigid cylinder free to vibrate is fixed in two blades, forming two different configurations, to allow transversal and longitudinal vibration, respectively. The mass ratio, m* ranged between 158 and 643 while the damping ratio, ζ, ranged between 0.0006 and 0.005. The pairs of cylinders present a space ratio of 1.26 (P/D and L/D) and one of the cylinders is fixed while the second one is free to vibrate. The aerodynamic channel used in the analysis presents test section with 0.146m height and 0.193m width, the study is executed using accelerometer and hot wire anemometry. The velocity on the test section is varied and generates reduced velocity, Vr = U/fnD, between 4 and 30. The displacement amplitudes, Y/D, are obtained using integration of the acceleration signals, and the root mean square results are adopted. Fourier spectral analysis and continuous wavelets are employed in the analysis of acceleration and velocity signals. The higher amplitudes happen in two distinct reduced velocities and were associated with the vibration modes of the cylinder free to vibrate. In the case with two cylinders side-by-side the amplitude is higher and present small variation on the reduced velocity of occurrence in comparison with single cylinder. For the case with cylinders in tandem the presence of the cylinder in the wake of the cylinder free to vibrate generated amplification of the response in high reduced velocities.

scholarly journals Effects of Mass and Damping on Flow-Induced Vibration of a Cylinder Interacting with the Wake of Another Cylinder at High Reduced Velocities

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 5148
Author(s):  
Md. Mahbub Alam
Keyword(s):  
Reynolds Number ◽  
Vibration Amplitude ◽  
Amplitude Ratio ◽  
Damping Ratio ◽  
Shear Layers ◽  
Mass Ratio ◽  
Flow Induced Vibration ◽  
Flow Induced Vibrations ◽  
Unique Parameter

Flow-induced vibration is a canonical issue in various engineering fields, leading to fatigue or immediate damage to structures. This paper numerically investigates flow-induced vibrations of a cylinder interacting with the wake of another cylinder at a Reynolds number Re = 150. It sheds light on the effects of mass ratio m*, damping ratio, and mass-damping ratio m*ζ on vibration amplitude ratio A/D at different reduced velocities Ur and cylinder spacing ratios L/D = 1.5 and 3.0. A couple of interesting observations are made. The m* has a greater influence on A/D than ζ although both m* and ζ cause reductions in A/D. The m* effect on A/D is strong for m* = 2–16 but weak for m* > 16. As opposed to a single isolated cylinder case, the mass-damping m*ζ is not found to be a unique parameter for a cylinder oscillating in a wake. The vortices in the wake decay rapidly at small ζ. Alternate reattachment of the gap shear layers on the wake cylinder fuels the vibration of the wake cylinder for L/D = 1.5 while the impingement and switch of the gap vortices do the same for L/D = 3.0.

Numerical simulations of flow field and flow-induced vibration in rectangular channel with single cylinder

2021 ◽  
Vol 385 ◽  
pp. 111551
Author(s):  
Yonghui Guo ◽  
Xiaochang Li ◽  
Ju Liu ◽  
Guangliang Chen ◽  
Qiang Zhao ◽  
...  
Keyword(s):  
Flow Field ◽  
Numerical Simulations ◽  
Rectangular Channel ◽  
Flow Induced Vibration ◽  
Single Cylinder

A Study on Leakage Flow Induced Vibration From Engineering Viewpoint

2015 ◽  
Author(s):  
Fumio Inada
Keyword(s):  
Damping Ratio ◽  
Axial Flow ◽  
Engineering System ◽  
Dimensional System ◽  
Leakage Flow ◽  
Fluid Inertia ◽  
Flow Induced Vibration ◽  
One Dimensional ◽  
Annular Gap ◽  
Excited Vibration

Leakage-flow-induced vibration for a relatively short gap is studied analytically to provide useful information to design structures that include a leakage flow. The relationship between the analysis of a one-dimensional system and that of an annular gap is explained first. Then, the mechanism of flutter-type instability is reproduced from previous study after correcting an error. Finally, the self-excited vibration potential of an engineering system is shown from sample calculations. It is shown that an axial flow becomes dominant in the short-gap approximation, and in this case, the analysis of a one-dimensional flow can be expanded to that of an annular flow. The result that negative damping can occur in the case of a divergent passage owing to the delay induced by fluid inertia was obtained from a previous study. It was suggested analytically that the damping ratio could become negative and its absolute value could become more than 10% in a system that is frequently encountered in a plant, if the natural frequency decreases. The value could be sufficient to generate self-excited vibration.

Flow-Induced Vibration Responses of U-Tube Bundle in Air-Water Flow

2007 ◽  
Author(s):  
In-Cheol Chu ◽  
Heung June Chung ◽  
Chang Hee Lee ◽  
Hyung Hyun Byun ◽  
Moo Yong Kim
Keyword(s):  
Steam Generator ◽  
Two Phase Flow ◽  
Tube Bundle ◽  
Damping Ratio ◽  
Geometrical Parameters ◽  
Phase Flow ◽  
Elastic Instability ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Vibration Responses

In the present study, a series of experiments have been performed to investigate a fluid-elastic instability of a nuclear steam generator U-tube bundle in an air-water two-phase flow condition. A total of 39 U-tubes are arranged in a rotated square array with a pitch-to-diameter ratio of 1.633. The diameter and other geometrical parameters of U-bend region are the same to those of an actual steam generator, but the vertical length of U-tubes are reduced to 2-span in contrast to 9-span of an actual steam generator. The following parameters were experimentally measured to evaluate a fluid-elastic instability of U-tube bundles in a two-phase flow: a general tube vibration response, a critical gap velocity, a damping ratio and a hydrodynamic mass. Based on the experimental measurements, the instability factor, K, of Connors’ relation was preliminary assessed with some assumptions on the velocity and density profiles of the two-phase flow.

Towards Understanding Two-Phase Flow Induced Vibration of Piping Structure With a U-Bend

2019 ◽  
Author(s):  
Olufemi E. Bamidele ◽  
Wael H. Ahmed ◽  
Marwan Hassan
Keyword(s):  
Void Fraction ◽  
Vibration Amplitude ◽  
Two Phase Flow ◽  
Bubbly Flow ◽  
Phase Flow ◽  
Flow Conditions ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Void Fractions ◽  
Flow Induced Vibrations

Abstract The current work investigates two-phase flow induced vibrations in 90° U-bend. The two-phase induced vibration of the structure was investigated in the vertical, horizontal and axial directions for various flow patterns from bubbly flow to wavy and annular-dispersed flow. The void fractions at various locations along the piping including the fully developed void fraction and the void fraction at the entrance of the U-bend were fully investigated and correlated with the vibration amplitude. The results show that the excitation forces of the two-phase flow in a piping structure are highly dependent on the flow pattern and the flow conditions upstream of the bend. The fully developed void fraction and slip between phases are important in modelling of forces in U-bends and elbows.

Two Tandem Cylinders With Turbulence Stimulation in FIV Power Conversion: CFD With Experimental Verification of Interaction

2017 ◽  
Author(s):  
Wenjun Ding ◽  
Hai Sun ◽  
Wanhai Xu ◽  
Michael M. Bernitsas
Keyword(s):  
Frequency Response ◽  
Conversion Efficiency ◽  
Stokes Equations ◽  
Damping Ratio ◽  
Power Conversion ◽  
Clean Energy ◽  
Amplitude Response ◽  
Response Frequency ◽  
Tandem Cylinders ◽  
Spacing Ratio

Flow induced vibrations of two rough, rigid, tandem-cylinders on springs are investigated for power conversion for Reynolds number 30,000 ≤ Re ≤ 120,000. Passive turbulence control (PTC) in the form of roughness strips is employed to enhance FIV and increase the power harness efficiency of the VIVACE (Vortex Induced Vibration for Aquatic Clean Energy) converter. Numerical simulations are performed using two-dimensional, Unsteady Reynolds-Averaged Navier-Stokes equations with the Spalart-Allmaras turbulence model. The center-to-center spacing ratio d / D of the two cylinders is set as 2.0 or 2.57 with mass ratio m* = 1.343 , damping ratio ζ = 0.26, and stiffness K = 1,200 N/m. Amplitude response, frequency response, interaction, energy harvesting, and conversion efficiency are presented and discussed. The main conclusions are: (1) In the VIV region at Re = 60,000, the amplitude response, frequency response, harnessed power, and power conversion efficiency of the upstream cylinder is the same for the two spacing ratios. Due to the shedding effect, the motion of the downstream cylinder for spacing ratio d/D = 2.0 is more severely suppressed than spacing ratio d/D = 2.57, which reduces the harnessed power and conversion efficiency for the downstream cylinder. (2) In the galloping region at Re = 110,000, due to the different impingement of the shed vortices on the downstream cylinder, the upstream cylinder harnesses more power and has higher energy conversion efficiency for spacing ratio d/D = 2.0 than d/D = 2.57.

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