Flow-induced vibration suppression for a single cylinder and one-fixed-one-free tandem cylinders with double tail splitter plates

2021 ◽  
Vol 106 ◽  
pp. 103373
Author(s):  
Zhongming Hu ◽  
Jiasong Wang ◽  
Yuankun Sun ◽  
Hanxu Zheng
Keyword(s):  
Vibration Suppression ◽  
Flow Induced Vibration ◽  
Single Cylinder ◽  
Splitter Plates ◽  
Tandem Cylinders

Vibration suppression of wind turbine nacelle with active electromagnetic mass damper systems using adaptive backstepping control

2021 ◽  
pp. 107754632199887
Author(s):  
Sinan Basaran ◽  
Fevzi Cakmak Bolat ◽  
Selim Sivrioglu
Keyword(s):  
Vibration Suppression ◽  
Controller Design ◽  
Wind Load ◽  
Backstepping Control ◽  
Structural Systems ◽  
Adaptive Backstepping ◽  
Electromagnetic Mass ◽  
Flow Induced Vibration ◽  
Adaptive Backstepping Control ◽  
Mass Damper

Many structural systems, such as wind turbines, are exposed to high levels of stress during operation. This is mainly because of the flow-induced vibrations caused by the wind load encountered in every tall structure. Preventing the flow-induced vibration has been an important research area. In this study, an active electromagnetic mass damper system was used to eliminate the vibrations. The position of the stabilizer mass in the active electromagnetic mass damper system was determined according to the displacement information read on the system without using any spring element, unlike any conventional system. The proposed system in this study has a structure that can be implemented as a vibration suppressor in many intelligent structural systems. Two opposing electromagnets were used to determine the instant displacement of the stabilizer mass. The control currents to be given to these electromagnets are determined by using an adaptive backstepping control design. The adaptive controller algorithm can predict the wind load used in the controller design without prior knowledge of the actual wind load. It was observed that the designed active electromagnetic mass damper structure is successful in suppressing system vibrations. As a result, the proposed active electromagnetic mass damper system has been shown to be suitable for structural systems in flow-induced vibration damping.

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

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.

Two Tandem Cylinders With Passive Turbulence Control in Flow-Induced Vibration: Relation of Oscillation Patterns to Frequency Response

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Kai Lan ◽  
Hai Sun ◽  
Michael M. Bernitsas
Keyword(s):  
Frequency Response ◽  
Phase Difference ◽  
Volume Ratio ◽  
Flow Induced Vibration ◽  
Frequency Spectra ◽  
Turbulence Control ◽  
Instantaneous Phase ◽  
Tandem Cylinders ◽  
Flow Induced Vibrations ◽  
The University

Flow-induced vibrations (FIV) are conventionally destructive and should be suppressed. Since 2006, the Marine Renewable Energy Laboratory (MRELab) of the University of Michigan has been studying FIV of multiple cylinders to enhance their response for harnessing hydrokinetic power from ocean, river, and tidal currents. Interactions between multiple cylinders in FIV enable high power-to-volume ratio in a converter consisting of multiple oscillators. This paper investigates experimentally the relation between oscillation patterns and frequency response of two cylinders in tandem. All experiments are conducted in the recirculating channel of the MRELab for 30,000 < Re < 120,000. Phase analysis reveals three dominant patterns of oscillation of two tandem cylinders by calculating the instantaneous phase difference between the two cylinders. This phase difference characterizes each major pattern. Pattern A is characterized by small lead or lag of one cylinder over the other. In pattern B, there is nearly 180 deg out of phase oscillations between the cylinders. In pattern C, the instantaneous phase difference changes continuously from −180 deg to +180 deg. Using frequency spectra and amplitude response, oscillation characteristics of each cylinder are revealed in vortex-induced vibration (VIV) and galloping. Pattern A occurs mostly in galloping when the first cylinder has higher stiffness. Pattern B occurs seldom and typically in the initial VIV branch and transition from VIV to galloping. Pattern C occurs in the upper and lower VIV branches; and in galloping when the lead cylinder has lower stiffness.

The Effect of Sound on Vortex Shedding From Single and Tandem Cylinders

2002 ◽  
Author(s):  
Joseph W. Hall ◽  
Samir Ziada ◽  
David S. Weaver
Keyword(s):  
Vortex Shedding ◽  
Sound Field ◽  
Open Circuit ◽  
Mean Flow ◽  
Number Range ◽  
Single Cylinder ◽  
Tandem Cylinders ◽  
Vortex Shedding Frequency ◽  
The Mean ◽  
Lock In

A single cylinder and two tandem cylinders configurations with longitudinal pitch ratios L/D = 1.75 and 2.5 were rigidly mounted in an open circuit windtunnel and a sound field was applied so that the acoustic particle velocity was normal to both the cylinder axis and the mean flow velocity. Tests were performed for a Reynolds number range of 5000 &lt; ReD &lt; 24000. The effect of sound on the vortex shedding was investigated by instrumenting the cylinders with pressure taps and hot-wire probes. These tests show that applied sound can entrain and shift the natural vortex shedding frequency to the frequency of excitation and produce nonlinearities in the wake. The lock-in envelope for the tandem cylinders is considerably larger than for the single cylinder. The lock-in range for the smaller tandem cylinder spacing (L/D = 1.75) was broader still than either the single cylinder, or the L/D = 2.5 tandem cylinder case.

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