The Orbital Movement and the Damping of the Fluidelastic Vibration of Tube Banks Due to Vortex Formation: Part 1—The Interplay Between the Self-Excited Vibration of the Single Circular Cylinder and the Karman Vortex

1974 ◽  
Vol 96 (3) ◽  
pp. 1060-1064
Author(s):  
Y. N. Chen
Keyword(s):  
Vortex Shedding ◽  
Flow Model ◽  
Vortex Formation ◽  
The Self ◽  
Vortex Street ◽  
Excited Vibration ◽  
Karman Vortex ◽  
Tube Banks ◽  
Lock In ◽  
The Relationship

In the present paper a series of experimental results obtained by several authors on the phenomena of the vortex street behind a vibrating cylinder are analysed. From this we can establish a flow model for the relationship between the vortex shedding, the cylinder movement, the vortex lift and the variation in the position of the separation point. This relationship reveals that a close synchronization of the vortex shedding and the lift generated by it will arise when the flow velocity enters the lock-in region. Furthermore, the flow model will enable us to predict the narrowing of the vortex street shed by a vibrating cylinder for certain Reynolds number ranges. The theory can thus qualitatively explain the corresponding phenomena observed by Koopmann, Griffin and Votaw.

Synchronized Vibrations of a Circular Cylinder in Cross Flow at Supercritical Reynolds Numbers1

2003 ◽  
Vol 125 (1) ◽  
pp. 97-108 ◽  
Author(s):  
Tsutomu Kawamura ◽  
Toshitsugu Nakao ◽  
Masanori Takahashi ◽  
Masaaki Hayashi ◽  
Kouichi Murayama ◽  
...  
Keyword(s):  
Circular Cylinder ◽  
Strouhal Number ◽  
Vortex Shedding ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Excited Vibration ◽  
Karman Vortex ◽  
Lock In

Synchronized vibrations of a circular cylinder in a water cross flow at supercritical Reynolds numbers were measured. Turbulence intensities were varied to investigate the effect of the Strouhal number on the synchronization range. Self-excited vibration in the drag direction due to symmetrical vortex shedding began only when the Strouhal number was about 0.29, at a reduced velocity of 1.1. The reduced velocities at the beginning of lock-in vibrations caused by Karman vortex shedding decreased from 1.5 to 1.1 in the drag direction and from 2.7 to 2.2 in the lift direction, as the Strouhal number increased from 0.29 to 0.48.

An Experimental Study on the Vertical Flow Past a Finite-Length Horizontal Cylinder at Low Reynolds Numbers

2014 ◽  
Vol 493 ◽  
pp. 68-73 ◽  
Author(s):  
Willy Stevanus ◽  
Yi Jiun Peter Lin
Keyword(s):  
Finite Length ◽  
Vortex Shedding ◽  
Vortex Formation ◽  
Reynolds Numbers ◽  
Horizontal Cylinder ◽  
Vortex Street ◽  
Vertical Flow ◽  
Low Reynolds Numbers ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency

The research studies the characteristics of the vertical flow past a finite-length horizontal cylinder at low Reynolds numbers (ReD) from 250 to 1080. The experiments were performed in a vertical closed-loop water tunnel. Flow fields were observed by the particle tracer approach for flow visualization and measured by the Particle Image Velocimetry (P.I.V.) approach for velocity fields. The characteristics of vortex formation in the wake of the finite-length cylinder change at different regions from the tip to the base of it. Near the tip, a pair of vortices in the wake was observed and the size of the vortex increased as the observed section was away from the tip. Around a distance of 3 diameters of the cylinder from its tip, the vortex street in the wake was observed. The characteristics of vortex formation also change with increasing Reynolds numbers. At X/D = -3, a pair of vortices was observed in the wake for ReD = 250, but as the ReD increases the vortex street was observed at the same section. The vortex shedding frequency is analyzed by Fast Fourier Transform (FFT). Experimental results show that the downwash flow affects the vortex shedding frequency even to 5 diameters of the cylinder from its tip. The interaction between the downwash flow and the Von Kármán vortex street in the wake of the cylinder is presented in this paper.

Study on Evaluation of Sound Speed in Duct With Tube Banks

2010 ◽  
Author(s):  
Kunihiko Ishihara
Keyword(s):  
Heat Exchanger ◽  
Resonance Frequency ◽  
Vortex Shedding ◽  
Sound Speed ◽  
Flow Direction ◽  
Fem Analysis ◽  
The Self ◽  
Resonance Phenomenon ◽  
Acoustic Characteristics ◽  
Tube Banks

As tube banks are set in a duct in a boiler and a heat exchanger, the resonance phenomenon or the self sustained tone are generated due to the interference between vortex shedding and the acoustic characteristics of the duct. It is necessary to know the resonance frequency of the duct, namely sound speed, for avoiding any trouble that may arise. In general, it is said that the sound speed decreases in the duct with tube banks and an evaluation formula is given. However, this formula is often used for the perpendicular direction of the flow. We wanted to know whether this formula would be able to be used for the flow direction and for various arrays of patterns or not. In this paper, the applicability of this expression is discussed by using FEM analysis and experiments.

Flow Over the Tip Region of a Flexible Cantilever Wing With the Effect of Angle of Attack

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Ye Hu ◽  
Xiaohui Liu ◽  
Wei Shyy ◽  
Huihe Qiu
Keyword(s):  
Angle Of Attack ◽  
Vortex Street ◽  
Tip Vortex ◽  
Karman Vortex Street ◽  
Wing Model ◽  
Excited Vibration ◽  
Kármán Vortex Street ◽  
Karman Vortex ◽  
Particle Imaging ◽  
Wing Tip

The investigation focused on the conversions of flow structures with a change in angle of attack (AOA) for a flexible cantilever wing, which experienced a self-excited vibration. Stereoscopic particle imaging velocimetry (Stereo-PIV) was utilized to measure the velocity field in the wing-tip region as AOA varied from 0 deg to 12 deg. At the Reynolds number (Re) of 3 × 104, instability waves shedding from the wing were amplified as they propagated and developed into Karman Vortex Street in the far downstream region at low AOAs (AOA = 4 deg and 6 deg). As AOA increased to 8 deg with the wing model was still steady, the Karman Vortex Street no longer existed. The wing started to vibrate at AOA = 10 deg owing to the self-excited vibration, and the Karman Vortex Street appeared again. The inception location of the Karman Vortex Street moved further upstream than in the cases at AOA = 4 deg and 6 deg. A new vortex structure, secondary vortex-pairs, appears outside the main wing-tip vortex (WTV).

The Orbital Movement and the Damping of the Fluidelastic Vibration of Tube Banks Due to Vortex Formation: Part 2—Criterion for the Fluidelastic Orbital Vibration of Tube Arrays

1974 ◽  
Vol 96 (3) ◽  
pp. 1065-1071
Author(s):  
Y. N. Chen
Keyword(s):  
High Speed ◽  
Vortex Formation ◽  
Vortex Pair ◽  
Free Shear Layer ◽  
Vortex Model ◽  
Speed Flow ◽  
Vortex Streets ◽  
Tube Arrays ◽  
Karman Vortex ◽  
Tube Banks

The phenomenon on the tubes in a tube row, which vibrate alternately along the row in the transverse and stream-wise directions, will be explained by a vortex model. This model consists of the symmetrical vortex pair trains behind the stream-wisely vibrating tubes, and the Karman vortex streets behind the transversely vibrating tubes. It will be shown in the paper that the coupling between these two groups of vortex systems can excite the tube arrays to perform this fluidelastic vibration. A criterion for the onset of this orbital movement will be given with the expression ξ = R/Sxt. This criterion predicts a strong fluidelastic vibration for tubes with low transverse tube spacings and low natural flexible frequencies in a high speed flow. The theory leading to this criterion is based on the phenomenon of the variation in the position of the separation point for the free shear layer during the cylinder vibration. A switching of the jet for maintaining the fluidelastic vibration is then a result of this variation.

Sources of Excitation in Tube Banks Due to Vortex Shedding

1986 ◽  
Vol 200 (4) ◽  
pp. 293-301 ◽  
Author(s):  
R S Hill ◽  
K C Shim ◽  
R I Lewis
Keyword(s):  
Vortex Shedding ◽  
Velocity Fluctuation ◽  
Power Spectra ◽  
Vortex Street ◽  
Experimental Investigations ◽  
Causal Mechanism ◽  
Hot Wire ◽  
Tube Bank ◽  
Vortex Streets ◽  
Tube Banks

This paper describes experimental investigations of vortex shedding patterns in staggered and in-line tube banks consisting of four rows with transverse pitch to diameter ratios PT/d of 2.67 and longitudinal pitch to diameter ratios PL/d of 2.31. Single hot wire probes were used to obtain velocity power spectra in order to identify discrete frequencies of velocity fluctuation. Double hot wire probes provided phase correlations which could indicate conclusively the presence of vortex streets. Quite different results were obtained for the staggered and in-line geometries. While vortex street fluctuations were observed in both, an additional higher frequency fluctuation was observed in the staggered tube bank, the causal mechanism for which remains obscure.

The effect of a bevelled trailing edge on vortex shedding and vibration

1973 ◽  
Vol 61 (2) ◽  
pp. 323-335 ◽  
Author(s):  
M. E. Greenway ◽  
C. J. Wood
Keyword(s):  
Vortex Shedding ◽  
Vortex Formation ◽  
Steady Motion ◽  
Visualization Technique ◽  
Rapid Decay ◽  
Formation Region ◽  
Towing Tank ◽  
Excited Vibration ◽  
Trailing Edges ◽  
Circulation Distribution

Experiments using a wind tunnel and a flow visualization technique in a towing tank were conducted to investigate the mechanism of vortex shedding from bevelled trailing edges. These reveal an important difference between the wake structures generated by heaving and steady motion. The suppression of vortex-excited vibration by means of bevelled trailing edges is attributed to the intermittency and rapid decay of the vortex trail resulting from an asymmetric circulation distribution in the vortex formation region.

Vortex Formation in the Wake of a Vibrating, Flexible Cable

1974 ◽  
Vol 96 (4) ◽  
pp. 317-322 ◽  
Author(s):  
S. E. Ramberg ◽  
O. M. Griffin
Keyword(s):  
Vortex Shedding ◽  
Vortex Formation ◽  
Reynolds Numbers ◽  
Hot Wire ◽  
Near Wake ◽  
Formation Region ◽  
Vortex Streets ◽  
Region Length ◽  
Karman Vortex ◽  
Flexible Cables

The von Karman vortex streets formed in the wakes of vibrating, flexible cables were studied using a hot-wire anemometer. All the experiments took place in the flow regime where the vibration and vortex-shedding frequencies lock together, or synchronize, to control the wake formation. Detailed measurements were made of the vortex formation flow for Reynolds numbers between 230 and 650. As in the case of vibrating cylinders, the formation-region length is dependent on a shedding parameter St* related to the natural Strouhal number and the vibrational conditions. Furthermore, the near wake configuration is found to be dependent on the local amplitude of vibration suggesting that the vibrating cylinder rseults are directly applicable in that region.

scholarly journals Design and Analysis of A Vortex Induced Vibration Based Oscillating Free Stream Energy Converter

2021 ◽  
pp. 112-117
Author(s):  
Ratan Kumar Das ◽  
Muhammad Taharat Galib
Keyword(s):  
Vortex Shedding ◽  
Large Scale ◽  
Bluff Body ◽  
Free Stream ◽  
Theoretical Formula ◽  
Pendulum Motion ◽  
Ansys Fluent ◽  
Vortex Induced Vibration ◽  
Karman Vortex ◽  
Lock In

The Kármán Vortex Shedding is one of the special types of vortex that is generated from asymmetric flow separation. For many years engineers tried to suppress the vortex shedding as it brings unnecessary motion to the static members inside the flow field. A converter model is designed and studied to harness the energy associated with this vortex shedding and convert it into usable form rather than suppressing it. It is a bluff body placed on the free stream incurring vortex-induced vibration and giving out a swinging pendulum motion. This motion is utilized to produce electricity. The model is analyzed on the free stream of water and conversion efficiency of 8.9% is achieved. A theoretical formula is derived regarding the force acting on the bluff body during the motion. Various parameters such as aspect ratio, flow velocity, lock-in delay, frequency of oscillation, etc. as well as their relations are studied by simulating the model in ANSYS FLUENT 18.1 for different configurations. From the simulated results it is obvious that as the lift force on the bluff body increases, more power generation is possible. Also, the experimental results paved the way for further study for practical large-scale implementation of the converter.

Sign in / Sign up

Export Citation Format

Share Document