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.

Turbulent vortex streets and the entrainment mechanism of the turbulent wake

1974 ◽  
Vol 62 (1) ◽  
pp. 11-31 ◽  
Author(s):  
Demosthenes D. Papailiou ◽  
Paul S. Lykoudis
Keyword(s):  
Vortex Shedding ◽  
Reynolds Numbers ◽  
Turbulent Wake ◽  
Vortex Street ◽  
Experimental Measurements ◽  
Formation Region ◽  
Turbulent Vortex ◽  
Geometrical Characteristics ◽  
Vortex Streets ◽  
Longitudinal Distance

The results of an experimental investigation of a turbulent vortex street in the range 103 [lsim ] Re [lsim ] 2 × 104 are presented. The vortex street was created by the motion of a circular cylinder in a motionless fluid (mercury). Photographs obtained showed that the turbulent street, created by the vortex shedding behind the cylinder, persisted at longer downstream distances and higher Reynolds numbers than previously reported in the literature. A theory was developed to account for the experimental measurements pertaining to the change of the geometrical characteristics, h (distance between the two rows of vortices) and α (longitudinal distance between two consecutive vortices on the same row), of the street in the downstream direction. The implications of the structure of the vortex street on the entrainment mechanism of the turbulent wake are discussed. Some observations of the flow in the formation region of the vortices are discussed in relation to existing work.

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.

Flow Induced Acoustic Resonance and Vortex Shedding From Staggered Tube Banks

2003 ◽  
Author(s):  
Hiromitsu Hamakawa ◽  
Tohru Fukano ◽  
Eiichi Nishida
Keyword(s):  
Natural Frequency ◽  
Vortex Shedding ◽  
Velocity Fluctuation ◽  
Sound Pressure ◽  
Coherence Function ◽  
Acoustic Resonance ◽  
Velocity Fluctuations ◽  
Commercial Use ◽  
Pitch Ratio ◽  
Tube Banks

In the present paper our attention is focused on the relation between the vortex shedding phenomena and acoustic resonance in tube banks. We measured a spectrum, coherence function, phase delay of velocity fluctuations in the tube banks and sound pressure level at the duct exit. A model of tube banks had used the same pitch ratio as that of a boiler heat exchanger of a commercial use. As a result, we found three types of vortex shedding with different Strouhal number, 0.29, 0.22 and 0.19. The vortex shedding of St = 0.29 and 0.22 were generated inside of the tube banks. On the other hand St = 0.22 and 0.19 were in the wake of the last row of the tube banks. The velocity fluctuation and the periodicity of the vortex shedding were the most intense in the wake of the second row of the tube banks in whole area of the tube banks. When acoustic resonance generated at the natural frequency of the duct, 342.5Hz, at a gap velocity of 39.2m/s, we found two types of vortex shedding with different frequencies, mainly about 342.5Hz (St = 0.29) and 262.5Hz (St = 0.22), inside of the tube banks. The amplitude of velocity fluctuation due to the vortex shedding became large in accordance with the generation of the acoustic resonance which has the fundamental natural frequency of the acoustic resonance in the transverse direction of the duct.

On the existence of multiple Kármán vortex-street modes

1973 ◽  
Vol 61 (1) ◽  
pp. 199-205 ◽  
Author(s):  
D. Weihs
Keyword(s):  
Vortex Shedding ◽  
Vortex Street ◽  
Multiple Modes ◽  
Karman Vortex Street ◽  
Vortex Streets ◽  
Kármán Vortex Street ◽  
Karman Vortex

An inviscid Kármán-type vortex-shedding model is employed to show that multiple modes of vortex streets are possible, for flow around a given obstacle. This is in confirmation of various experimental observations in recent years, which were challenged by opposing claims that these were due to experimental inaccuracies.

Wake Frequency Analysis of a Plunging Airfoil with Trailing-Edge Strips

2012 ◽  
Vol 225 ◽  
pp. 3-7
Author(s):  
Fariba Ajalli ◽  
Mahmoud Mani ◽  
Mozhgan Gharakhanlou
Keyword(s):  
Vortex Shedding ◽  
Power Spectra ◽  
Leading Edge ◽  
Hot Wire ◽  
Initial Angle ◽  
Trailing Edge ◽  
Wake Structure ◽  
Velocity Defect ◽  
Edge Vortex ◽  
Dominant Frequencies

Experimental measurements were conducted on a plunging Eppler 361 strip flapped airfoil to study wake structure in the wake. The heights of strip flap were 2.6% and 3.3% chord. The velocity in the wake was measured by hot-wire anemometry. It was found that the trailing-edge strip had different effects on the plunging wake profile during the oscillation cycle. At initial angle of 0 degree, the trailing-edge strip causes more velocity defect in the oscillation phases of 180º and 270º. At high initial angle 12 degrees, a significant decrease in value of velocity is found at 180º because of the leading edge vortex shedding. The power spectra of dominant frequencies were significantly increased by fitting the strip flap on the plunging airfoil.

Further Evidence for Acoustic Resonance in Full Size Steam Generator and Tubular Heat Exchanger Tube Banks

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Frantisek L. Eisinger ◽  
Robert E. Sullivan
Keyword(s):  
Heat Exchanger ◽  
Steam Generator ◽  
Vortex Shedding ◽  
Acoustic Resonance ◽  
Heat Exchanger Tube ◽  
Tube Bank ◽  
Tubular Heat Exchanger ◽  
Acoustic Modes ◽  
Tube Banks ◽  
Exchanger Tube

Acoustic resonance or acoustic vibration, which develops in flow channels containing a tube bank, is caused by vortex shedding generated by crossflow over the tube bank. Transverse acoustic modes are excited, which are perpendicular to the direction of flow and of the tube axes. For the excitation of the acoustic modes resulting in acoustic resonance, two conditions must be met: (a) The frequency of vortex shedding must coincide with the frequency of the particular acoustic mode to be excited, and (b) there must be sufficient energy available to initiate the vibration. If the frequency coincidence is not satisfied or if the excitation energy is insufficient, the acoustic resonance will not be possible. It is important to define the criteria, which need to be met for the initiation of the acoustic resonance. In this paper, new criteria are developed on the basis of the acoustic particle velocity for the onset of acoustic resonance in steam generator and tubular heat exchanger tube banks.

Experimental Investigations and Numerical Simulations of the Viscous Flow around T-Profiles

2013 ◽  
Vol 332 ◽  
pp. 3-8
Author(s):  
Mihai Schiaua ◽  
Andrei Dragomirescu ◽  
Carmen Anca Safta
Keyword(s):  
Viscous Fluid ◽  
Numerical Simulations ◽  
Viscous Flow ◽  
Vortex Shedding ◽  
Flow Measurement ◽  
Numerical Models ◽  
Vortex Street ◽  
Open Channels ◽  
Experimental Investigations ◽  
Main Interest

This paper investigates both experimentally and numerically the flow of a viscous fluid around T-profiles, i.e. T-shaped bodies, having different geometries. Of main interest it was the vortex shedding behind the T-profiles with an eye towards its application to flow measurement in open channels. Another purpose of the study was to assess to what extent different numerical models can be used to accurately predict the flow in the vortex street behind T-profiles.

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.

The Orbital Movement and the Damping of the Fluidelastic Vibration of Tube Banks Due to Vortex Formation: Part 3—Damping Capability of the Tube Bank Against Vortex-Excited Sonic Vibration in the Fluid Column

1974 ◽  
Vol 96 (3) ◽  
pp. 1072-1075 ◽  
Author(s):  
Y. N. Chen ◽  
W. C. Young
Keyword(s):  
Velocity Distribution ◽  
Vortex Formation ◽  
Tube Bank ◽  
Ideal Case ◽  
Vortex Streets ◽  
Boiler Units ◽  
Tube Banks ◽  
Damping Capability ◽  
Proper Consideration ◽  
The Ideal

The damping criterion previously proposed by Chen 1964/1968 is evaluated with respect to a series of existing units using various fuels. The critical value of this criterion, which was given by Chen as 600 for the ideal case with uniform velocity distribution, has been found to be about 2000 for the tube bank heat exchangers in boiler units. The reason for this difference appears to lie in the degree of uniformity of the velocity distribution over the streaming section. Since the velocity distribution in the boiler units cannot be uniform at all, the vortex streets formed in the tube bank will disturb each other. A large damping will thus arise. The damping criterion can thus be employed to design a sonic vibration-free tube bank through proper consideration of tube spacings, Reynolds number, and Strouhal number.

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.

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