scholarly journals The role of vortex wake dynamics in the flow-induced vibration of tube arrays

2011 ◽  
Vol 27 (5-6) ◽  
pp. 829-837 ◽  
Author(s):  
N.K.-R. Kevlahan
Keyword(s):  
Vortex Wake ◽  
Flow Induced Vibration ◽  
Tube Arrays

The Effect of Flat Bar Supports on Streamwise Fluidelastic Instability in Heat Exchanger Tube Arrays

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Marwan Hassan ◽  
David S. Weaver
Keyword(s):  
Sliding Friction ◽  
Chemical Plants ◽  
Streamwise Direction ◽  
Flow Induced Vibration ◽  
Direction Parallel ◽  
Short Period ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Excitation Mechanisms ◽  
Ambient Turbulence

Flow-induced vibration is an important criterion for the design of heat exchangers in nuclear, fossil, and chemical plants. Of the several known vibration excitation mechanisms, fluidelastic instability (FEI) is the most serious because it can cause tube failures in a relatively short period of time. Traditionally, FEI has been observed to occur in the direction transverse to the flow and antivibration bars have been used to stiffen the tubes against this motion. More recently, interest has increased in the possibility of FEI occurring in the streamwise direction, parallel to the flow. This is the subject of the present paper. Numerical simulations have been carried out to study the effects of tube-to-support clearance, tube sliding friction, tube-to-support preload, and ambient turbulence levels on the FEI threshold in the streamwise direction. As one would expect, increasing friction and tube preload against the support both tend to stabilize the tube against streamwise FEI. Importantly, the results also show that decreasing tube-support clearances destabilizes streamwise FEI while having little effect on transverse FEI. Increasing ambient turbulence levels also has the effect of destabilizing streamwise FEI.

Flow-Induced Vibration of Tube Arrays With Various Pitch-to-Diameter Ratios

1982 ◽  
Vol 104 (3) ◽  
pp. 168-174 ◽  
Author(s):  
H. Tanaka ◽  
S. Takahara ◽  
K. Ohta
Keyword(s):  
Fluid Dynamic ◽  
Cross Flow ◽  
Diameter Ratio ◽  
Flow Induced Vibration ◽  
Threshold Velocity ◽  
Unsteady Forces ◽  
Practical Applications ◽  
Tube Arrays ◽  
Dynamic Forces ◽  
Unsteady Fluid

Tube arrays in cross flow start to vibrate abruptly when the flow reaches at a certain velocity. The threshold flow velocity depends upon the geometrical arrangement of tubes. It is very important for practical applications to understand the relations between the threshold velocity and pitch-to-diameter ratio of tube array. Unsteady fluid dynamic forces on a tube array with a pitch-to-diameter ratio of 2.0 were clarified experimentally and the characteristics of the threshold velocity were revealed by calculating the velocity with the unsteady forces. By comparing the threshold velocities of tube arrays of pitch-to-diameter ratio of 2.0 and 1.33, the characteristics of threshold velocity with respect to pitch-to-diameter ratio were clarified.

Two-Phase Flow-Induced Vibration of Parallel Triangular Tube Arrays With Asymmetric Support Stiffness

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Paul Feenstra ◽  
David S. Weaver ◽  
Tomomichi Nakamura
Keyword(s):  
Two Phase Flow ◽  
Cross Flow ◽  
Phase Flow ◽  
Heat Exchanger Tube ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Tube Arrays ◽  
Tube Bundles ◽  
Pitch Ratio ◽  
Exchanger Tube

Laboratory experiments were conducted to determine the flow-induced vibration response and fluidelastic instability threshold of model heat exchanger tube bundles subjected to a cross-flow of refrigerant 11. Tube bundles were specially built with tubes cantilever-mounted on rectangular brass support bars so that the stiffness in the streamwise direction was about double that in the transverse direction. This was designed to simulate the tube dynamics in the U-bend region of a recirculating-type nuclear steam generator. Three model tube bundles were studied, one with a pitch ratio of 1.49 and two with a smaller pitch ratio of 1.33. The primary intent of the research was to improve our understanding of the flow-induced vibrations of heat exchanger tube arrays subjected to two-phase cross-flow. Of particular concern was to compare the effect of the asymmetric stiffness on the fluidelastic stability threshold with that of axisymmetric stiffness arrays tested most prominently in literature. The experimental results are analyzed and compared with existing data from literature using various definitions of two-phase fluid parameters. The fluidelastic stability thresholds of the present study agree well with results from previous studies for single-phase flow. In two-phase flow, the comparison of the stability data depends on the definition of two-phase flow velocity.

scholarly journals Vibrations of Slender Structures Caused by Vortices

2021 ◽  
Vol 1203 (2) ◽  
pp. 022025
Author(s):  
Irena Gołębiowska ◽  
Maciej Dutkiewicz ◽  
Tomasz Lamparski ◽  
Poorya Hajyalikhani
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Transmission Lines ◽  
Flow Direction ◽  
Vortex Wake ◽  
Small Aspect Ratio ◽  
Flow Induced Vibration ◽  
Cylindrical Structures ◽  
Overhead Transmission Lines ◽  
Elastically Supported

Abstract Slender cylindrical structures such as overhead transmission lines, skyscrapers, chimneys, risers, and pipelines can experience flow induced vibration (FIV). The vortex vibrations are a type of FIV; they arise because of oscillating forces caused by flow separation and the detachment of vortices. The paper presents a brief overview of experimental research on vortex induced vibration - VIV of short, rigid cylinders elastically supported (with a small aspect ratio). This overview summarizes the basic results of the vortex vibration (VIV) which have been performed in the last five decades. These studies were mainly related to determining the influence of selected parameters - mass, damping and Reynolds number on the cylinder response, either in one direction only or simultaneously in the flow direction and transverse to the flow direction, and with the search for a map of vortex images in the trace (vortex wake pattern map).

The Effect of Flat Bar Supports on Streamwise Fluidelastic Instability in Heat Exchanger Tube Arrays

2014 ◽  
Author(s):  
Marwan Hassan ◽  
David S. Weaver
Keyword(s):  
Sliding Friction ◽  
Streamwise Direction ◽  
Flow Induced Vibration ◽  
Direction Parallel ◽  
Short Period ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Excitation Mechanisms ◽  
The Subject ◽  
Ambient Turbulence

Flow-induced vibration is an important criterion for the design of heat exchangers in nuclear, fossil and chemical plant. Of the several known vibration excitation mechanisms, fluidelastic instability (FEI) is the most serious because it can cause tube failures in a relatively short period of time. Traditionally, FEI has been observed to occur in the direction transverse to the flow and anti-vibration bars (AVB) have been used to stiffen the tubes against this motion. More recently, interest has increased in the possibility of FEI occurring in the streamwise direction, parallel to the flow. This is the subject of the present paper. Numerical simulations have been carried out to study the effects of tube-to-support clearance, tube sliding friction, tube-to-support preload, and ambient turbulence levels on the FEI threshold in the streamwise direction. As one would expect, increasing friction and tube preload against the support both tend to stabilize the tube against streamwise FEI. Importantly, the results also show that decreasing tube-support clearances destabilizes streamwise FEI while having little effect on transverse FEI. Increasing ambient turbulence levels also has the effect of destabilizing streamwise FEI.

Flow-induced vibration control of a circular cylinder using rotational oscillation feedback

2018 ◽  
Vol 847 ◽  
pp. 93-118 ◽  
Author(s):  
D. Vicente-Ludlam ◽  
A. Barrero-Gil ◽  
A. Velazquez
Keyword(s):  
Circular Cylinder ◽  
Transverse Velocity ◽  
Water Channel ◽  
Transverse Displacement ◽  
Flow Induced Vibration ◽  
Rotational Oscillation ◽  
Image Velocimetry ◽  
Steady State Oscillation ◽  
Type Response

The effect of imposed rotation on a slender elastically mounted circular cylinder free to oscillate transversely to the incident flow has been studied experimentally in a free-surface water channel. Rotation rate and direction are imposed to be proportional to either the cylinder’s transverse displacement or the cylinder’s transverse velocity to determine the effectiveness of these rotation laws to control the dynamics of the cylinder, either to reduce or to enhance oscillations. The former can be of interest for energy harvesting purposes whereas the latter can be useful to avoid unwanted oscillations. In all cases, non-dimensional mass and damping are fixed ($m^{\ast }=11.7$, $\unicode[STIX]{x1D701}=0.0043$) so the analysis is focused on the role of the rotation law and the reduced velocity. The Reynolds number based on the diameter of the cylinder ranges from 1500 to 10 000. Results are presented in terms of steady-state oscillation characterization (say, amplitude and frequency) and wake-pattern topology, which was obtained through digital particle image velocimetry. Both laws are able to either reduce or enhance oscillations, but they do it in a different way. A rotation law proportional to the cylinder’s displacement is more effective to enhance oscillations. For high enough actuation, a galloping-type response has been found, with a persistent growth of the amplitude of oscillations with the reduced velocity that shows a new desynchronized mode of vortex shedding. On the other hand, a rotation law proportional to the cylinder’s transverse velocity is more efficient to reduce oscillations. In this case only vortex-induced-type responses have been found. A quasi-steady theoretical model has been developed, which helps to explain why a galloping-type response may appear when rotation is proportional to cylinder displacement and is able to predict reasonably the amplitude of oscillations in those cases. The model also explains why a galloping-type response is not expected to occur when rotation is proportional to the cylinder’s velocity.

Analysis of Fluid-Induced Excitation Forces in Triangular Tube Arrays Based on the LES Method

2013 ◽  
Author(s):  
Qing-lei Jiang ◽  
Ji-yun Zhou ◽  
Xian-yuan Wang
Keyword(s):  
Numerical Models ◽  
Random Excitation ◽  
Periodic Excitation ◽  
Frequency Range ◽  
Steam Generators ◽  
Flow Induced Vibration ◽  
Small Pitch ◽  
Tube Arrays ◽  
Lift Forces ◽  
Transition Procedure

The turbulence-induced excitation and periodic wake shedding are two important flow-induced vibration mechanisms of tube arrays in steam generators and were normally considered to be random excitation and periodic excitation respectively. Recent findings show that the turbulence-induced excitation is actually the quasi-periodic excitation, which is similar to periodic excitation. Since the turbulence-induced excitation generally occurs in the small pitch-diameter ratio (P/D ratio) tube arrays and the periodic excitation occurs only at large pitch-diameter ratios, the turbulence-induced excitation mechanism seems essentially another form of the periodic excitation at small P/D ratios. To verify this hypothesize and figure out the transition procedure from periodic excitation to quasi-periodic excitation, Numerical simulations were conducted on triangle tube arrays with P/D ratios of 1.47 to 4.0 based on the LES method. Numerical results were compared with experiments results to verify the reliability of numerical models. The lift forces and the force spectra at indifferent P/D ratios were obtained to study the evolution mechanism between turbulence-induced excitation and periodic excitation. The results show that the turbulence-induced excitation and quasi-periodic excitation in tube arrays are essentially other forms of the periodic excitation. The lift forces changed from periodic excitation to quasi-periodic excitation when the P/D ratio was between 2.5 and 3.0, and the lift force nearly complete random excitation when P/D ratios below 1.5. The frequency range of the random excitation is 0 to 50Hz. The peak frequencies of the quasi-periodic excitation were greater than that of periodic excitation and decreased with the increase of P/D ratios.

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