Numerical Simulation of Flow-Induced Vibration of a Rectangular Cylinder

2003 ◽  
Author(s):  
Atsushi Enya ◽  
Atsushi Okajima
Keyword(s):  
Bluff Body ◽  
Cross Flow ◽  
Uniform Flow ◽  
Low Velocity ◽  
Flow Induced Vibration ◽  
Eddy Simulation ◽  
Rectangular Cylinder ◽  
Flow Induced Vibrations ◽  
High Reynolds ◽  
Elastically Supported

It is important for industrial purposes to predict flow-induced vibration of a bluff body elastically supported in an uniform flow. In this paper, the free oscillation of a rectangular cylinder with two-degree of freedom in the streamwise (in-line) and cross-flow (transverse) directions in a uniform flow, was computed by the Large Eddy Simulation (LES) method at high Reynolds number of 2.2 × 104. The Smagorinsky model was used as a subgrid scale (SGS) model. The main objectives of this work were to predict and estimate characteristics of flows around a free-oscillating cylinder. The present computations successfully reproduce various types of flow-induced vibrations of a free-oscillating rectangular cylinder as found by experiments; in-line oscillation, eddy-excitation and low-velocity galloping.

Flow-Induced Vibrations of a Rotated Square Tube Array Subjected to Single-Phase Cross-Flow

2021 ◽  
Author(s):  
Sameh Darwish ◽  
Abdallah Hadji ◽  
Huy-Peter Pham ◽  
Njuki W. Mureithi ◽  
Minki Cho
Keyword(s):  
Transverse Direction ◽  
Cross Flow ◽  
Experimental Tests ◽  
Low Velocity ◽  
Flow Induced Vibration ◽  
Paper Test ◽  
Array Configuration ◽  
Flexible Tube ◽  
Spacing Ratio ◽  
Flow Induced Vibrations

Abstract This paper investigates the flow-induced vibration (FIV) and possibility of fluidelastic instability occurrence in a rotated square geometry tube array through a series of experimental tests. All experiments presented here were conducted in water cross-flow. The array pitch spacing ratio of approximately P/D=1.64 is somewhat larger than that commonly found in typical steam generators. The stability of a single flexible tube as well as multiple flexible tubes were investigated. The tubes were free to vibrate purely in the streamwise direction or the transverse direction relative to the upstream flow. A single flexible tube, in the otherwise rigid tube array, was found to undergo large amplitude vibrations (up to 40 % D) in the transverse direction. Tube vibration frequency analysis indicated the presence of two frequency components related to vorticity shedding in the array. This potential vorticity-induced-vibrations (VIV) and potential coupling between VIV and FEI are discussed in the paper. Test results for streamwise flow-induced vibrations are also presented. Results in water flow show a possible effect related to flow periodicity at low velocity. At significantly high flow velocities, the tubes are found to fully restabilize. This restabilization after VIV locking has not been previously reported as an unlocking result. The present results suggest that the flow-induced vibration of tubes in a rotated square array configuration is significantly more complex than in other geometries, particularly for the streamwise vibration case.

Experimental Study on Flow-Induced Vibration of Floating Squared Section Cylinders With Low Aspect Ratio: Part II — Effects of Rounded Edges

2016 ◽  
Author(s):  
Rodolfo T. Gonçalves ◽  
Dennis M. Gambarine ◽  
Aline M. Momenti ◽  
Felipe P. Figueiredo ◽  
André L. C. Fujarra
Keyword(s):  
Aspect Ratio ◽  
Reynolds Numbers ◽  
Ocean Basin ◽  
Separation Point ◽  
Flow Induced Vibration ◽  
Low Aspect Ratio ◽  
Aspect Ratios ◽  
Significant Difference ◽  
Flow Induced Vibrations ◽  
Elastically Supported

Experiments regarding flow-induced vibration on floating rounded squared section cylinders with low aspect ratio were carried out in an ocean basin equipped with a rotating-arm apparatus. Floating squared section cylinders with rounded edges and aspect ratios of L/D = 2.0 were elastically supported by a set of linear springs in order to provide low structural damping to the system. Two different incidence angles were tested, namely 0 and 45 degrees. The Reynolds numbers covered the range from 2,000 to 30,000. The aim was to understand the flow-induced vibrations around single columns, gathering information for further understanding the causes for the Vortex-Induced Motions in semi-submersible and TLP platforms. Experiments on circular and squared sections cylinders (without rounded edges) were also carried out to compare the results with the rounded square section cylinders (with rounded edges). The amplitude results for in-line, transverse and yaw amplitude for 0-degree models showed to be higher for squared section cylinders compared to those for the rounded square section cylinders. No significant difference between the 45-degree models was observed. The results of ratio between frequency of motion in the transverse direction and natural frequency in still water confirmed the vortex-induced vibration behavior for the squared and rounded square section cylinders for 45-degree incidence; and also the galloping characteristics for 0-degree incidence cases. The rounded effect on the square section cylinders showed to be important only for reduced velocity larger than 8, which is probably related to the position of the separation point that changes around the rounded edge, behavior that did not occurr for the squared edge that fixed the separation point for any reduced velocity.

Risks for Flow Induced Vibrations (FIV) at EPU

2008 ◽  
Author(s):  
Per Nilsson ◽  
Eric Lillberg
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Cross Flow ◽  
Flow Induced Vibration ◽  
Resonance Vibrations ◽  
Flow Induced Vibrations ◽  
Risk Areas ◽  
Tube Banks ◽  
Semi Empirical ◽  
Simple Search

This work deals with risk areas for flow induced vibration at extended power uprate, EPU. The focus is on the mechanisms of excitation in one phase relevant for Swedish BWRs and PWRs. FIV-events that have occurred in nuclear power plants over the world have been collected and categorized. The most relevant events for EPU are summarized to: vibrations in steam systems due to turbulence or vortex shedding and resonance, vibrations of internal parts and also thermal mixers and sleeves or in valves and vibrations of tube banks in partial or full cross flow. Based on the collected events and some semi-empirical methods, a simple search list for FIV by power uprate has been developed. In principle these changes lead to increased risks: changed flow velocity, decreased water temperature and increased steam temperature and decreased structural damping, mass or stiffness. In addition to that, the typical collected events should be regarded.

The Nature of Self-Excitation in the Flow-Induced Vibration of Flat Plates

1964 ◽  
Vol 86 (3) ◽  
pp. 599-606 ◽  
Author(s):  
P. S. Eagleson ◽  
G. K. Noutsopoulos ◽  
J. W. Daily
Keyword(s):  
Bluff Body ◽  
Body Motion ◽  
Vibrational Amplitude ◽  
Flat Plates ◽  
Flow Induced Vibration ◽  
Trailing Edges ◽  
Flow Induced Vibrations ◽  
Plate Spring ◽  
Spring System ◽  
Bluff Body Wake

Flow-induced vibrations of flat plates are studied in water. An equation of motion of the plate-spring system is formulated incorporating the hydrodynamic loads given by the linearized potential theory, and the unknown, vortex-induced, forcing moments. Considerations of bluff-body wake dynamics show the coefficient of this forcing moment to be a function of the steady-body Strouhal number, the chord-to-thickness ratio, and a self-excitation parameter which contains the transverse body motion. This function is evaluated for plates with different trailing edges using experimental measurements of vibrational amplitude and frequency, and the nature of its dependence on vibration is shown to be equivalent to a negative damping. The poles of the amplitude-response relation are shown to predict the bounds of the zone in which large vibrational (“singing”) motion occurs. Criteria are offered for the design of systems to avoid these self-excited vibrations.

Modeling of Flow-Induced Vibrations in Heat Exchangers and Nuclear Reactors

1974 ◽  
Vol 96 (4) ◽  
pp. 358-364 ◽  
Author(s):  
G. S. Beavers ◽  
R. Plunkett
Keyword(s):  
Reynolds Number ◽  
Heat Exchangers ◽  
Single Phase ◽  
Nuclear Reactors ◽  
Cross Flow ◽  
Flow Region ◽  
Light Water ◽  
Excited Vibration ◽  
Flow Induced Vibrations ◽  
High Reynolds

This paper discusses the appropriate scaling factors for the modeling of the fluid-mechanical interaction of complex structures. The possible mechanisms of flow-excited vibration are described, and scaling parameters are derived from considerations of the mechanical and fluid systems. The paper is particularly concerned with the flow-induced vibrations of banks of cylinders in single phase, high Reynolds number, turbulent, cross flow, as occur for example in light water nuclear reactors and heat exchangers. It is concluded that the modeling of the tube banks in light water nuclear reactors will involve a mismatch of Reynolds number, but that the major phenomena of fluid-solid interaction in the single-phase flow region will probably be closely replicated if the Reynolds number is high enough so that the entering flow is turbulent and if the scaling ratio is not too large.

Numerical Investigation on Lock-In Condition and Convective Heat Transfer From an Elastically Supported Cylinder in a Cross Flow

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
F. Baratchi ◽  
M. Saghafian ◽  
B. Baratchi
Keyword(s):  
Nusselt Number ◽  
Natural Frequencies ◽  
Numerical Study ◽  
Cross Flow ◽  
Elastic Cylinder ◽  
Overset Grids ◽  
Wide Range ◽  
Flow Induced Vibrations ◽  
Lock In ◽  
Elastically Supported

In this numerical study, flow-induced vibrations of a heated elastically supported cylinder in a laminar flow with Re = 200 and Pr = 0.7 are simulated using the moving overset grids method. This work is carried out for a wide range of natural frequencies of the cylinder, while for all cases mass ratio and reduced damping coefficient, respectively, are set to 1 and 0.01. Here we study lock-in condition and its effects on force coefficients, the amplitude of oscillations, vortex shedding pattern, and Nusselt number and simultaneously investigate the effect of in-line oscillations of the cylinder on these parameters. Results show that for this cylinder, soft lock-in occurs for a range of natural frequencies and parameters like Nusselt number, and the amplitude of oscillation reach their maximum values in this range. In addition, this study shows that in-line oscillations of the cylinder have an important effect on its dynamic and thermal behavior, and one-degree-of-freedom simulation, for an elastic cylinder, which can vibrate freely in a flow field, is only valid for cases far from soft lock-in range.

scholarly journals Experimental studies of a single flexibly-mounted rod in a triangular rod bundle in cross-flow

2018 ◽  
Vol 148 ◽  
pp. 09002
Author(s):  
Sabine Upnere ◽  
Normunds Jekabsons ◽  
Sergejs Dementjevs ◽  
Michael Wohlmuther
Keyword(s):  
Experimental Studies ◽  
Cross Flow ◽  
Flow Induced Vibration ◽  
Rod Bundle ◽  
Rod System ◽  
Flow Induced Vibrations ◽  
The Stability ◽  
Paul Scherrer ◽  
Fixed Array ◽  
Rod Array

Experiments on flow-induced vibrations using a closely-packed triangular rod array with a pitch-todiameter ratio of 1.1 in water cross-flow was carried out at Paul Scherrer Institute. The bundle consists of 21 row of five rods in each one. Single flexibly-mounted test rod (TR) is in the fourth row in an otherwise fixed array. The test rod can freely move in the transverse and in-line direction. Two accelerometer sensors were attached at both ends of the TR to measure the rod response on the fluid flow. The effect of flow rate on the stability of the flexibly-mounted TR has been analysed. During experiments, it reveals a set of conditions and tendencies for the flow-induced vibration in the closely-packed multi-rod system.

Large-Eddy Simulation of Cross-Flow Induced Vibrations of a Single Flexible Tube in a Normal Square Tube Array

2014 ◽  
Author(s):  
Julien Berland ◽  
Enrico Deri ◽  
André Adobes
Keyword(s):  
Cross Flow ◽  
Operating Conditions ◽  
Flexible Tube ◽  
Eddy Simulation ◽  
Drag Forces ◽  
Large Eddy ◽  
Flow Induced Vibrations ◽  
Lift And Drag ◽  
Envelope Spectrum ◽  
Mass Spring

The cross-flow induced vibrations in water of a single flexible tube in a normal square array of rigid tubes are investigated by means of large-eddy simulations, based on the classical Smagorinsky model. The flow configuration and the operating conditions are taken from the experiments of Granger et al. (J. Fluid Struct., 1993). A fully-coupled fluid-structure calculation is hence performed: the tube dynamics is modeled by a mass-spring-damper system, and the motion of the fluid domain is accounted for by a moving mesh technique. The numerical results are compared to the experimental data in terms of amplitude and frequency of the flexible tube oscillations, for various inflow velocities. In addition, characteristics of the flow-induced forces are discussed: features of the power spectral densities of lift and drag forces, such as the envelope spectrum or the spanwise correlation length are investigated.

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