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.

Flow-Induced Vibration Behaviour of a Rotated Square Tube Array Subjected to Cross-Flow

2021 ◽  
Author(s):  
S. Darwish ◽  
A. Hadji ◽  
H. P. Pham ◽  
N. Mureithi ◽  
C. H. Ha
Keyword(s):  
Water Flow ◽  
Transverse Direction ◽  
Cross Flow ◽  
Experimental Tests ◽  
Low Velocity ◽  
Flow Induced Vibration ◽  
Paper Test ◽  
Array Configuration ◽  
Flexible Tube ◽  
Spacing Ratio

Abstract The present paper presents experimental tests investigating flow-induced vibration and possible fluidelastic instability (FEI) in a rotated square geometry tube array. The pitch spacing ratio of approximately P/D = 1.64 is somewhat larger than that found in typical array geometries. Experiments were conducted in water flow. The stability of a single flexible tube as well as multiple flexible tubes was 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 response PSDs 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 is discussed in the paper. Test results for streamwise flow-induced vibrations are also presented. Results in water flow show a possible effect related to VIV at low velocity. At significantly high flow velocity, 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 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.

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.

Two-Phase Flow Induced Vibration of an Array of Tubes Preferentially Flexible in the Flow Direction

2005 ◽  
Author(s):  
R. Violette ◽  
N. W. Mureithi ◽  
M. J. Pettigrew
Keyword(s):  
Natural Frequencies ◽  
Flow Direction ◽  
Cross Flow ◽  
Diameter Ratio ◽  
Phase Flow ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Array Configuration ◽  
Fluidelastic Instability ◽  
Existing Data

Tests were done to study the fluidelastic instability of a cluster of seven cylinders much more flexible in the flow direction than in the lift direction. The array configuration is rotated triangular with a pitch to diameter ratio of 1.5. The array was subjected to two-phase (air-water) cross flow. Cylinder natural frequencies of 14 and 28 Hz were tested. Fluidelastic instabilities were observed at 65, 80, 90 and 95% void fraction albeit at a somewhat higher flow velocity than that expected for axisymetrically flexible arrays. These results and additional wind tunnel results are compared to existing data on fluidelastic instability.

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.

Research on Cross Flow Induced Vibration of Flexible Tube Bundle

2017 ◽  
Author(s):  
Zhipeng Feng ◽  
Wenzheng Zhang ◽  
Yixiong Zhang ◽  
Fenggang Zang ◽  
Huanhuan Qi ◽  
...  
Keyword(s):  
Critical Velocity ◽  
Dynamic Equilibrium ◽  
Tube Bundle ◽  
Lift Coefficient ◽  
Three Dimensional ◽  
Cross Flow ◽  
Nonlinear Phenomena ◽  
Flow Induced Vibration ◽  
Navier Stokes Equation ◽  
Flexible Tube

When the elastic deformation of the tube bundle is considered, the interaction between the flow field and the structure becomes more complicated. In order to investigate the flow induced vibration (FIV) problems in flexible tube bundle, a numerical model for fluid-structure interaction system was presented firstly. The unsteady three-dimensional Navier-Stokes equation and LES turbulence model were solved with the finite volume approach on structured grids combined with the technique of dynamic mesh. The dynamic equilibrium equation was discretized according to the finite element theory. The configurations considered are tubes in a cross flow. Firstly, the flow-induced vibration of a single flexible tube under uniform turbulent flow are calculated when Reynolds number is 1.35× 104. The variety trends of lift, drag, displacement, vertex shedding frequency, phase difference of tube are analyzed under different frequency ratios. The nonlinear phenomena of locked-in, phase-switch are captured successfully. Meanwhile, the limit cycle and bifurcation of lift coefficient and displacement are analyzed using trajectory, phase portrait and Poincare sections. Secondly, the mutual interaction of two in-line flexible tubes is investigated. Different behaviors, bounded by critical distances between the tubes, critical velocity, and wake vortex pattern are highlighted. Finally, four tube bundle models were established to study the effect of the number of flexible tube on the FIV characteristics. Thanks to several calculations, the critical velocity of instability vibration and the effect of tube bundle configurations on fluid forces and dynamics were obtained successfully. It is therefore expected that further calculations, with model refinements and other validation studies, will bring valuable informations about bundle stability. Further comparisons with experiment are necessary to validate the behavior of the method in this configuration.

Flow-Induced Vibration of a Cylinder in the Wake of Another of Smaller Diameter

2014 ◽  
Author(s):  
Md. Mahbub Alam ◽  
An Ran ◽  
Yu Zhou
Keyword(s):  
Circular Cylinder ◽  
Free Stream ◽  
Cross Flow ◽  
Induced Response ◽  
Stream Velocity ◽  
Flow Induced Vibration ◽  
Cylinder Diameter ◽  
Spacing Ratio ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency

This paper presents cross-flow induced response of a both-end-spring-mounted circular cylinder (diameter D) placed in the wake of a rigid circular cylinder of smaller diameter d. The cylinder vibration is constrained to the transverse direction. The cylinder diameter ratio d/D and spacing ratio L/d are varied from 0.2 to 1.0 and 1.0 to 5.5, respectively, where L is the distance between the center of the upstream cylinder to the forward stagnation point of the downstream cylinder. A violent vibration of the cylinder is observed for d/D = 0.2 ∼ 0.8 at L/d = 1.0, for d/D = 0.24 ∼ 0.6 at 1.0 < L/d ≤ 2.5, for d/D = 0.2 ∼ 0.4 at 2.5 < L/d ≤ 3.5, and for d/D = 0.2 at 3.5 < L/d ≤ 5.5, but not for d/D = 1.0. A smaller d/D generates vibration for a longer range of L/d. The violent vibration occurs at a reduced velocity Ur (=U∞/fnD, where U∞ is the free-stream velocity and fn the natural frequency of the cylinder system) beyond the vortex excitation regime (Ur ≥ 8) depending on d/D and L/d. Once the vibration starts to occur, the vibration amplitude increases rapidly with increasing Ur. It is further noted that the flow behind the downstream cylinder is characterized by two predominant frequencies, corresponding to the cylinder vibration frequency and the natural vortex shedding frequency of the cylinder, respectively. While the former persists downstream, the latter vanishes rapidly.

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.

Characteristics of Aerodynamic Sound Radiated From Two Finned Cylinders

2014 ◽  
Author(s):  
Hiromitsu Hamakawa ◽  
Hiroki Matsuoka ◽  
Kazuki Hosokai ◽  
Eiichi Nishida ◽  
Eru Kurihara
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Transverse Direction ◽  
Flow Direction ◽  
Cross Flow ◽  
Near Wake ◽  
Aerodynamic Sound ◽  
Spacing Ratio ◽  
Staggered Arrangement ◽  
Karman Vortex

In the present paper the attention is focused on the characteristics of aerodynamic sound radiated from two finned cylinders with tandem and staggered arrangement exposed to cross-flow. We measured the spectrum of SPL and flow velocity for the cylinder spacing ratios ranged from 0 to 1.05 in the transverse direction and the ratios from 1.24 to 6.8 in the flow direction at Reynolds number of 1.0×105−1.9×105. As a result, we found that the peak SPL and Strouhal number of vortex shedding for two finned cylinders depend on the cylinder spacing ratios as well as those for bare cylinders. The peak SPL of the spectrum varied complexly with the tube spacing ratio. The peak levels of SPL for tandem finned cylinders were approximately 8 dB lower than that for the tandem bare cylinders. At the cylinder spacing ratio of 1.24 in the flow direction, the peak SPL for two finned cylinders at the cylinder spacing ratio of 0.72 in the transverse direction was about 8 dB larger than that for tandem finned cylinders. The peak SPL depended on the spanwise correlation length of the Karman vortex formed in the near wake of the downstream of two finned cylinders.

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.

Experimentally-Tuned Finite Element Model of Flow-Induced Vibrations in a Square Tube Bundle Subjected to Cross-Flow

2012 ◽  
Author(s):  
Y. A. Khulief ◽  
S. A. Said
Keyword(s):  
Finite Element ◽  
Dynamic Model ◽  
Complex Dynamics ◽  
Tube Bundle ◽  
Cross Flow ◽  
Element Model ◽  
Analytical Models ◽  
Test Rig ◽  
Flow Induced Vibration ◽  
Flow Induced Vibrations

It has been recognized that modeling of the complex dynamics of fluidelastic forces, that give rise to vibrations of tube bundles, requires a comprehensive dynamic model of high fidelity based on experimental insight. Accordingly, the prediction of the flow-induced vibration due to unsteady cross-flow can be greatly aided by semi-analytical models, in which some coefficients are determined experimentally. In this paper, the elastodynamic model of the tube array is formulated using the finite element approach, wherein each tube is modeled by a set of finite tube-elements. The interaction between tubes in the bundle is represented by fluidelastic coupling forces, which are defined in terms of the multi-degree-of-freedom elastodynamic behavior of each tube in the bundle. A laboratory test rig with an instrumented square bundle is constructed to measure the fluidelastic coefficients used to tune the developed dynamic model. The test rig admits two different test bundles; namely the inline-square and 45° rotated-square tube arrays. Measurements were conducted to identify the flow-induced dynamic coefficients. The developed scheme was utilized in predicting the onset of flow-induced vibrations, and results were examined in the light of TEMA predictions. The comparison demonstrated that TEMA guidelines are more conservative in the two configurations considered.

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