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.

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.

Two-Phase Flow-Induced Vibration: An Overview (Survey Paper)

1994 ◽  
Vol 116 (3) ◽  
pp. 233-253 ◽  
Author(s):  
M. J. Pettigrew ◽  
C. E. Taylor
Keyword(s):  
Two Phase Flow ◽  
Cross Flow ◽  
Axial Flow ◽  
Random Excitation ◽  
Phase Flow ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Vibration Excitation ◽  
Fluidelastic Instability ◽  
Excitation Mechanisms

Two-phase flow exists in many industrial components. To avoid costly vibration problems, sound technology in the area of two-phase flow-induced vibration is required. This paper is an overview of the principal mechanisms governing vibration in two-phase flow. Dynamic parameters such as hydrodynamic mass and damping are discussed. Vibration excitation mechanisms in axial flow are outlined. These include fluidelastic instability, phase-change noise, and random excitation. Vibration excitation mechanisms in cross-flow, such as fluidelastic instability, periodic wake shedding, and random excitation, are reviewed.

Flow-Induced Vibration in Spiral Finned Gas Tube Bundle Heat Exchangers

2003 ◽  
Author(s):  
Michael Fischer
Keyword(s):  
Heat Exchangers ◽  
Tube Bundle ◽  
Practical Importance ◽  
Acoustic Resonance ◽  
Finned Tube ◽  
Flow Induced Vibration ◽  
Finned Tubes ◽  
The Past ◽  
Short Period ◽  
Fluidelastic Instability

In the past finned tube bundle heat exchangers were often subject of severe damages due to flow-induced vibration followed by high amounts of loss for the operator. A case of practical importance is the design of spiral finned gas tube bundle heat exchangers that still have been investigated in literature only seldom. Both acoustic resonance and fluidelastic instability can lead to tube rupture within a short period of operation. In this paper analytic calculation methods for tube Eigenfrequencies are extended to spiral finned tubes. The results are in agreement with static and vibrational experiments. Stability criteria for fluidelastic instability are derived by flow channel experiments extending Connor’s equation to the design of spiral finned tube bundles. A number of cases of damage is described. The importance of correct damping values is demonstrated. The scheme reported in this paper is able to avoid damages in spiral finned tube bundle heat exchangers due to fluidelastic instability.

Fluidelastic Instability of a Single Flexible Tube in a Rigid Tube Array

2010 ◽  
Author(s):  
Ahmed Khalifa ◽  
David Weaver ◽  
Samir Ziada
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Precise Control ◽  
Flexible Tube ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Excitation Mechanisms ◽  
The Stability ◽  
Square Array ◽  
Special Case

Tube and shell heat exchangers are commonly used in both fossil and nuclear power plants. The unexpected failure for such components is expensive and potentially dangerous. Of the various excitation mechanisms which can cause excessive tube vibration, fluidelastic instability is the most dangerous and therefore has received the most attention. The present study reviews the experimental work published in the open literature which involves the use of a single flexible tube in a rigid array to study fluidelastic instability. The data are categorized based on the array geometry into four main groups, parallel triangular, normal triangular, rotated square, and square array patterns. It is concluded from this review that the simplification of using a single flexible tube in a rigid array to study fluidelastic instability should be done with great care, and precise control of some parameters is essential to obtain reliable and repeatable results. Fluidelastic instability of a single flexible tube in a rigid array may occur in some cases, and may be used to improve our understanding of the phenomenon. However, it must be noted that this behavior is a special case and not generally useful for determining the stability of tube arrays.

Implementation in VIBIC of an Improved Time-Domain Simulation Model for Fluidelastic Instability in Tube Arrays

2014 ◽  
Author(s):  
Teguewinde Sawadogo ◽  
Yingke Han ◽  
Njuki Mureithi
Keyword(s):  
Time Domain ◽  
Continuous Extension ◽  
Computer Code ◽  
Force Model ◽  
Time Domain Simulation ◽  
Runge Kutta Method ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Excitation Mechanisms ◽  
Delay Differential

VIBIC (Vibration of Beams with Intermittent Contacts) is a non-linear dynamics computer code developed and maintained by Atomic Energy of Canada Limited over the past 40 years in collaboration with universities. Its main application is the assessment of possible vibration damage to steam-generator and heat exchanger tubes. This assessment is done by performing simulations of the vibration response of beam-like structures to various flow-induced excitation mechanisms, such as turbulence buffeting, vortex shedding, and fluidelastic excitation. Fluidelastic excitation is potentially the most damaging flow-induced excitation mechanism. The fluidelastic effect has, until now, been incorporated in VIBIC using the frequency-based Connors model. To properly perform a time-domain simulation of fluidelastic-induced vibration, a time-domain fluidelastic force model is needed. In the present work, a time-domain formulation of the fluidelastic forces based on the quasi-steady model is implemented in VIBIC. The time delay inherent to the quasi-steady model is taken into account by using a delayed displacement in the expression of the fluidelastic forces. The resulting modal equations are delay differential equations that are solved using a continuous extension of the Runge-Kutta method. Both linear and nonlinear fluid force models are incorporated. The fluidelastic instability results predicted by the models are compared to known theoretical and experimental results for validation. The predictions of the models are in good agreement with those results. The results given by the nonlinear quasi-steady fluidelastic forces are found to be more realistic than those of the linear quasi-steady fluidelastic forces. A realistic simulation of the post-instability behaviour is made possible through the use of the nonlinear fluidelastic forces.

Pitch and Pattern Effects on Streamwise Fluidelastic Instability in Tube Arrays

2019 ◽  
Author(s):  
Marwan Hassan ◽  
David Weaver
Keyword(s):  
Los Angeles ◽  
Channel Model ◽  
High Mass ◽  
Flow Induced Vibration ◽  
Geometric Patterns ◽  
Small Pitch ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Pitch Ratio ◽  
The Stability

Abstract Fluidelastic instability (FEI) is well known to be a critical flow-induced vibration concern for the integrity of the tubes in nuclear steam generators. Traditionally, this has been assumed to occur in the direction transverse to the direction of flow but the tube failures at San Onofre Nuclear Generating Station (SONGS) in Los Angeles proved that this assumption is not generally valid. A simple tube-in-channel theoretical model was previously developed to predict streamwise as well as transverse FEI in a parallel triangular tube array. This predicted that this array geometry was particularly sensitive to streamwise FEI for high mass-damping parameters and small pitch ratios, the conditions in which the SONGS failures occurred. The advantage of this simple modelling approach is that no new empirical data are required for parametric studies of the effects of tube pattern and pitch ratio on FEI. The tube-in-channel model has been extended to in-line square, normal triangular and rotated square tube arrays and the stability of these geometric patterns are analyzed for the effects of varying pitch ratio and the mass-damping parameter. The results are compared with the available experimental data and conclusions are drawn regarding the relative vulnerability of these different tube array geometries to streamwise FEI.

Flow-Induced Vibrations in Power and Process Plant Components—Progress and Prospects

2000 ◽  
Vol 122 (3) ◽  
pp. 339-348 ◽  
Author(s):  
D. S. Weaver ◽  
S. Ziada ◽  
M. K. Au-Yang ◽  
S. S. Chen ◽  
M. P. Paı¨doussis ◽  
...  
Keyword(s):  
Future Research ◽  
Two Phase Flows ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Process Plant ◽  
Fluidelastic Instability ◽  
Flow Induced Vibrations ◽  
Excitation Mechanisms ◽  
Plant Components

This paper provides a brief overview of progress in our understanding of flow-induced vibration in power and process plant components. The flow excitation mechanisms considered are turbulence, vorticity shedding, fluidelastic instability, axial flows, and two-phase flows. Numerous references are provided along with suggestions for future research on unresolved issues. [S0094-9930(00)01203-8]

The Effect of Streamwise Tube Motion on the Unsteady Fluid Forces in a Normal Triangle Tube Array

2015 ◽  
Author(s):  
Salim El Bouzidi ◽  
Marwan Hassan
Keyword(s):  
Stokes Equations ◽  
Navier Stokes ◽  
Experimental Investigations ◽  
Arbitrary Lagrangian Eulerian ◽  
Streamwise Direction ◽  
Navier Stokes Equations ◽  
Critical Flow Velocity ◽  
Flow Perturbation ◽  
Short Period ◽  
Fluidelastic Instability

Fluidelastic instability is generally regarded as the most severe type of flow excitation mechanism. When this mechanism prevails, it could cause serious damage to tube arrays in a very short period of time. This mechanism is characterized by a critical flow velocity beyond which the tubes undergo unstable oscillations. Recently, a number of experimental investigations showed that it is possible to have instability in the streamwise direction; previously, it was believed that fluidelastic instability was only a concern in the direction transverse to the flow. The purpose of this study is to characterize the flow in the channels surrounding a vibrating tube in a normal triangular bundle with P/d = 1.5. The tube is oscillating in the streamwise direction with a constant amplitude. Numerical simulations were conducted by solving the unsteady Reynolds Averaged Navier-Stokes equations (uRANS) cast in Arbitrary Lagrangian-Eulerian (ALE) form. The unsteady flow perturbation is estimated along the flow channel. The pressure perturbation is used to compute the streamwise unsteady force coefficients in the context of Chen’s model. The perturbation phase and decay are extracted and utilized in the framework of the Lever & Weaver model to study the stability of tube bundles due to tube motion in the streamwise direction.

Pitch and Pattern Effects On Streamwise Fluidelastic Instability in Tube Arrays

2021 ◽  
Author(s):  
Marwan A. Hassan ◽  
David S. Weaver
Keyword(s):  
Los Angeles ◽  
Channel Model ◽  
High Mass ◽  
Flow Induced Vibration ◽  
Geometric Patterns ◽  
Small Pitch ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Pitch Ratio ◽  
The Stability

Abstract Fluidelastic instability (FEI) is well known to be a critical flow-induced vibration concern for the integrity of the tubes in nuclear steam generators. Traditionally, this has been assumed to occur in the direction transverse to the direction of flow but the tube failures at San Onofre Nuclear Generating Station (SONGS) in Los Angeles proved that this assumption is not generally valid. A simple tube-in-channel theoretical model was previously developed to predict streamwise as well as transverse FEI in a parallel triangular tube array. This predicted that this array geometry was particularly sensitive to streamwise FEI for high mass-damping parameters and small pitch ratios, the conditions in which the SONGS failures occurred. The advantage of this simple modelling approach is that no new empirical data are required for parametric studies of the effects of tube pattern and pitch ratio on FEI. The tube-in-channel model has been extended to in-line square, normal triangular and rotated square tube arrays and the stability of these geometric patterns are analyzed for the effects of varying pitch ratio and the mass-damping parameter. The results are compared with the available experimental data and conclusions are drawn regarding the relative vulnerability of these different tube array geometries to streamwise FEI.

Validation of Flow-Induced Vibration Prediction Codes: PIPO-FE and VIBIC Versus Experimental Measurements

2002 ◽  
Author(s):  
Yingke Han ◽  
Nigel J. Fisher
Keyword(s):  
Heat Exchanger ◽  
Tube Bundle ◽  
Cross Flow ◽  
Heat Exchanger Tube ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Fluidelastic Instability ◽  
Excitation Mechanisms ◽  
Vibration Damage ◽  
Exchanger Tube

The PIPO-FE and VIBIC finite-element computer codes, developed and updated over the past 30 years, are used to calculate heat exchanger tube flow-induced vibration (FIV) response. PIPO-FE includes a linear forced-vibration analysis of heat exchanger tubes subjected to all major flow-induced excitation mechanisms, namely fluidelastic instability, random turbulence-induced excitation and periodic wake shedding. VIBIC is for both linear and non-linear transient dynamic simulations of heat exchanger tubes. When used to simulate a tube with clearance supports (non-linear case), VIBIC calculates tube wear work-rates to aid in the prediction of tube fretting-wear damage. All the excitation mechanisms included in PIPO-FE analyses can be simulated in VIBIC. In addition, VIBIC can model friction forces between a tube and its supports, squeeze film forces produced by the resistance of the fluid opposing the relative motion of the tube and supports, and constant loads. An important application of these codes is the analysis of the susceptibility of a heat exchanger tube to vibration damage. These codes may be used at the design stage to assess a new heat exchanger, or during the operational stage to investigate a tube failure and determine if the damage was caused by vibration. If a vibration problem exists, then the codes can be used to assess the effectiveness of any proposed design modifications. To properly assess tube vibration damage, the codes must predict vibration response accurately. This paper documents the validation process of code predictions against measurements from three flow-induced vibration experiments conducted at Chalk River Laboratories: 1. A single-span cantilever tube bundle subjected to two-phase air-water cross flow; 2. A single-span cantilever tube bundle subjected to single- and two-phase Freon cross flow; and 3. A single-span U-bend tube bundle subjected to single-phase water and two-phase air-water partial cross flow. PIPO-FE and VIBIC code predictions for fluidelastic instability ratio and the response to random turbulence-induced excitation are compared to each other for each of these three experiments. The predictions from the two codes are in good agreement. In addition, the predictions for frequency, damping ratio, fluidelastic instability ratio and the response to random turbulence-induced excitation from both codes are in reasonable agreement with the experimental results.

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