Characteristics of Acoustic Resonance Excitation by Flow Around Inline Cylinders

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Mahmoud Shaaban ◽  
Atef Mohany
Keyword(s):  
Acoustic Pressure ◽  
Tube Bundle ◽  
Cross Flow ◽  
Acoustic Resonance ◽  
Environmental Risks ◽  
Critical Parameters ◽  
Resonance Excitation ◽  
Tube Bundles ◽  
Flow Oscillations

Excitation of acoustic resonance by flow over tube bundles in heat exchangers can cause hazardous levels of acoustic pressure that may pose operational and environmental risks. The previous studies have indicated that inline arrangements of cylinders excite acoustic resonance of a nature different from that of a single cylinder. In this work, the excitation of acoustic resonance by cross-flow around inline arrangements of cylinders is experimentally investigated to identify the role of critical parameters on resonance characteristics. Results show that flow around inline tube bundles can excite acoustic resonance due to periodic flow oscillations over the cavity formed between successive cylinders rather than periodic wake phenomena. Based on precoincidence resonance characteristics, a criterion is introduced to predict the occurrence of acoustic resonance in inline arrangements of cylinders. The proposed parametric criterion does not only identify the potential for resonance excitation for inline arrangements of cylinders experimentally investigated in this work but it also provides a method to separate resonant from nonresonant cases for inline tube bundle data from the literature.

Effect of Flow Approach Angle on Acoustic Resonance Excitation of In-Line Tube Bundles in Cross-Flow

2019 ◽  
Author(s):  
Mohammed Alziadeh ◽  
Atef Mohany ◽  
Marwan Hassan
Keyword(s):  
Tube Bundle ◽  
Flow Direction ◽  
Cross Flow ◽  
Acoustic Resonance ◽  
Resonant Mode ◽  
Acoustic Energy ◽  
Resonance Excitation ◽  
Approach Angle ◽  
Tube Bundles ◽  
Lock In

Abstract This paper presents preliminary experimental results on the influence of the flow approach angle on the acoustic resonance excitation of in-line tube bundles in cross-flow. The pitch-to-diameter ratio (P/D) of the in-line tube bundles investigated is P/D = 1.733. The flow approach angle was investigated by physically rotating the tube bundle clockwise relative to the flow direction. The tube bundles are capable of rotating with increments of 5° up to an angle of 45°. For brevity, only the results for the 0° and 30° orientation will be presented herein. For the 0° orientation, two Strouhal frequencies (St1 = 0.437 and St2 = 0.252) were observed. However, only one of these frequencies (St1 = 0.437) was capable of exciting resonance. During resonance, a peak sound pressure level (SPL) of 170 dB was achieved. The Strouhal frequencies and peak SPL agrees well with what has been presented in the literature. For the 30° orientation, only one Strouhal frequency (St1 = 0.98) was measured. At this orientation, the lock-in phenomenon occurred at a much lower flow velocity compared to the 0° orientation with a peak SPL reaching 153 dB. Jumps in the lock-in frequency were observed at the 30° orientation. This phenomenon is associated with two reasons. The first reason is a partial lock-in with an acoustic resonant mode, due to the acoustic energy not being fully trapped within the tube bundle. The second reason is related to the changes in the apparent speed of sound resulting in variations in the acoustic cross-mode frequency depending on where the excitation source is emanating from within the tube bundle. A brief summary of the results is presented in this paper.

Parametric Investigation of the Flow-Sound Interaction Mechanism for Single Cylinders in Cross-Flow

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Omar Afifi ◽  
Atef Mohany
Keyword(s):  
Heat Exchangers ◽  
Interaction Mechanism ◽  
Cross Flow ◽  
Acoustic Resonance ◽  
Industrial Applications ◽  
Resonance Excitation ◽  
Acoustic Damping ◽  
Radiation Losses ◽  
Cylinder Diameter ◽  
Tube Bundles

Abstract Flow-excited acoustic resonance is a design concern in many industrial applications. If not treated, it may lead to excessive vibrational loads, which could subsequently result in premature structural failure of critical equipment. For the case of tube bundles in heat exchangers, several acoustic damping criteria were proposed in the literature to predict the occurrence of resonance excitation. However, these criteria, in some cases, are not reliable in differentiating between the resonant and nonresonant cases. A primary reason for that is the geometrical differences between reduced scale models and full-scale tube bundles, and their effect on the flow-sound interaction mechanism. Therefore, the effect of two geometrical aspects, namely, the duct height and the cylinder diameter, on the self-excited acoustic resonance for single cylinders in cross-flow is experimentally investigated in this work. Changing the duct height changes the natural frequency of the excited acoustic modes and the duct's acoustic damping and radiation losses. Changing the cylinder diameter changes the flow velocity at frequency coincidence, the pressure drop, and Reynolds number. It is found that increasing the duct height decreases the acoustic impedance, which makes the system more susceptible to resonance excitation. This, in turn, changes the magnitude of the acoustic pressure at resonance, even for cases where the dynamic head of the flow is kept constant. The acoustic attenuation due to visco-thermal losses is quantified theoretically using Kirchhoff's acoustical damping model, which takes into account the geometrical aspects of the different ducts. Results from the experiments are compared with the acoustic damping criteria from the literature for similar cases. It is revealed that the height of the duct is an important parameter that should be included in damping criteria proposed for tube bundles of heat exchangers, as it controls the acoustic damping and radiation losses of the system, which have been over-looked in the past.

Modeling and Simulation of Cross-Flow Induced Vibration in a Multi-Span Tube Bundle

2004 ◽  
Author(s):  
Shahab Khushnood ◽  
Zaffar M. Khan ◽  
M. Afzaal Malik ◽  
Zafarullah Koreshi ◽  
Mahmood Anwar Khan
Keyword(s):  
Heat Exchanger ◽  
Tube Bundle ◽  
Cross Flow ◽  
Fatigue Cracking ◽  
Acoustic Resonance ◽  
Computer Code ◽  
Variable Geometry ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Tube Bundles

Flow-induced vibration in steam generator and heat exchanger tube bundles has been a source of major concern in nuclear and process industry. Tubes in a bundle are the most flexible components of the assembly. Flow induced vibration mechanisms, like fluid-elastic instability, vortex shedding, turbulence induced excitation and acoustic resonance results in failure due to mechanical wear, fretting and fatigue cracking. The general trend in heat exchanger design is towards larger exchangers with increased shell side velocities. Costly plant shutdowns have been the motivation for research in the area of cross-flow induced vibration in steam generators and process exchangers. The current paper focuses on the development of a computer code (FIVPAK) for the design (natural frequencies, variable geometry, tube pitch & pattern, mass damping parameter, reduced velocity, strouhal and damage numbers, added mass, wear work rates, void fraction for two-phase, turbulence and acoustic considerations etc.) of tube bundles with respect to cross flow-induced vibration. The code has been validated against Tubular Exchanger Manufacturers (TEMA), Flow-Induced Vibration code (FIV), and results on an actual variable geometry exchanger, specially manufactured to simulate real systems. The proposed code is expected to prove a useful tool in designing a tube bundle and to evaluate the performance of an existing system.

Aeroacoustic Response of a Single Cylinder With Straight Circular Fins in Cross-Flow

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Nadim Arafa ◽  
Atef Mohany
Keyword(s):  
Aspect Ratio ◽  
Acoustic Pressure ◽  
Interaction Mechanism ◽  
Cross Flow ◽  
Acoustic Resonance ◽  
Resonance Excitation ◽  
Acoustic Excitation ◽  
Pressure Amplitude ◽  
Fin Thickness ◽  
Fin Spacing

The phenomenon of sound generation has been investigated in some detail for the case of bare cylinders; however, the effect of adding fins to the cylinder on the flow–sound interaction mechanism is not yet fully understood. Thus, the aeroacoustic response of a cylinder with straight circular fins in cross-flow is investigated experimentally in this work. During the experiments, the acoustic modes of the duct housing the cylinder are self-excited due to the vortex shedding that emerges from the cylinder's surface. In order to determine the effect of different fin parameters on the onset and intensity of acoustic resonance, 14 different finned cylinders with fin thickness ranging from 0.35 to 1.5 mm and fin density ranging from 4 to 13.7 fin/in. are investigated. It is observed that the finned cylinders experience an earlier acoustic resonance and higher levels of acoustic pressure compared to their equivalent bare cylinders. Moreover, it is observed that, for constant fin spacing, the acoustic pressure amplitude increases and the acoustic resonance occurs at earlier velocities as the fin thickness increases. On the other hand, for constant fin thickness, as the fin spacing increases the amplitude of the acoustic pressure decreases while the onset of the resonance is delayed. Finally, the effect of the cylinder's aspect ratio on the acoustic resonance excitation is presented. It is shown that as the finned cylinders' aspect ratio increases from 4.85 to 11.3, the normalized acoustic pressure during resonance increases drastically. However, for bare cylinders the normalized acoustic pressure during resonance is not highly dependent on the cylinders' aspect ratio. These results indicate that adding fins to the cylinder alters the flow field downstream of the cylinder in a manner that makes it more susceptible to acoustic excitation.

Equivalent Diameter for Predicting Vortex Shedding of Finned Cylinders in Cross-Flow

2021 ◽  
Author(s):  
Mohammed Alziadeh ◽  
Atef Mohany
Keyword(s):  
Vortex Shedding ◽  
Tube Bundle ◽  
Cross Flow ◽  
Acoustic Resonance ◽  
Finned Tube ◽  
Resonance Excitation ◽  
Equivalent Diameter ◽  
Frequency Scaling ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency

Abstract This article explores different equivalent diameter equations found in the literature for shedding frequency scaling and applying it to various types of finned cylinders in industrial heat exchangers. The focus is on three finned cylinder types: straight, twist-serrated, and crimped spirally finned cylinders. Within each finned cylinder category, at least three different finned cylinders are investigated. The results indicate that utilizing the appropriate equivalent diameter for vortex shedding frequency scaling collapses the data within the Strouhal bounds of a bare cylinder away from resonance excitation. However, the onset of flow-excited acoustic resonance and peak acoustic pressure in all the finned cylinder cases occur at a reduced flow velocity earlier than their equivalent diameter bare cylinder. This suggests that although utilizing the appropriate equivalent diameter can predict the shedding frequency away from resonance, it cannot be used in velocity scaling to predict the onset of acoustic resonance in finned tube bundle.

Development of a Numerical Model for Quasi-Periodic Forces of Two-Phase Cross Flow in Tube Bundles

2014 ◽  
Author(s):  
Sarra Zoghlami ◽  
Cédric Béguin ◽  
Stéphane Étienne
Keyword(s):  
Numerical Model ◽  
Tube Bundle ◽  
Cross Flow ◽  
Deep Understanding ◽  
Added Mass ◽  
Dispersed Phase ◽  
Two Phase ◽  
Induced Drag ◽  
Tube Bundles ◽  
Lagrange Approach

To reduce the damage caused by induced vibrations due to two-phase cross flow on tube bundles in heat exchangers, a deep understanding of the different sources of this phenomenon is required. For this purpose, a numerical model was previously developed to simulate the quasi periodic forces on the tube bundle due to two-phase cross flow. An Euler-Lagrange approach is adopted to describe the flow. The Euler approach describes the continuous phase (liquid) using potential flow. The dispersed phase is assumed to have no interaction on liquid flow. Based on visual observation, static vortices behind the tube are introduced. The Lagrange approach describes the dispersed phase (gas). The model allows bubbles to split up or to coalesce. The forces taken into account acting on the bubbles are the buoyancy, the drag and induced drag, the added mass and induced added mass and impact force (bubble-bubble and bubble-tube). Forces taken into account acting on the tubes are impact forces and induced drag and added mass forces. This model allows us to obtain quasi periodic force on tube induced by two-phase cross flow of relative good magnitude and frequency contains. The model still needs improvement to bring us closer to experimental data of force, for example by introducing a dependency between the void ratio and the intensity of the vortex and by taking into account the bubbles deformation.

Acoustic Resonance in Heat Exchanger Tube Bundles—Part I: Physical Nature of the Phenomenon

1987 ◽  
Vol 109 (3) ◽  
pp. 275-281 ◽  
Author(s):  
R. D. Blevins ◽  
M. M. Bressler
Keyword(s):  
Heat Exchanger ◽  
Gas Flow ◽  
Tube Bundle ◽  
Physical Nature ◽  
Transverse Mode ◽  
Acoustic Resonance ◽  
Heat Exchanger Tube ◽  
Sound Levels ◽  
Tube Bundles ◽  
Exchanger Tube

The intense acoustic resonance resulting from gas flow across a bank of heat exchanger tubes in a duct has been investigated experimentally and theoretically. At low gas velocities, the acoustic tone emanating from tube bundles increases in proportion to the flow velocity. When the frequency approaches a bound acoustic transverse mode of the tube bundle, intense sound can result. Sound levels as high as 173 db were measured within the bundle. During resonance, the sound correlates vortex shedding from the tubes and the pressure drop increases in some bundles.

Vibration of Tube Bundles in Two-Phase Cross-Flow: Part 2—Fluid-Elastic Instability

1989 ◽  
Vol 111 (4) ◽  
pp. 478-487 ◽  
Author(s):  
M. J. Pettigrew ◽  
J. H. Tromp ◽  
C. E. Taylor ◽  
B. S. Kim
Keyword(s):  
Tube Bundle ◽  
Cross Flow ◽  
Design Guidelines ◽  
Experimental Program ◽  
Elastic Instability ◽  
Two Phase ◽  
Critical Flow Velocity ◽  
Flexible Tube ◽  
Elastic Instabilities ◽  
Tube Bundles

An extensive experimental program was carried out to study the vibration behavior of tube bundles subjected to two-phase cross-flow. Fluid-elastic instability is discussed in Part 2 of this series of three papers. Four tube bundle configurations were subjected to increasing flow up to the onset of fluid-elastic instability. The tests were done on bundles with all-flexible tubes and on bundles with one flexible tube surrounded by rigid tubes. Fluid-elastic instabilities have been observed for all tube bundles and all flow conditions. The critical flow velocity for fluid-elastic instability is significantly lower for the all-flexible tube bundles. The fluid-elastic instability behavior is different for intermittent flows than for continuous flow regimes such as bubbly or froth flows. For continuous flows, the observed instabilities satisfy the relationship V/fd = K(2πζm/ρd2)0.5 in which the minimum instability factor K was found to be around 4 for bundles of p/d = 1.47 and significantly less for p/d = 1.32. Design guidelines are recommended to avoid fluid-elastic instabilities in two-phase cross-flows.

Self-Excited Acoustic Resonance of Isolated Cylinders in Cross-Flow

2012 ◽  
Vol 1 (1) ◽  
pp. 45-55 ◽  
Author(s):  
A. Mohany
Keyword(s):  
Flow Velocity ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Acoustic Resonance ◽  
Resonance Phenomenon ◽  
Flow Conditions ◽  
Resonance Mechanism ◽  
Single Cylinder ◽  
Tandem Cylinders ◽  
Tube Bundles

Self-excited acoustic resonance is a design concern in many engineering applications such as tube bundles of heat exchangers and boilers. Since this phenomenon is not yet fully understood, it can be dangerously unpredictable. Due to the complexity of the flow-sound interaction mechanisms in tube bundles, the simplified cases of a single cylinder and two cylinders in various arrangements, tandem and staggered, are investigated in some detail. A summary of these investigations is presented in the current paper. It is found that the aeroacoustic response of two-tandem and side-by-side cylinders in cross-flow can be considerably different from that of a single cylinder under similar flow conditions. Moreover, for the case of two tandem cylinders, the acoustic resonance is excited over two different ranges of flow velocity; the pre-coincidence and the coincidence resonance ranges. The pre-coincidence acoustic resonance phenomenon is found to be similar to the acoustic resonance mechanism of in-line tube bundles.

Flow-Excited Acoustic Resonance of Isolated Cylinders in Cross-Flow

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Nadim Arafa ◽  
Atef Mohany
Keyword(s):  
Particle Velocity ◽  
Acoustic Pressure ◽  
Excited Level ◽  
Cross Flow ◽  
Acoustic Resonance ◽  
Excitation Level ◽  
Linear Superposition ◽  
The Cross ◽  
Particle Velocities ◽  
Mode A

The flow-excited acoustic resonance of isolated cylinders in cross-flow is investigated experimentally where the effect of the cylinder(s) proximity to the acoustic particle velocity nodes of the cross-modes is presented in this paper. For the case of a single cylinder, the cylinder's location does not significantly affect the vortex shedding process; however, it affects the excitation level of each acoustic cross-mode. When the cylinder is moved away from the acoustic particle velocity antinode of a specific acoustic cross-mode, a combination of the cross-modes is excited with intensities that seem to be proportional to the ratio of the acoustic particle velocities of these modes at the cylinder's location. For the cases of two and three hydrodynamically uncoupled cylinders positioned simultaneously side-by-side in the duct, it is observed that the first three acoustic cross-modes are excited. When one cylinder is positioned at the acoustic particle velocity antinode of a specific cross-mode and another cylinder is positioned at its acoustic particle velocity node, i.e., a cylinder that should excite the resonance and another one that should not excite it, respectively; the excitation always takes over and the resonance occurs at a further elevated levels. It is also observed that the acoustic pressure levels in the cases of multiple cylinders are not resulting from a linear superposition of the excited level obtained from each individual cylinder which indicates that the removal of cylinders at certain locations may not be a viable technique to eliminate the acoustic resonance in the case of tube bundles.

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