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Sample records for acoustically induced vibration

  1. CFD Simulation of Acoustic-Induced Vibration in Main Steam Line of APR1400

    Lim, Sang Gyu; Kim, Tae Jun; Kim, Han Gon [Korea Hydro and Nuclear Power, Daejeon (Korea, Republic of)

    2012-05-15

    In recently, many boiling water reactors (BWRs) implement extended power uprate (EPU) to increase economic benefits. After EPU, Quad Cities power plant has been experienced damage of steam dryers due to acoustic-induced vibration. Acoustic resonance is produced by the interaction between the sound field and an unstable shear layer when the dry steam flows across the closed branch pipes such as safety relief valve(SRV). The unsteady vortices are separated at the leading edge of branch pipe and generated fluctuating pressure wave. After this experience, US-NRC issued that the licensee for new type of reactor should perform a vibration assessment program for an adverse flow effect in the main steam line in accordance with regulatory guideline 1.20 revision 3. In Korea, KHNP CRI implements comprehensive vibration program for steam generator of APR1400 and evaluates acoustic-induced vibration in main steam line using a commercial CFD code, ANSYS CFX 13.0. This paper deals with benchmark analysis to obtain applicability and reliability of commercial code for prediction of acoustic resonance phenomenon in case of single branch pipe test. Based on the benchmark analysis, analysis of main steam line in APR1400 plant is performed. In case of APR1400, five main steam safety valves are installed in the main steam line. Finally, this paper shows a prediction result of acoustic induced vibration characteristic in main steam system of APR1400

  2. Structural Acoustics and Vibrations

    Chaigne, Antoine

    This structural chapter is devoted to vibrations of structures and to their coupling with the acoustic field. Depending on the context, the radiated sound can be judged as desirable, as is mostly the case for musical instruments, or undesirable, like noise generated by machinery. In architectural acoustics, one main goal is to limit the transmission of sound through walls. In the automobile industry, the engineers have to control the noise generated inside and outside the passenger compartment. This can be achieved by means of passive or active damping. In general, there is a strong need for quieter products and better sound quality generated by the structures in our daily environment.

  3. Flow-induced vibration and acoustic behaviour of CANFLEX-LVRF bundles in a Bruce B NGS fuel channel

    Frequency/temperature sweep tests were performed in a high-temperature/high-pressure test channel to determine the acoustic and flow-induced vibration characteristics of the CANFLEX-LVRF bundle. The vibratory response of CANFLEX-LVRF bundles was compared with that of 37-element fuel bundles under Bruce B NGS fuel channel normal operating conditions. The tests were performed with a 12-bundle string of CANFLEX-LVRF bundles as well as a mixed string for the transition core. The tests showed that the LVRF bundles performed as required without failure or gross geometry changes. The mixed fuel strings behaved in a manner similar to that of a string of CANFLEX-LVRF bundles. (author)

  4. Influence of vocal fold stiffness and acoustic loading on flow-induced vibration of a single-layer vocal fold model

    Zhang, Zhaoyan; Neubauer, Juergen; Berry, David A.

    2009-04-01

    The flow-induced vibrations of a single-layer vocal fold model were investigated as a function of vocal fold stiffness, and subglottal and supraglottal acoustic loading. Previously, it was reported that the single-layer vocal fold model failed to vibrate when short, clinically relevant tracheal tubes were used. Moreover, it was reported that the model had a propensity to be acoustically driven, and aerodynamically driven vibration was observed only when a vertical restraint was applied superiorly to the vocal folds. However, in this study involving a wider range of source/tract conditions, the previous conclusions were shown to apply only for the special case of a stiff vocal fold model, for which self-oscillation occurred only when the vocal fold vibration synchronized to either a subglottal or supraglottal resonance. For a more general case, when vocal fold stiffness was decreased, the model did exhibit self-oscillation at short tracheal tubes, and no vertical restraint was needed to induce aerodynamically driven phonation. Nevertheless, the vocal fold vibration transitioned from aerodynamically driven to acoustically driven vibration when one of the subglottal resonance frequencies approximated one of the natural frequencies of the vocal folds. In this region, strong superior-inferior vibrations were observed, the phonation threshold pressure was significantly reduced, and the phonation onset frequency was heavily influenced by the dominant acoustic resonance. For acoustically driven phonation, a compliant subglottal system always lowered phonation threshold. However, an inertive vocal tract could either increase or decrease phonation threshold pressure, depending on the phonation frequency.

  5. Coupling between plate vibration and acoustic radiation

    Frendi, Abdelkader; Maestrello, Lucio; Bayliss, Alvin

    1992-01-01

    A detailed numerical investigation of the coupling between the vibration of a flexible plate and the acoustic radiation is performed. The nonlinear Euler equations are used to describe the acoustic fluid while the nonlinear plate equation is used to describe the plate vibration. Linear, nonlinear, and quasi-periodic or chaotic vibrations and the resultant acoustic radiation are analyzed. We find that for the linear plate response, acoustic coupling is negligible. However, for the nonlinear and chaotic responses, acoustic coupling has a significant effect on the vibration level as the loading increases. The radiated pressure from a plate undergoing nonlinear or chaotic vibrations is found to propagate nonlinearly into the far-field. However, the nonlinearity due to wave propagation is much weaker than that due to the plate vibrations. As the acoustic wave propagates into the far-field, the relative difference in level between the fundamental and its harmonics and subharmonics decreases with distance.

  6. Impact of flow induced vibration acoustic loads on the design of the Laguna Verde Unit 2 steam dryer

    Industry experience with Boiling Water Reactors (BWRs) has shown that increasing the steam flow through the main steam lines (MSLs) to implement an extended power up rate (EPU) may lead to amplified acoustic loads on the steam dryer, which may negatively affect the structural integrity of the component. The source of these acoustic loads has been found to be acoustic resonance of the side branches on the MSLs, specifically, coupling of the vortex shedding frequency and natural acoustic frequency of safety relief valves (SRVs). The resonance that results from this coupling can contribute significant acoustic energy into the MSL system, which may propagate upstream into the reactor pressure vessel steam dome and drive structural vibration of steam dryer components. This can lead to high-cycle fatigue issues. Lock-in between the vortex shedding frequency and SRV natural frequency, as well as the ability for acoustic energy to propagate into the MSL system, are a function of many things, including the plant operating conditions, geometry of the MSL/SRV junction, and placement of SRVs with respect to each other on the MSLs. Comision Federal de Electricidad and Westinghouse designed, fabricated, and installed acoustic side branches (ASBs) on the MSLs which effectively act in the system as an energy absorber, where the acoustic standing wave generated in the side-branch is absorbed and dissipated inside the ASB. These ASBs have been very successful in reducing the amount of acoustic energy which propagates into the steam dome. In addition, modifications to the Laguna Verde Nuclear Power Plant Unit 2 steam dryer have been completed to reduce the stress levels in critical locations in the dryer. The objective of this paper is to describe the acoustic side branch concept and the design iterative processes that were undertaken at Laguna Verde Unit 2 to achieve a steam dryer design that meets the guidelines of the American Society of Mechanical Engineers, Boiler and Pressure

  7. Impact of flow induced vibration acoustic loads on the design of the Laguna Verde Unit 2 steam dryer

    Forsyth, D. R.; Wellstein, L. F.; Theuret, R. C.; Han, Y.; Rajakumar, C. [Westinghouse Electric Company LLC, Cranberry Township, PA 16066 (United States); Amador C, C.; Sosa F, W., E-mail: forsytdr@westinghouse.com [Comision Federal de Electricidad, Central Nucleoelectrica Laguna Verde, Km 42.5 Carretera Cardel-Nautla, 91680 Alto Lucero, Veracruz (Mexico)

    2015-09-15

    Industry experience with Boiling Water Reactors (BWRs) has shown that increasing the steam flow through the main steam lines (MSLs) to implement an extended power up rate (EPU) may lead to amplified acoustic loads on the steam dryer, which may negatively affect the structural integrity of the component. The source of these acoustic loads has been found to be acoustic resonance of the side branches on the MSLs, specifically, coupling of the vortex shedding frequency and natural acoustic frequency of safety relief valves (SRVs). The resonance that results from this coupling can contribute significant acoustic energy into the MSL system, which may propagate upstream into the reactor pressure vessel steam dome and drive structural vibration of steam dryer components. This can lead to high-cycle fatigue issues. Lock-in between the vortex shedding frequency and SRV natural frequency, as well as the ability for acoustic energy to propagate into the MSL system, are a function of many things, including the plant operating conditions, geometry of the MSL/SRV junction, and placement of SRVs with respect to each other on the MSLs. Comision Federal de Electricidad and Westinghouse designed, fabricated, and installed acoustic side branches (ASBs) on the MSLs which effectively act in the system as an energy absorber, where the acoustic standing wave generated in the side-branch is absorbed and dissipated inside the ASB. These ASBs have been very successful in reducing the amount of acoustic energy which propagates into the steam dome. In addition, modifications to the Laguna Verde Nuclear Power Plant Unit 2 steam dryer have been completed to reduce the stress levels in critical locations in the dryer. The objective of this paper is to describe the acoustic side branch concept and the design iterative processes that were undertaken at Laguna Verde Unit 2 to achieve a steam dryer design that meets the guidelines of the American Society of Mechanical Engineers, Boiler and Pressure

  8. Analysis of Vibration and Acoustic Radiation of Submarine Hull Induced by Longitudinal Vibration of Propulsion Shafting%推进轴系纵向振动引起的艇体声振特性分析

    张赣波; 赵耀

    2012-01-01

    The pulsatile thrust of propeller induced by asymmetrical wake field can cause longitudinal vibration of the propulsion shafting. The vibration will transmit through the shafting, thrust bearing and foundation to the submarine hull, and induce the low frequency underwater acoustic radiation of the hull. Considering the coupled effect of shafting, foundation and the hull, the structural model of the propulsion shafting was established. The propulsion shafting -submarine hull coupled vibration was analyzed, and the acoustic radiation field of the hull was calculated by FEM/BEM based on the mode superposition method. The results show that the longitudinal vibration mode is one of main modes which participates the acoustic radiation. By instilling a dynamic vibration absorber between the thrust bearing and its foundation, the transmission of longitudinal vibration to the hull can be decreased. The acoustic radiation of hull induced by longitudinal vibration of propulsion shafting can be controlled.%螺旋桨在艇体艉部不均匀伴流场中旋转产生的脉动推力激励起推进轴系纵向振动,振动经推力轴承基座传递至艇体,引起艇体水下低频辐射噪声.通过建立推进轴系、推力轴承基座和艇体耦合结构模型,分析推进轴系—艇体的耦合振动模态,结果显示,艇体弹性支撑边界条件对推进轴系的纵向振动特性有一定影响.采用基于模态叠加法的有限元结合边界元方法分析推进轴系纵向振动激励下的艇体水下辐射声场,分析表明,艇体第1阶纵向振动模态是参与艇体水下声辐射的主模态.进一步在推力轴承及其基座间安装动力吸振器以减小推进轴系纵向振动向艇体的传递,使艇体水下辐射噪声得到一定程度上的控制.

  9. Adaptive structural vibration control of acoustic deflector

    Ostasevicius, Vytautas; Palevicius, Arvydas; Ragulskis, Minvydas; Dagys, Donatas; Janusas, Giedrius

    2004-06-01

    Vehicle interior acoustics became an important design criterion. Both legal restrictions and the growing demand for comfort, force car manufacturers to optimize the vibro-acoustic behavior of their products. The main source of noise is, of course, the engine, but sometimes some ill-designed cover or other shell structure inside the car resonates and makes unpredicted noise. To avoid this, we must learn the genesis mechanism of such vibrations, having as subject complex 3D shells. The swift development of computer technologies opens the possibility to numerically predict and optimize the vibrations and noises.

  10. Surface Acoustic Wave (SAW Vibration Sensors

    Jerzy Filipiak

    2011-12-01

    Full Text Available In the paper a feasibility study on the use of surface acoustic wave (SAW vibration sensors for electronic warning systems is presented. The system is assembled from concatenated SAW vibration sensors based on a SAW delay line manufactured on a surface of a piezoelectric plate. Vibrations of the plate are transformed into electric signals that allow identification of the sensor and localization of a threat. The theoretical study of sensor vibrations leads us to the simple isotropic model with one degree of freedom. This model allowed an explicit description of the sensor plate movement and identification of the vibrating sensor. Analysis of frequency response of the ST-cut quartz sensor plate and a damping speed of its impulse response has been conducted. The analysis above was the basis to determine the ranges of parameters for vibrating plates to be useful in electronic warning systems. Generally, operation of electronic warning systems with SAW vibration sensors is based on the analysis of signal phase changes at the working frequency of delay line after being transmitted via two circuits of concatenated four-terminal networks. Frequencies of phase changes are equal to resonance frequencies of vibrating plates of sensors. The amplitude of these phase changes is proportional to the amplitude of vibrations of a sensor plate. Both pieces of information may be sent and recorded jointly by a simple electrical unit.

  11. Acoustic vibration induced high electromagnetic responses of Fe3O4 nano-hollow spheres in the THz regime

    Herein, we investigate the origin of enhanced absorption and complex conductivity of magnetite (Fe3O4) nano-hollow spheres (NHSs) in contrast to its nanoparticles (NPs) configuration in the frequency range 0.4–2.0 THz. The maximum absorption for NHSs and NPs of the same average diameter (∼100 nm) are found to be 246.27 and 48.35 cm−1 at 1.8 THz, respectively. A detailed study suggests that the multiple resonance peaks in the absorption spectra are due to low frequency acoustic vibrational phonon modes of Fe3O4 nanostructures. Moreover, we demonstrate that the magnitude of total absorption can be tailored by varying the shell thickness of NHSs. It is found to increase with increasing shell thickness, and attain a maximum value of 498.5 cm−1 for the NHSs of average diameter 350 nm at 1.8 THz. The invariance of frequency dependent magnetic permeability points out that the absorption is basically due to dielectric loss instead of magnetic loss. The enhanced THz conductivity of Fe3O4 NHSs, as compared to NPs is described in light of thermally activated polaronic hopping which is found to increase with increasing THz absorption. Finally, the size dependent THz conductivity of NHSs confirms its sole dependence on the magnitude of THz absorptivity. (paper)

  12. Numerical simulation of flow induced airfoil vibrations

    Sváček, P.; Feistauer, M.; Horáček, Jaromír

    Vol. II. Paříž : Ecole Polytechnique, Paris, 2004 - (Langre, E.; Axisa, F.), s. 57-62 ISBN 2-7302-1141-1. [International Conference on Flow Induced Vibration - FIV 2004 /8./. Paříž (FR), 06.07.2004-09.07.2004] R&D Projects: GA ČR GA101/02/0391 Institutional research plan: CEZ:AV0Z2076919 Keywords : unsteady Navier-Stokes equations * nonlinear aeroelasticity * postcritical vibrations Subject RIV: BI - Acoustics

  13. Acoustics and vibration comfort; Akustik und Schwingungskomfort

    Penne, Filip; Mueller, Torsten [BMW Group, Muenchen (Germany). Akustik und Schwingungskomfort fuer die mittlere und grosse Modellreihe

    2008-11-15

    With the new BMW 7 Series, BMW is continuing its success story in the luxury class. Within the BMW product portfolio, the 7 Series is the pinnacle in terms of vehicle dynamics, fuel consumption and comfort. This unique combination of efficient dynamics on one hand and an extremely convincing level of comfort on the other hand comprises the character of this automobile. Vehicle acoustics and vibration comfort make a significant contribution towards the overall impression of ''sheer driving pleasure''. (orig.)

  14. Organ pipe resonance induced vibration in piping system

    Acoustic-induced vibration is a fluid-structure interaction phenomenon. The feedback mechanism between the acoustic pressure pulsation and the structure movements determines the excited acoustic modes which, in turn, amplify the structure response when confidence frequency and mode shape matching occurs. The acoustic modes are not determined from the acoustic boundary conditions alone, structure feedback is as responsible for determining the acoustic modes and shaping the resulting forcing functions. Acoustic-induced piping vibration, when excited, does not attenuate much with distance. Pressure pulsation can be transmitted throughout the piping system and its branch connections. It is this property that makes vibration monitoring difficult, because vibration can surface at locations far away from the acoustic source when resonance occurs. For a large piping system with interconnected branches, the monitoring task can be formidable, particularly when there is no indication what the real source is. In organ pipe resonance induced vibration, the initiating acoustic source may be inconspicuous or unavoidable during operation. In these situations, the forcing function approach can offer an optimal tool for vibration assessment. The forcing function approach was used in the evaluation of a standby steam piping vibration problem. Monitoring locations and instrument specifications were determined from the acoustic eigenfunction profiles. Measured data confirmed the presence of coherent vibrations in the large bore piping. The developed forcing function permits design evaluation of the piping system, which leads to remedial actions and enables fatigue life determination, thus providing confidence to system operation. The forcing function approach is shown to be useful in finding potential vibration area and verifying the integrity of weak structure links. Application is to steam lines at BWR plants

  15. Materials for Damping Ambient Acoustic and Vibration Signals Project

    National Aeronautics and Space Administration — Long-term exposure to even relatively low levels of acoustic and vibration signals has been shown to be potentially harmful to humans. A new class of piezoelectric...

  16. Research on modal analysis of structural acoustic radiation using structural vibration modes and acoustic radiation modes

    LI Sheng; ZHAO Deyou

    2004-01-01

    Modal analysis of structural acoustic radiation from a vibrating structure is discussed using structural vibration modes and acoustic radiation modes based on the quadratic form of acoustic power. The finite element method is employed for discretisizing the structure.The boundary element method and Rayleigh integral are used for modeling the acoustic fluid.It is shown that the power radiated by a single vibration mode is to increase the radiated power and the effect of modal interaction can lead to an increase or a decrease or no change in the radiated power, moreover, control of vibration modes is a good way to reduce both vibration and radiated sound as long as the influence of interaction of vibration modes on sound radiation is insignificant. Stiffeners may change mode shapes of a plate and thus change radiation efficiency of the plate's modes. The CHIEF method is adopted to obtain an acoustic radiation mode formulation without the nonuniqueness difficulty at critical frequencies for three-dimensional structures by using Moore-Penrose inverse. A pulsating cube is involved to verify the formulation. Good agreement is obtained between the numerical and analytical solutions. The shapes and radiation efficiencies of acoustic radiation modes of the cube are discussed. The structural acoustic control using structural vibration modes and acoustic radiation modes are compared and studied.

  17. Natural vibration of a spherical shell with an acoustical medium

    Zolotarev, Igor

    GarmischPartenkirchen: XX, 2000, s. 5-10. [Proceedings of international congress on Sound and vibrations /7./.. Garmisch-Partenkirchen (NE), 04.07.2000-07.07.2000] R&D Projects: GA ČR GV106/98/K019 Keywords : spherical shell * acoustical medium Subject RIV: BI - Acoustics

  18. Vertical vibration and shape oscillation of acoustically levitated water drops

    Geng, D. L.; Xie, W. J.; Yan, N.; Wei, B.

    2014-09-01

    We present the vertical harmonic vibration of levitated water drops within ultrasound field. The restoring force to maintain such a vibration mode is provided by the resultant force of acoustic radiation force and drop gravity. Experiments reveal that the vibration frequency increases with the aspect ratio for drops with the same volume, which agrees with the theoretical prediction for those cases of nearly equiaxed drops. During the vertical vibration, the floating drops undergo the second order shape oscillation. The shape oscillation frequency is determined to be twice the vibration frequency.

  19. Vertical vibration and shape oscillation of acoustically levitated water drops

    Geng, D. L.; Xie, W. J.; Yan, N.; Wei, B., E-mail: bbwei@nwpu.edu.cn [Department of Applied Physics, Northwestern Polytechnical University, Xi' an 710072 (China)

    2014-09-08

    We present the vertical harmonic vibration of levitated water drops within ultrasound field. The restoring force to maintain such a vibration mode is provided by the resultant force of acoustic radiation force and drop gravity. Experiments reveal that the vibration frequency increases with the aspect ratio for drops with the same volume, which agrees with the theoretical prediction for those cases of nearly equiaxed drops. During the vertical vibration, the floating drops undergo the second order shape oscillation. The shape oscillation frequency is determined to be twice the vibration frequency.

  20. Acoustical comfort of vehicles: A combination of sound and vibration

    Genuit, Klaus; Schutte-Fortkamp, Brigitte; Fiebig, Andre

    2005-09-01

    As vehicles become more and more quiet, the customer's sensitivity to acoustical comfort increases. The acoustical comfort is not independent of the vibrations the driver can feel in the seat and at the steering. The passenger of a vehicle must be regarded as part of a vibro-acoustic system. Correspondingly, the subjective judgement which passengers make about their impression of levels of acoustic comfort encompasses both sound and vibration. Achievement in this field depends on obtaining knowledge about the interaction between sound and vibration and how these factors impact subjective evaluation. To save time and money prediction tools for the estimation of sound and vibration contributions into the vehicle cabin are very important in order to simulate the final comfort with respect to sound and vibration. Based on the binaural transfer path analysis in combination with the binaural transfer path synthesis a sound and vibration reproduction in a so-called SoundCar can be realized with a very good simulation of a real situation of a car. First research tests completed for the European research project OBELICS (Objective Evaluation of Interior Car Sound) have shown that the use of SoundCar may result in more reliable sound characteristic and quality evaluation.

  1. Vibration and Acoustic Radiation from Submerged Spherical Double-Shell

    陈军明; 黄玉盈; 陈应波

    2003-01-01

    Based on the motion differential equations of vibration and acoustic coupling system for a thin elastic spherical double-shell with several elastic plates attached to the shells, in which Dirac-δ functions are employed to introduce the forces and moments applied by the attachments, and by means of expanding field quantities as the Legendre series, a semi-analytic solution is derived for the solution to the vibration and acoustic radiation from a submerged spherical double-shell. This solution has a satisfying computational effectiveness and precision for arbitrary frequency range excitation. It is concluded that the internal plates attached to shells can change significantly the mechanical and acoustical characteristics of shells, and make the coupling system have a very rich resonance frequency spectrum. Moreover, the present method can be used to study the acoustic radiation mechanism of the type of structure.

  2. Active elastic metamaterials with applications in vibration and acoustics

    Pope, Simon A.; Laalej, Hatim; Daley, Stephen; Reynolds, Matthew

    2012-01-01

    Elastic metamaterials provide a new approach to solving existing problems in vibration and acoustics. They have also been associated with novel concepts such as acoustic invisibility and subwavelength imaging. To be applied to many of the proposed applications a metamaterial would need to have the desired mass density and elastic moduli over a prescribed frequency band. Importantly active metamaterials provide a degree of adaptability. This paper will focus on extending a previous theoretical...

  3. Chaotic vortex induced vibrations

    Zhao, J.; Sheridan, J. [Fluids Laboratory for Aeronautical and Industrial Research (FLAIR), Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, Victoria 3800 (Australia); Leontini, J. S. [Department of Mechanical and Product Design Engineering, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia); Lo Jacono, D. [Institut de Mécanique des Fluides de Toulouse (IMFT), CNRS, UPS and Université de Toulouse, 31400 Toulouse (France)

    2014-12-15

    This study investigates the nature of the dynamic response of an elastically mounted cylinder immersed in a free stream. A novel method is utilized, where the motion of the body during a free vibration experiment is accurately recorded, and then a second experiment is conducted where the cylinder is externally forced to follow this recorded trajectory. Generally, the flow response during both experiments is identical. However, particular regimes exist where the flow response is significantly different. This is taken as evidence of chaos in these regimes.

  4. Numerical Simulation of Airfoil Vibrations Induced by Turbulent Flow

    Feistauer, M.; Horáček, Jaromír; Sváček, P.

    2015-01-01

    Roč. 17, č. 1 (2015), s. 146-188. ISSN 1815-2406 R&D Projects: GA ČR(CZ) GAP101/11/0207 Institutional support: RVO:61388998 Keywords : fluid-structure interaction * flow induced vibrations * turbulence models * finite element method Subject RIV: BI - Acoustics Impact factor: 1.943, year: 2014

  5. Assessing the severity of fatigue crack using acoustics modulated by hysteretic vibration for a cantilever beam

    He, Qingbo; Lin, Yin

    2016-05-01

    This paper investigates fatigue crack severity assessment using acoustics modulated by hysteretic vibration for a cantilever beam. In this study, a nonlinear oscillator system is constructed to induce the hysteretic frequency response of the cantilever beam in dynamics, and the hysteretic vibration is then used to modulate the acoustic waves to generate the vibro-acoustic modulation (VAM) effect. Through modulation of hysteretic vibration, the hysteretic response of the VAM can be achieved. The experimental results further validated that the VAM hysteresis phenomenon can be enhanced with the increase of crack severity owing to the change of beam's effective stiffness. Simulations in the proposed physical model explained the reason of enhancement of hysteresis phenomenon. Combined with nonlinear bistable structural model, a fatigue crack severity assessment approach was proposed by evaluating the hysteretic region (e.g., bandwidth or jumping frequency) in the vibration frequency response of the VAM effect. The reported study is valuable in building a monotonic relationship to assess the severity of fatigue crack by a nonlinear acoustics approach.

  6. Man-Induced Vibrations

    Jönsson, Jeppe; Hansen, Lars Pilegaard

    1994-01-01

    Human motion can cause various types of periodic or transient dynamic loads. The periodic loads are mainly due to jumping, running, dancing, walking and body rocking. Transient loads primarily result from single impulse loads, such as jumping and falling from elevated positions. The response...... to these loads are of primary interest for the structural engineer, whereas the exact load as a function of time generally is of minor importance. This is true when the loading time (contact duration) tp is smal1 compared to the largest natura1 periods Tn = 2π/ωn of the structure. The present study is mainly...... work has been done on the measurement of the exact load functions and related reponse analysis. A recent work using a spectral description has been performed by Per-Erik Erikson and includes a good literature survey. Bachmann and Ammann give a good overview of vibrations caused by human activity. Other...

  7. Measurement of vibration, flow and acoustic characteristics

    Horáček, Jaromír; Bula, Vítězslav; Veselý, Jan

    Plzeň : University of West Bohemia, 2012 - (Adámek, V.; Zajíček, M.; Jonášová, A.). s. 1-2 ISBN 978-80-261-0157-4. [Computational mechanics 2012 /28./. 12.11.2012-14.11.2012, Špičák] R&D Projects: GA ČR GAP101/12/1306 Institutional research plan: CEZ:AV0Z20760514 Keywords : biomechanics of voice * impact stress * voice production modelling Subject RIV: BI - Acoustics

  8. Acoustically-Induced Electrical Signals

    Brown, S. R.

    2014-12-01

    We have observed electrical signals excited by and moving along with an acoustic pulse propagating in a sandstone sample. Using resonance we are now studying the characteristics of this acousto-electric signal and determining its origin and the controlling physical parameters. Four rock samples with a range of porosities, permeabilities, and mineralogies were chosen: Berea, Boise, and Colton sandstones and Austin Chalk. Pore water salinity was varied from deionized water to sea water. Ag-AgCl electrodes were attached to the sample and were interfaced to a 4-wire electrical resistivity system. Under computer control, the acoustic signals were excited and the electrical response was recorded. We see strong acoustically-induced electrical signals in all samples, with the magnitude of the effect for each rock getting stronger as we move from the 1st to the 3rd harmonics in resonance. Given a particular fluid salinity, each rock has its own distinct sensitivity in the induced electrical effect. For example at the 2nd harmonic, Berea Sandstone produces the largest electrical signal per acoustic power input even though Austin Chalk and Boise Sandstone tend to resonate with much larger amplitudes at the same harmonic. Two effects are potentially responsible for this acoustically-induced electrical response: one the co-seismic seismo-electric effect and the other a strain-induced resistivity change known as the acousto-electric effect. We have designed experimental tests to separate these mechanisms. The tests show that the seismo-electric effect is dominant in our studies. We note that these experiments are in a fluid viscosity dominated seismo-electric regime, leading to a simple interpretation of the signals where the electric potential developed is proportional to the local acceleration of the rock. Toward a test of this theory we have measured the local time-varying acoustic strain in our samples using a laser vibrometer.

  9. Surface Acoustic Wave Vibration Sensors for Measuring Aircraft Flutter

    Wilson, William C.; Moore, Jason P.; Juarez, Peter D.

    2016-01-01

    Under NASA's Advanced Air Vehicles Program the Advanced Air Transport Technology (AATT) Project is investigating flutter effects on aeroelastic wings. To support that work a new method for measuring vibrations due to flutter has been developed. The method employs low power Surface Acoustic Wave (SAW) sensors. To demonstrate the ability of the SAW sensor to detect flutter vibrations the sensors were attached to a Carbon fiber-reinforced polymer (CFRP) composite panel which was vibrated at six frequencies from 1Hz to 50Hz. The SAW data was compared to accelerometer data and was found to resemble sine waves and match each other closely. The SAW module design and results from the tests are presented here.

  10. Laser method of acoustical emission control from vibrating surfaces

    Motyka, Zbigniew

    2013-01-01

    For limitation of the noise in environment, the necessity occurs of determining and location of sources of sounds emitted from surfaces of many machines and devices, assuring in effect the possibility of suitable constructional changes implementation, targeted at decreasing of their nuisance. In the paper, the results of tests and calculations are presented for plane surface sources emitting acoustic waves. The tests were realized with the use of scanning laser vibrometer which enabled remote registration and the spectral analysis of the surfaces vibrations. The known hybrid digital method developed for determination of sound wave emission from such surfaces divided into small finite elements was slightly modified by distinguishing the phase correlations between such vibrating elements. The final method being developed may find use in wide range of applications for different forms of vibrations of plane surfaces.

  11. Coupling of Acoustic Vibrations to Plasmon Resonances in Metal Nanoparticles

    Ahmed, Aftab; Pelton, Matthew; Guest, Jeffrey

    Measurements of acoustic vibrations in nanoparticles provide a unique opportunity to study mechanical phenomena at nanometer length scales and picosecond time scales. Phonon vibrations of plasmonic nanoparticles are of particular interest, due to their large extinction efficiencies, and high sensitivity to surrounding medium. There are two mechanisms that transduce the mechanical oscillations into plasmon resonance shift: (1) changes in polarizability; and (2) changes in electron density. These mechanisms have been used to explain qualitatively the origin of the transient-absorption signals, however, a quantitative connection has not yet been made except for simple geometries. Here, we present a method to quantitatively determine the coupling between vibrational modes and plasmon modes in noble-metal nanoparticles including spheres, shells, rods and cubes. We separately determine the parts of the optical response that are due to shape changes and to changes in electron density, and we relate the optical signals to the symmetries of the vibrational and plasmon modes. These results clarify reported experimental results, and should help guide the optimization of future experiments.

  12. CRBRP flow induced vibration program

    The program to assure the structural adequacy of Clinch River Breeder Reactor (CRBRP) components during its planned 30 years of operation is described. The program includes (1) an assessment of reactor components relative to their susceptibility to FIV, (2) designing to minimize component excitation due to Fluid induced vibrations (FIV), (3) scale model tests to measure structural response during simulated operating conditions and (4) preoperational tests. An overview of the CRBRP test program is described. Additionally, details of scale model testing of reactor internals and the steam generator is described in more detail. (author)

  13. Acoustic Pressure Waves in Vibrating 3-D Laminated Beam-Plate Enclosures

    Charles A. Osheku

    2009-01-01

    Full Text Available The effect of structural vibration on the propagation of acoustic pressure waves through a cantilevered 3-D laminated beam-plate enclosure is investigated analytically. For this problem, a set of well-posed partial differential equations governing the vibroacoustic wave interaction phenomenon are formulated and matched for the various vibrating boundary surfaces. By employing integral transforms, a closed form analytical expression is computed suitable for vibroacoustic modeling, design analysis, and general aerospace defensive applications. The closed-form expression takes the form of a kernel of polynomials for acoustic pressure waves showing the influence of linear interface pressure variation across the axes of vibrating boundary surfaces. Simulated results demonstrate how the mode shapes and the associated natural frequencies can be easily computed. It is shown in this paper that acoustic pressure waves propagation are dynamically stable through laminated enclosures with progressive decrement in interfacial pressure distribution under the influence of high excitation frequencies irrespective of whether the induced flow is subsonic, sonic , supersonic, or hypersonic. Hence, in practice, dynamic stability of hypersonic aircrafts or jet airplanes can be further enhanced by replacing their noise transmission systems with laminated enclosures.

  14. Characteristics of Vibration Induced by Cavitation

    WANG Guo-yu; TAO Lei; LIU Shu-yan; QIAN Jian-jun

    2005-01-01

    Cavitation-induced vibration characteristics and the relations between the vibration and cavitation are studied. Cavitation vibrations are measured around a model hollow-jet valve by an accelerometer under cavitating and non-cavitating conditions. The measurement data is analyzed by FFT method. The corresponding cavitating flow patterns are photographed by a high-speed camera with an xenon flash lamp. The frequency band of the vibration induced by cavitation is determined. To compare the vibration intensities under different cavitation conditions, a definition of vibration acceleration level is introduced based on power spectral density of the vibration. By the analysis of vibration, the definitions of characteristic cavitation number are suggested. According to these cavitation numbers, the cavitation process is divided into three stages, that is, incipient cavitation, subcavitation and supercavitation.

  15. Acoustic and Vibration Control for an Underwater Structure under Mechanical Excitation

    Shi-Jian Zhu

    2014-01-01

    Full Text Available Acoustic and vibration control for an underwater structure under mechanical excitation has been investigated by using negative feedback control algorithm. The underwater structure is modeled with cylindrical shells, conical shells, and circular bulkheads, of which the motion equations are built with the variational approach, respectively. Acoustic property is analyzed by the Helmholtz integration formulation with boundary element method. Based on negative feedback control algorithm, a control loop with a coupling use of piezoelectric sensor and actuator is built, and accordingly some numerical examples are carried out on active control of structural vibration and acoustic response. Effects of geometrical and material parameters on acoustic and vibration properties are investigated and discussed.

  16. Vibration-Induced Droplet Atomization

    Smith, M. K.; James, A.; Vukasinovic, B.; Glezer, A.

    1999-01-01

    Thermal management is critical to a number of technologies used in a microgravity environment and in Earth-based systems. Examples include electronic cooling, power generation systems, metal forming and extrusion, and HVAC (heating, venting, and air conditioning) systems. One technique that can deliver the large heat fluxes required for many of these technologies is two-phase heat transfer. This type of heat transfer is seen in the boiling or evaporation of a liquid and in the condensation of a vapor. Such processes provide very large heat fluxes with small temperature differences. Our research program is directed toward the development of a new, two-phase heat transfer cell for use in a microgravity environment. In this paper, we consider the main technology used in this cell, a novel technique for the atomization of a liquid called vibration-induced droplet atomization. In this process, a small liquid droplet is placed on a thin metal diaphragm that is made to vibrate by an attached piezoelectric transducer. The vibration induces capillary waves on the free surface of the droplet that grow in amplitude and then begin to eject small secondary droplets from the wave crests. In some situations, this ejection process develops so rapidly that the entire droplet seems to burst into a small cloud of atomized droplets that move away from the diaphragm at speeds of up to 50 cm/s. By incorporating this process into a heat transfer cell, the active atomization and transport of the small liquid droplets could provide a large heat flux capability for the device. Experimental results are presented that document the behavior of the diaphragm and the droplet during the course of a typical bursting event. In addition, a simple mathematical model is presented that qualitatively reproduces all of the essential features we have seen in a burst event. From these two investigations, we have shown that delayed droplet bursting results when the system passes through a resonance

  17. Effects of boundary conditions on vibrating mode of acoustic logging dipole transducer

    2008-01-01

    Acoustic transducer is an important part of acoustic well logging tool. In this paper,ANSYS software package is used to design acoustic dipole transducer and simulate vibrating mode of the dipole transducer in different mechanical boundary conditions. The results show that boundary conditions influence the number of vibrating mode in the same frequency band and the frequency value of the same vibrating mode. Several acoustic dipole transducers are designed according to the results of numerical simulation and laboratory measurements. The basic frequency of vibrating mode of experi-ment has good agreement with that of simulation. The numerical simulation plays a good guidance role in designing,producing and correctly installing the acoustic dipole transducer.

  18. Flow induced vibrations of piping system (Vibration sources - Mechanical response of the pipes)

    In order to design the supports of piping system, an estimation of the vibration induced by the fluid conveyed through the pipes are generally needed. For that purpose it is necessary. To evaluate the power spectra of all the main sources generated by the flow. These sources are located at the singular points of the circuit (enlargements, bends, valves, etc. ...). To calculate the modal parameters of fluid containing pipes. This paper presents: a methodical study of the most current singularities. Inter-correlation spectra of local pressure fluctuation downstream from the singularity and correlation spectra of associated acoustical sources have been measured. A theory of noise generation by unsteady flow in internal acoustics has been developed. All these results are very useful for evaluating the source characteristics in most practical pipes. A comparison between the calculation and the results of an experimental test has shown a good agreement

  19. Enhanced vibration based energy harvesting using embedded acoustic black holes

    Zhao, L.; Semperlotti, F.; Conlon, S. C.

    2014-03-01

    In this paper, we investigate the use of dynamic structural tailoring via the concept of an Acoustic Black Hole (ABH) to enhance the performance of piezoelectric based energy harvesting from operational mechanical vibrations. The ABH is a variable thickness structural feature that can be embedded in the host structure allowing a smooth reduction of the phase velocity while minimizing the amplitude of reflected waves. The ABH thickness variation is typically designed according to power-law profiles. As a propagating wave enters the ABH, it is progressively slowed down while its wavelength is compressed. This effect results in structural areas with high energy density that can be exploited effectively for energy harvesting. The potential of ABH for energy harvesting is shown via a numerical study based on fully coupled finite element electromechanical models of an ABH tapered plate with surface mounted piezo-transducers. The performances of the novel design are evaluated by direct comparison with a non-tapered structure in terms of energy ratios and attenuation indices. Results show that the tailored structural design allows a drastic increase in the harvested energy both for steady state and transient excitation. Performance dependencies of key design parameters are also investigated.

  20. Prediction of induced vibrations in stall

    Thirstrup Petersen, J.; Thomsen, K.; Aagaard Madsen, H. [Risoe National Lab., Wind Energy and Atmospheric Physics Dept., Roskilde (Denmark)

    1999-03-01

    The main results from recent research in stall induced vibrations are presented. The focus is on the edgewise blade vibrations, which during the last decade have turned out to be a potential threat against the stable operation of stall regulated wind turbines and a fact, which must be dealt with by the designer. The basic physical explanation for the phenomenon and examples of design precaution, which can be taken, are presented. (au)

  1. Damping Evaluation for Free Vibration of Spherical Structures in Elastodynamic-Acoustic Interaction

    Joumaa, Hady k

    2016-01-01

    This paper discusses the free vibration of elastic spherical structures in the presence of an externally unbounded acoustic medium. In this vibration, damping associated with the radiation of energy from the confined solid medium to the surrounding acoustic medium is observed. Evaluating the coupled system response (solid displacement and acoustic pressure) and characterizing the acoustic radiation damping in conjunction with the media properties are the main objectives of this research. In this work, acoustic damping is demonstrated for two problems: the thin spherical shell and the solid sphere. The mathematical approach followed in solving these coupled problems is based on the Laplace transform method. The linear under-damped harmonic oscillator is the reference model for damping estimation. The damping evaluation is performed in frequency as well as in time domains; both investigations lead to identical damping factor expressions.

  2. Flow induced vibration in pump impellers

    The complex nature of flow-induced vibration (FIV) has led prominent researchers in the field to conclude that it is extremely important to understand the flow-induced vibration mechanism in order to design out of the problem (DOP), rather than to attempt to design the problem area on the basis of analysis with a high degree of certitude (i.e., predicting system response). Designing out of the problem may not be affected by addressing one parameter but rather several: structural contour, material selection, flow properties, structural stiffness, damping, and fluid-structure coupling In this paper the mechanism of flow induced vibration fatigue failure of large circulating water pumps is discussed. This paper provides an overview of the inter-relationship of finite element and theoretical analysis, component and material testing, operational data, fabrication, and repair practices

  3. The statistical distributed source boundary point method to calculate the acoustic radiation from the random vibrating body

    WANGXiufeng; CHENXinzhao; LIUZhao

    2003-01-01

    The statistical distributed source boundary point method (SDSBPM) put forward is applied to calculate the acoustic radiation from the random vibrating body. A detailed description of this method is presented. A test for the SDSBPM is carried out through the random vibrating sphere and the random vibrating cuboid. An experiment on the exterior acoustic radiation of a random vibrating simulation axial box of the lathe tool is performed in a semi-anechoic chamber.

  4. Structural Design Optimization On Thermally Induced Vibration

    The numerical method of design optimization for structural thermally induced vibration is originally studied in this paper and implemented in application software JIFEX. The direct and adjoint methods of sensitivity analysis for thermal induced vibration coupled with both linear and nonlinear transient heat conduction is firstly proposed. Based on the finite element method, the structural linear dynamics is treated simultaneously with coupled linear and nonlinear transient heat structural linear dynamics is treated simultaneously with coupled linear and nonlinear transient heat conduction. In the thermal analysis model, the nonlinear heat conduction considered is result from the radiation and temperature-dependent materials. The sensitivity analysis of transient linear and nonlinear heat conduction is performed with the precise time integration method. And then, the sensitivity analysis of structural transient dynamics is performed by the Newmark method. Both the direct method and the adjoint method are employed to derive the sensitivity equations of thermal vibration, and there are two adjoint vectors of structure and heat conduction respectively. The coupling effect of heat conduction on thermal vibration in the sensitivity analysis is particularly investigated. With coupling sensitivity analysis, the optimization model is constructed and solved by the sequential linear programming or sequential quadratic programming algorithm. The methods proposed have been implemented in the application software JIFEX of structural design optimization, and numerical examples are given to illustrate the methods and usage of structural design optimization on thermally induced vibration

  5. Acoustic Levitation Transportation of Small Objects Using a Ring-type Vibrator

    Thomas, Gilles P. L.; Andrade, Marco A. B.; Adamowski, Julio C.; Silva, Eḿílio C. N.

    A new device for noncontact transportation of small solid objects is presented here. Ultrasonic flexural vibrations are generated along the ring shaped vibrator using two Langevin transducers and by using a reflector parallel to the vibrator, small particles are trapped at the nodal points of the resulting acoustic standing wave. The particles are then moved by generating a traveling wave along the vibrator, which can be done by modulating the vibration amplitude of the transducers. The working principle of the traveling wave along the vibrator has been modeled by the superposition of two orthogonal standing waves, and the position of the particles can be predicted by using finite element analysis of the vibrator and the resulting acoustic field. A prototype consisting of a 3 mm thick, 220 mm long, 50 mm wide and 52 mm radius aluminum ring-type vibrator and a reflector of the same length and width was built and small polystyrene spheres have been successfully transported along the straight parts of the vibrator.

  6. Stochastic analysis of self-induced vibrations

    Rüdinger, Finn; Krenk, Steen

    Vortex-induced vibrations of a structurl element are modelled as a non-linear stochastic single-degree-of-freedom system. The deterministic part of the governing equation represents laminar flow conditions with a stationary non-zero solution corresponding to lock-in. Across-wind turbulence is...

  7. Stochastic analysis of self-induced vibrations

    Rüdinger, Finn; Krenk, Steen

    2002-01-01

    Vortex-induced vibrations of a structurl element are modelled as a non-linear stochastic single-degree-of-freedom system. The deterministic part of the governing equation represents laminar flow conditions with a stationary non-zero solution corresponding to lock-in. Across-wind turbulence is...

  8. Analyses of Acoustic Streaming Generated by Four Ultrasonic Vibrators in a Vessel

    Nakagawa, Masafumi

    2004-05-01

    When ultrasonic waves are applied, the heat transfer at a heated surface in water increases markedly. The origin of this increase in heat transfer is thought to be due to the agitation effect from the microjets of cavitation and from acoustic streaming. The method in which four vibrators are used has the ability of further enhancing heat transfer. This paper presents the method using four vibrators to eject an acoustic stream jet at a selected position in the vessel. Analyses of this method are performed to establish it theoretically and to compare with an experiment previously conducted. The analyses shown in this research indicate that the aspects of acoustic streaming generated by the four vibrators in the vessel can be correctly predicted and provide a foundation for the development of using this method for the enhancement of heat transfer.

  9. Convergence of intense aerial acoustic waves radiated by a rectangular transverse vibrating plate

    Nakai, Tomoki; Asami, Takuya; Miura, Hikaru

    2016-07-01

    A stripe-mode rectangular transverse vibrating plate can be used as a sound source that emits intense ultrasonic waves in air by placing a jut driving point outside the vibrating plate. The aim of this research was to use this vibrating plate to focus sound waves in the direction perpendicular to the nodal lines of the vibrating plate, which differs from the conventional direction. In this study, we investigated new methods for focusing the emitted sound waves by arranging reflective plates around the vibrating plate, using a design equation for each node between nodes in the vibrating plate, and placing additional reflective plates at an outer position beyond the convergence point, and found that a powerful acoustic field can be formed at an arbitrary position.

  10. Effect of the free surface and the rigid plane on structural vibration and acoustic radiation

    ZOU Yuanjie; ZHAO Deyou; LI Sheng

    2004-01-01

    The coupled fluid-structure interaction equation is established for bodies in the haft-space fluid domain, especially sitting on the infinite plane, based on the BEM (Boundary Element Method) theory. Then, the natural frequencies, vibration responses and the acoustic radiation for a box are calculated, and the effect of the free surface and the rigid plane is discussed. Finally, several relative factors including the plate thickness, the structure damping and the distance between the body and the infinite plane are studied. The results show that the effect of the free surface and the rigid plane on the structural natural frequencies, vibration responses and the acoustic radiation cannot be ignored.

  11. Ice induced vibrations of offshore structures

    E.A. Salganik

    2014-06-01

    Full Text Available The aim of the article was to analyze the process of the dynamic interaction between ice and offshore structures and find conditions of vibration beginnings. The problems of creating a full-scale finite element model of ice and offshore structure interaction and comparison of the received results of vibration conditions with the field data were solved. Modeling was realized with the finite element analysis software ANSYS. The problems of modeling cracks formation, checking the multilateral model using basic ice strength tests and finding ice loads level on different types of structures were solved in order to create a destructible ice model. The object of the investigation is the role of elastic and inertial offshore structure parameters and geometrical and dynamical ice field parameters in the process of ice-induced structure vibrations. Molikpaq drilling and oil production platform in Canada and Norströmsgrund lighthouse in Sweden were chosen as objects for modeling. The research contains verification of the results, their comparison to field data, load magnitudes from ISO 19906 «Petroleum and natural gas industries – Arctic offshore structures» algorithm and results of discrete element modeling. The results are acceptable in comparison with the results of other ice-induced vibration research.

  12. Flow-induced vibration analysis of nuclear components

    Excessive flow-induced vibration may lead to fretting-wear or fatigue problems in nuclear components. Some recent vibration problems and their solution are reviewed. The analytical and experimental techniques used to solve or preferably avoid flow-induced vibration problems are emphasized in this paper. Vibration excitation mechanisms in parallel and cross-flow and in both liquid and two-phase steam-water flow will be discussed. These vibration excitation mechanisms and the structural dynamics of nuclear components are formulated in analytical models. This is illustrated by the application of a computer model to analyse steam generator designs. Current studies related to flow-induced vibration are reviewed. Among these are: 1) the in-reactor vibration behaviour of nuclear fuel elements, 2) the prediction of vibration-fretting damage for heat exchanger tube materials and 3) the damping of wind-induced vibration of heavy water plant structures. (author)

  13. Fatigue failure by flow-induced vibration

    The mechanism of fatigue failure by flow-induced vibration was studied by using a newly developed small wind tunnel. The necessary conditions of flow-induced vibration for a carbon steel specimen attached to a larger styrofoam cylinder were first investigated. Possible methods to detect indications of fatigue crack initiation and propagation were sought. A fatigue life prediction method was also developed. The change in natural frequency and amplitude of the test cylinder and strain history at the prospective crack initiation sites were measured. The 0.45 C steel specimen contained an artificial small hole which is expected to become the crack initiation site. A small portable service strain histogram recorder (Mini Rainflow Corder, MRC) developed in another project was used to monitor the variation of strains due to crack growth from the small hole. Fatigue damage accumulation based on Miner's rule was calculated and compared with the experimental results. (author)

  14. Experimental investigations on flow induced vibration of an externally excited flexible plate

    Purohit, Ashish; Darpe, Ashish K.; Singh, S. P.

    2016-06-01

    Flow-induced vibration of a harmonically actuated flexible plate in the wake of an upstream bluff body is experimentally investigated. The experiments are performed in an open-ended wind tunnel. A flexible plate trailing a bluff body is under fluid induced excitation due to the flowing fluid. The additional external excitation to the trailing plate is applied using an electro-magnetic exciter. The frequency and amplitude of the external harmonic excitation are selected as variable parameters in the experiments and their effect on the plate vibration and is investigated. To know the nature of acoustic pressure wave generated from the vibrating system, near-field acoustic pressure is also measured. A laser vibrometer, a pressure microphone and a high-speed camera are employed to measure the plate vibration, pressure signal, and instantaneous images of the plate motion respectively. The results obtained indicate that the dynamics of the plate is influenced by both the flow-induced excitation and external harmonic excitation. When frequency of the two excitations is close enough, a large vibration level and a high tonal sound pressure are observed. At higher amplitude of external excitation, the frequency component corresponding to the flow-induced excitation is found to reduce significantly in the frequency spectrum of the vibration signal. It is observed that, for certain range of excitation frequency, the plate vibration first reduces, reaches a minimum value and then increases with increase in the level of external excitation. A fair qualitative agreement of the experimental results with numerical simulation result of the past study has been noted. In addition to the experiments, the role of phase difference between the flow-induced excitation generated from the front obstacle and externally applied harmonic excitation is investigated through numerical simulations. The result obtained reveals that the final steady state vibration of the coupled system is

  15. Vibration Damping Via Acoustic Treatment Attached To Vehicle Body Panels

    Gambino, Carlo

    Currently, in the automotive industry, the control of noise and vibration is the subject of much research, oriented towards the creation of innovative solutions to improve the comfort of the vehicle and to reduce its cost and weight. This thesis fits into this particular framework, as it aims to investigate the possibility of integrating the functions of sound absorptioninsulation and vibration damping in a unique component. At present the bituminous viscoelastic treatments, which are bonded to the car body panels, take charge of the vibration damping, while the sound absorption and insulation is obtained by means of the poroacoustic treatments. The solution proposed here consists of employing porous materials to perform both these functions, thus allowing the partial or complete removal of the viscoelastic damping treatments from the car body. This should decrease the weight of the vehicle, reducing fuel consumption and emissions, and it might also benefit production costs.

  16. Vibration amplitude and induced temperature limitation of high power air-borne ultrasonic transducers.

    Saffar, Saber; Abdullah, Amir

    2014-01-01

    The acoustic impedances of matching layers, their internal loss and vibration amplitude are the most important and influential parameters in the performance of high power airborne ultrasonic transducers. In this paper, the optimum acoustic impedances of the transducer matching layers were determined by using a genetic algorithm, the powerful tool for optimizating domain. The analytical results showed that the vibration amplitude increases significantly for low acoustic impedance matching layers. This enhancement is maximum and approximately 200 times higher for the last matching layer where it has the same interface with the air than the vibration amplitude of the source, lead zirconate titanate-pizo electric while transferring the 1 kW is desirable. This large amplitude increases both mechanical failure and temperature of the matching layers due to the internal loss of the matching layers. It has analytically shown that the temperature in last matching layer with having the maximum vibration amplitude is high enough to melt or burn the matching layers. To verify suggested approach, the effect of the amplitude of vibration on the induced temperature has been investigated experimentally. The experimental results displayed good agreement with the theoretical predictions. PMID:23664304

  17. The Harmonic Response Analysis with Acoustic-vibration Coupling of the Combustion Chamber under Different Combustion Conditions

    Zheng Min

    2016-01-01

    Full Text Available In this paper, numerical calculations of harmonic response with acoustic-vibration coupling of the combustion chamber under different combustion conditions has been performed by combining CFD and FEM methods. Temperature and sound pressure fields created by the flame in the combustion chamber are calculated first. And then the results of the CFD are exported to the FEM analysis for the interaction between acoustic waves and wall vibrations. The possible acoustic-vibration coupled eigenfrequencies at given combustion conditions are predicted by the harmonic response analysis.

  18. VIBRATION AND ACOUSTIC RADIATION FROM SUBMERGED STIFFENED SPHERICAL SHELL WITH DECK-TYPE INTERNAL PLATE

    ChenJnnming; HuangYuying

    2003-01-01

    Based on the motion differential equations of vibration and acoustic coupling system for thin elastic spherical shell with an elastic plate attached to its internal surface, in which Dirac-δ functions are employed to introduce the moments and forces applied by the attachment on the surface of shell, by means of expanding field quantities as Legendre series, a semi-analytic solution is derived for the vibration and acoustic radiation from a submerged stiffened spherical shell with a deck-type internal plate, which has a satisfactory computational effectiveness and precision for an arbitrary frequency range. It is easy to analyze the effect of the internal plate on the acoustic radiation field by using the formulas obtained by the method proposed. It is concluded that the internal plate can significantly change the mechanical and acoustic characteristics of shell, and give the coupling system a very rich resonance frequency spectrum. Moreover, the method can be used to study the acoustic radiation mechanism in similar structures as the one studied here.

  19. Pedestrian-induced lateral vibrations of footbridges

    Ingólfsson, Einar Thór

    experimental campaign involved 71 test subjects who covered approximately 55 km of walking distributed on almost 5000 individual tests. An in-depth analysis of the movement of the pedestrians that participated in the experimental campaign reveal that synchronisation is not a pre-condition for the ix...... statistically reliable analytical tool for modelling of pedestrian-induced lateral vibrations. It is shown that the modal response of a footbridge subject to a pedestrian crowd is sensitive to the selection of the pacing rate distribution within the group, the magnitude of ambient loads and the total duration...

  20. Separation of the vibration-induced signal of oil debris for vibration monitoring

    Oil debris sensors are designed for monitoring machine component conditions by detecting oil debris in the circulating oil lines. However, these sensors are not only sensitive to metallic particles, but are susceptible to machinery vibration as well. The vibration-induced signal has thus far been treated as interference and is accordingly removed to better reveal the particle signature. As the vibration signal also contains important information on machine health, which can be used to detect not only the machine component faults but also machine structural malfunctions, we propose a joint integral and wavelet transform approach to separate the vibration and particle signals to make the oil debris sensor multi-functional. The recovered vibration signal is then used to detect faults that cannot be revealed by examining oil debris content. Our experimental results have shown that the separated vibration signal is, in general, consistent with the vibration velocity and hence can be used as an auxiliary vibration monitoring tool

  1. Flow induced vibration of an airfoil with three degrees of freedom

    Růžička, M.; Feistauer, M.; Horáček, Jaromír; Sváček, Petr

    Praha : Institute of Thermomechanics, Academy of Sciences of the Czech Republic, v. v. i., 2008 - (Zolotarev, I.; Horáček, J.), s. 507-512 ISBN 80-87012-12-7. [International Conference on Flow Induced Vibration /9./ FIV2008. Praha (CZ), 30.06.2008-03.07.2008] R&D Projects: GA AV ČR IAA200760613 Institutional research plan: CEZ:AV0Z20760514 Keywords : aeroelasticity * flutter * finite element method Subject RIV: BI - Acoustics

  2. COMPLEX HEAT TRANSFER ENHANCEMENT BY FLUID INDUCED VIBRATION

    2003-01-01

    A new method of heat transfer enhancement by fluid induced vibration was put forward, and its theoretical analysis and experimental study were performed. Though people always try to prophylaxis fluid induced vibration for regarding it as an accident, the utilization space of fluid induced vibration is still very large. The in-surface and out-surface vibrations which come from the fluid induce elastic tube bundles, can effectively increase the convective heat transfer coefficient, and also decrease the fouling resistance, then increase the heat transfer coefficient remarkably.

  3. Vibrational and acoustical characteristics of the piano soundboard

    Ege, Kerem

    2012-01-01

    The vibrations of the soundboard of an upright piano in playing condition are investigated. It is first shown that the linear part of the response is at least 50 dB above its nonlinear component at normal levels of vibration. Given this essentially linear response, a modal identification is performed in the mid-frequency domain [300-2500] Hz by means of a novel high resolution modal analysis technique (Ege, Boutillon and David, JSV, 2009). The modal density of the spruce board varies between 0.05 and 0.01 modes/Hz and the mean loss factor is found to be approximately 2%. Below 1.1 kHz, the modal density is very close to that of a homogeneous isotropic plate with clamped boundary conditions. Higher in frequency, the soundboard behaves as a set of waveguides defined by the ribs. A numerical determination of the modal shapes by a finite-element method confirms that the waves are localised between the ribs. The dispersion law in the plate above 1.1 kHz is derived from a simple waveguide model. We present how the ...

  4. Gearbox Tooth Cut Fault Diagnostics Using Acoustic Emission and Vibration Sensors — A Comparative Study

    Yongzhi Qu

    2014-01-01

    Full Text Available In recent years, acoustic emission (AE sensors and AE-based techniques have been developed and tested for gearbox fault diagnosis. In general, AE-based techniques require much higher sampling rates than vibration analysis-based techniques for gearbox fault diagnosis. Therefore, it is questionable whether an AE-based technique would give a better or at least the same performance as the vibration analysis-based techniques using the same sampling rate. To answer the question, this paper presents a comparative study for gearbox tooth damage level diagnostics using AE and vibration measurements, the first known attempt to compare the gearbox fault diagnostic performance of AE- and vibration analysis-based approaches using the same sampling rate. Partial tooth cut faults are seeded in a gearbox test rig and experimentally tested in a laboratory. Results have shown that the AE-based approach has the potential to differentiate gear tooth damage levels in comparison with the vibration-based approach. While vibration signals are easily affected by mechanical resonance, the AE signals show more stable performance.

  5. Water Induced Vibration in the NSRRC

    Wang, Duan J; Tsai, Zong-Da; Wang, Jeremy

    2005-01-01

    Water flow related vibrations were found on the spectrum of electron beam position monitor in the NSRRC. They were associated with the vibrations of quadrupole magnets. One major vibration source was from a pump in the cooling water system. Most amount of vibration coupled through water pipe and water flow and propagated to the magnets. A small water flow station was set up to study the effect about coupling, propagating and excitation. Some damping schemes tested in the ring to improve the vibration are also included..

  6. Vibration Control Induced by Ice of a Jacket Platform

    郑宏宇; 姜大宁; 唐友刚; 周满红

    2003-01-01

    Based on the self-excited vibration theory of ice, the vibration control technology of jacket platform is studied in this paper. The magnetorheological suspensions (MR) unit is chosen as the damper, the control objective function for vibration excited by ice is determined by instantaneous optimal control (IOC) method, and genetic algorithm (GA) is used to select the optimal control force. For the jacket platform of 40 m in height and a 3-floor deck, the vibration responses induced by ice have been calculated before and after control considering the different thickness and speed of ice. It is shown that the control method presented in this paper can reduce the vibration response by 30%, and it is feasible to adopt MR absorber and GA in the control of vibration induced by ice.

  7. Identification of vibration excitations from acoustic measurements using near field acoustic holography and the force analysis technique

    Pézerat, C.; Leclère, Q.; Totaro, N.; Pachebat, M.

    2009-10-01

    This study presents a method of using acoustic holography and the force analysis technique to identify vibration sources from radiated noise measurements. The structure studied is a plate excited by a shaker on which three measurements were performed: the first is a reference measurement of plate velocity obtained by scanning laser vibrometry, the second is based on sound pressure measurements in the near field of the structure, and the third is the measurement of normal acoustic velocities by using a p-U probe recently developed by Microflown Technologies. This was followed by the application of classical NAH, known as pressure-to-velocity holography and velocity-to-velocity holography to predict the plate velocity field from acoustic measurements at distances of 1 and 5 cm. Afterwards, the force analysis technique, also known as the RIFF technique, is applied with these five data sets. The principle is to inject the displacement field of the structure into its equation of motion and extract the resulting force distribution. This technique requires regularization done by a low-pass filter in the wavenumber domain. Apart from pressure-to-velocity holography at 5 cm, the reconstructed force distribution allows localizing the excitation point in the measurement area. FAT regularization is also shown to improve results as its cutoff wavenumber is optimized with the natural wavenumber of the plate. Lastly, quantitative force values are extracted from force distributions at all frequencies of the band 0-4 kHz studied and compared with the force spectrum measured directly by a piezoelectric sensor.

  8. On the interaction of a vibrating plate with an acoustic medium

    Mixson, J. S.; Koval, L. R.

    1974-01-01

    The interaction of a vibrating plate with an adjacent acoustic medium is important in problems involving the radiation of sound from panels, in problems involving the transmission of sound through walls of buildings, aircraft, or launch vehicles; and in problems involving the estimation of damping and the stress amplitude of vibration for panel-fatigue predictions. There appear to have been no systematic studies of the effects on the plate of fluid coupling for an arbitrary fluid-mass/plate-mass loading ratio. An attempt is made to determine this effect for a wide range of fluid-plate mass ratios without resorting to the usual simplifications of light or heavy fluid loading. Emphasis is with the plate motion rather than the radiation of sound.

  9. SPEED DEPENDENCE OF ACOUSTIC VIBRATION PROPAGATION FROM THE FERRITIC GRAIN SIZE IN LOW-CARBON STEEL

    I. A. Vakulenko

    2015-08-01

    Full Text Available Purpose. It is determining the nature of the ferrite grain size influence of low-carbon alloy steel on the speed propagation of acoustic vibrations. Methodology. The material for the research served a steel sheet of thickness 1.4 mm. Steel type H18T1 had a content of chemical elements within grade composition: 0, 12 % C, 17, 5 % Cr, 1 % Mn, 1, 1 % Ni, 0, 85 % Si, 0, 9 % Ti. The specified steel belongs to the semiferritic class of the accepted classification. The structural state of the metal for the study was obtained by cold plastic deformation by rolling at a reduction in the size range of 20-30 % and subsequent recrystallization annealing at 740 – 750 ° C. Different degrees of cold plastic deformation was obtained by pre-selection of the initial strip thickness so that after a desired amount of rolling reduction receives the same final thickness. The microstructure was observed under a light microscope, the ferrite grain size was determined using a quantitative metallographic technique. The using of X-ray structural analysis techniques allowed determining the level of second-order distortion of the crystal latitude of the ferrite. The speed propagation of acoustic vibrations was measured using a special device such as an ISP-12 with a working frequency of pulses 1.024 kHz. As the characteristic of strength used the hardness was evaluated by the Brinell’s method. Findings. With increasing of ferrite grain size the hardness of the steel is reduced. In the case of constant structural state of metal, reducing the size of the ferrite grains is accompanied by a natural increasing of the phase distortion. The dependence of the speed propagation of acoustic vibrations up and down the rolling direction of the ferrite grain size remained unchanged and reports directly proportional correlation. Originality. On the basis of studies to determine the direct impact of the proportional nature of the ferrite grain size on the rate of propagation of sound

  10. Flow-induced vibrations of a rotating cylinder

    Bourguet, Rémi; Lo Jacono, David

    2014-01-01

    International audience The flow-induced vibrations of a circular cylinder, free to oscillate in the cross-flow direction and subjected to a forced rotation about its axis, are analysed by means of two- and three-dimensional numerical simulations. The impact of the symmetry breaking caused by the forced rotation on the vortex-induced vibration (VIV) mechanisms is investigated for a Reynolds number equal to 100, based on the cylinder diameter and inflow velocity. The cylinder is found to osc...

  11. Acoustically induced transparency using Fano resonant periodic arrays

    Amin, M.

    2015-10-22

    A three-dimensional acoustic device, which supports Fano resonance and induced transparency in its response to an incident sound wave, is designed and fabricated. These effects are generated from the destructive interference of closely coupled one broad- and one narrow-band acoustic modes. The proposed design ensures excitation and interference of two spectrally close modes by locating a small pipe inside a wider and longer one. Indeed, numerical simulations and experiments demonstrate that this simple-to-fabricate structure can be used to generate Fano resonance as well as acoustically induced transparency with promising applications in sensing, cloaking, and imaging.

  12. Acoustically induced transparency using Fano resonant periodic arrays

    Amin, M.; Elayouch, A.; Farhat, M.; Addouche, M.; Khelif, A.; Baǧcı, H.

    2015-10-01

    A three-dimensional acoustic device, which supports Fano resonance and induced transparency in its response to an incident sound wave, is designed and fabricated. These effects are generated from the destructive interference of closely coupled one broad- and one narrow-band acoustic modes. The proposed design ensures excitation and interference of two spectrally close modes by locating a small pipe inside a wider and longer one. Indeed, numerical simulations and experiments demonstrate that this simple-to-fabricate structure can be used to generate Fano resonance as well as acoustically induced transparency with promising applications in sensing, cloaking, and imaging.

  13. Flow-induced vibration -- 1994. PVP-Volume 273

    Flow-induced vibration is a subject of practical interest to many engineering disciplines, including the power generation, process, and petrochemical industries. In the nuclear industry, flow-induced vibration reaches a higher level of concern because of safety issues and the huge cost associated with down time and site repair. Not surprisingly, during the last 25 years a tremendous amount of effort has been spent in the study of flow-induced vibration phenomena related to nuclear plant components, notably nuclear steam generator tube banks and nuclear fuel bundles. Yet, in spite of this concentrated effort, the industry is still not free from flow-induced vibration-related problems. This explains why in this volume almost half of the papers address the issue of cross-flow induced vibration in tube bundles, with applications to the nuclear steam generator and nuclear fuel bundles in mind. Unlike 10 or 15 years ago, when flow-induced vibration studies almost always involved experimentation and empirical studies, the advent of high-speed computers has enabled numerical calculation and simulation of this complex phenomenon to take place. Separate abstracts were prepared for 27 papers in this volume

  14. A new acoustic portal into the odontocete ear and vibrational analysis of the tympanoperiotic complex.

    Ted W Cranford

    Full Text Available Global concern over the possible deleterious effects of noise on marine organisms was catalyzed when toothed whales stranded and died in the presence of high intensity sound. The lack of knowledge about mechanisms of hearing in toothed whales prompted our group to study the anatomy and build a finite element model to simulate sound reception in odontocetes. The primary auditory pathway in toothed whales is an evolutionary novelty, compensating for the impedance mismatch experienced by whale ancestors as they moved from hearing in air to hearing in water. The mechanism by which high-frequency vibrations pass from the low density fats of the lower jaw into the dense bones of the auditory apparatus is a key to understanding odontocete hearing. Here we identify a new acoustic portal into the ear complex, the tympanoperiotic complex (TPC and a plausible mechanism by which sound is transduced into the bony components. We reveal the intact anatomic geometry using CT scanning, and test functional preconceptions using finite element modeling and vibrational analysis. We show that the mandibular fat bodies bifurcate posteriorly, attaching to the TPC in two distinct locations. The smaller branch is an inconspicuous, previously undescribed channel, a cone-shaped fat body that fits into a thin-walled bony funnel just anterior to the sigmoid process of the TPC. The TPC also contains regions of thin translucent bone that define zones of differential flexibility, enabling the TPC to bend in response to sound pressure, thus providing a mechanism for vibrations to pass through the ossicular chain. The techniques used to discover the new acoustic portal in toothed whales, provide a means to decipher auditory filtering, beam formation, impedance matching, and transduction. These tools can also be used to address concerns about the potential deleterious effects of high-intensity sound in a broad spectrum of marine organisms, from whales to fish.

  15. Vibration induced flow in hoppers: DEM 2D polygon model

    2008-01-01

    A two-dimensional discrete element model (DEM) simulation of cohesive polygonal particles has been developed to assess the benefit of point source vibration to induce flow in wedge-shaped hoppers. The particle-particle interaction model used is based on a multi-contact principle.The first part of the study investigated particle discharge under gravity without vibration to determine the critical orifice size (Be) to just sustain flow as a function of particle shape. It is shown that polygonal-shaped particles need a larger orifice than circular particles. It is also shown that Be decreases as the number of particle vertices increases. Addition of circular particles promotes flow of polygons in a linear manner.The second part of the study showed that vibration could enhance flow, effectively reducing Be. The model demonstrated the importance of vibrator location (height), consistent with previous continuum model results, and vibration amplitude in enhancing flow.

  16. Experimental and numerical prediction of railway induced vibration

    Hans VERBRAKEN; Geert LOMBAERT; Geert DEGRANDE

    2012-01-01

    In this paper,both measurements and numerical simulations of railway induced vibration are discussed.A measurement campaign has been carried out along the high-speed railway track in Lincent,Belgium.The experimental determination of transfer functions and vibration velocity during train passages are discussed.A numerical model is introduced to predict the transfer functions and the vibration velocity during train passages.The comparison of experimental and numerical results demonstrates the importance of accurate numerical models and input data.The results are obtained in the framework of the development of a hybrid prediction method,where numerical and experimental data can be combined to improve the prediction accuracy for railway induced vibration.

  17. Reduction of Train-induced Vibrations by using Barriers

    Giovanni Leonardi

    2014-05-01

    Full Text Available The problem of the ground-borne vibration caused by high speed trains has received considerable attention in recent years, due to the effects of vibration on buildings, in terms of physical damage and on population, in terms of discomfort. The problem has become more significant with the increase of speed and weight of trains, which results in heavier loads on the tracks. Therefore, there is the necessity to find a method, which allows investigating the propagation of vibration waves in the soil. This study aims to study the train-induced ground vibration and the mitigation effects of barriers using a Finite Element Method (FEM model. Two different types of barriers were evaluated considering their stiffness and a benchmark model without mitigation measures was also analyzed to evaluate the effectiveness of the considered barriers. The results of the proposed elaborations have been finalized to the assessment of the incidence of the barrier on the vibration state induced from the passage of a high speed trains and the following conclusions can be made: concrete seems to provide a significative reduction of the vibration. The proposed method can be successfully applied to a preliminary analysis of the influence of different types of barriers on the dynamic properties of vibration waves in the soil.

  18. Attenuation of cryocooler induced vibration in spaceborne infrared payloads

    Veprik, A.; Twitto, A.

    2014-01-01

    Recent advancement of operational responsive space programs calls for a development of compact, reliable, low power and vibration free cryogenic cooling for sophisticated infrared payloads. The refrigeration in a typical closed cycle split Stirling linear cryocooler is achieved by a cyclic compression and expansion of a gaseous working agent due to a synchronized reciprocation of electro-dynamically and pneumatically actuated compressor and expander pistons. Attenuation of the cryocooler induced vibration usually relies on the concept of actively assisted momentum cancellation. In a typical dual-piston compressor this objective is achieved by actively synchronizing the motion of oppositely moving piston assemblies; a typical single-piston expander may be counterbalanced by a motorized counter-balancer. The above approach produces complexity, weight, size, high incurred costs and affects reliability. The authors analyze the case of passive attenuation the vibration export induced by the split Stirling linear cryocooler comprised of inline mounted single-piston compressor and expander. Placement of all the moving components onto a common axis results in a single axis consolidation of vibration export and enables use of single tuned dynamic absorber and low frequency vibration mount. From theoretical analysis and full-scale testing, the performance of such vibration protection arrangement is similar to known systems of active vibration cancellation.

  19. Vibration-Induced Conductance Fluctuation (VICOF) Testing of Soils

    Kish, L B; Kishne, A S; Kish, Laszlo B.; Morgan, Cristine L.S.; Kishne, Andrea Sz.

    2005-01-01

    In this Letter, we propose and experimentally demonstrate a simple method to provide additional information by conductance measurements of soils. While the AC electrical conductance of the soil is measured, it is exposed to a periodic vibration. The vibration-induced density fluctuation implies a corresponding conductivity fluctuation that can be seen as combination frequency components, the sum and the difference of the mean AC frequency and the vibration frequency, in the current response. The method is demonstrated by measurements on two different soil types.

  20. General theory of detection of signal induced in vibrating magnetometer

    Assuming the point dipole approximation only and making use of the vectorial notation, signal (EMF) induced in a single-turn pick-up coil of the vibrating magnetometer are calculated for the case of any orientation of the coil, of vibration axis and of the magnetic moment of the sample. On the basis of formula obtained, three types of measurement geometries have been distinquished and for these the qualitative analysis is made. (author)

  1. Modelling flow-induced vibrations of gates in hydraulic structures

    Erdbrink, C.D.

    2014-01-01

    The dynamic behaviour of gates in hydraulic structures caused by passing flow poses a potential threat to flood protection. Complex interactions between the turbulent flow and the suspended gate body may induce undesired vibrations. This thesis contributes to a better understanding and prevention of gate vibrations by employing a variety of computational approaches. Simulations with the finite-element method are used to analyse the fluid-structure interaction of a new underflow gate type whic...

  2. Circus, software for computation of flow induced vibrations in piping system. General purpose

    This paper is a presentation of the code CIRCUS version 2. CIRCUS deals with the hydraulic, acoustic and vibratory behaviour of piping systems under acoustic loads. CIRCUS first computes permanent mean-flow, and associated acoustic loads. It then determines the acoustic and vibration response along the piping system. The CIRCUS software is used at EDF to check the design of piping system and to investigate solutions in case of damage or troubleshooting. (author)

  3. Flow-induced vibration study in the LOFT steam generator

    Carmichael, C.F.

    1977-10-18

    The consequences of flow induced vibration in the LOFT steam generator were studied. Tube-baffle contact and fretting wear are expected to occur while tube-tube contact is not predicted. The LOFT steam generator is, in all probability adequate from a fluid induced viewpoint for the scheduled service of the LOFT facility at power. 37 refs., 5 figs., 3 tabs.

  4. Vibration optimization of ZnO thin film bulk acoustic resonator with ring electrodes

    Zhao, Zinan; Qian, Zhenghua; Wang, Bin

    2016-04-01

    A rectangular ZnO thin film bulk acoustic resonator with ring electrodes is presented in this paper to demonstrate the existence of a nearly uniform displacement distribution at the central part of this typical resonator. The variational formulation based on two-dimensional scalar differential equations provides a theoretical foundation for the Ritz method adopted in our analysis. The resonant frequencies and vibration distributions for the thickness-extensional modes of this ring electrode resonator are obtained. The structural parameters are optimized to achieve a more uniform displacement distribution and therefore a uniform mass sensitivity, which guarantee the high accuracy and repeatable measurement for sensor detection in an air or a liquid environment. These results provide a fundamental reference for the design and optimization of the high quality sensor.

  5. Nanoparticle monolayer-based flexible strain gauge with ultrafast dynamic response for acoustic vibration detection

    Lizhi Yi[1; Weihong Jiao[1; Ke Wu[1; Lihua Qian[1; Xunxing Yu[2; Qi Xia[2; Kuanmin Mao[2; Songliu Yuan[1; Shuai Wang[3; Yingtao Jiang[4

    2015-01-01

    The relatively poor dynamic response of current flexible strain gauges has prevented their wide adoption in portable electronics. In this work, we present a greatly improved flexible strain gauge, where one strip of Au nanoparticle (NP) monolayer assembled on a polyethylene terephthalate film is utilized as the active unit. The proposed flexible gauge is capable of responding to applied stimuli without detectable hysteresis via electron tunneling between adjacent nanoparticles within the Au NP monolayer. Based on experimental quantification of the time and frequency domain dependence of the electrical resistance of the proposed strain gauge, acoustic vibrations in the frequency range of 1 to 20,000 Hz could be reliably detected. In addition to being used to measure musical tone, audible speech, and creature vocalization, as demonstrated in this study, the ultrafast dynamic response of this flexible strain gauge can be used in a wide range of applications, including miniaturized vibratory sensors, safe entrance guard management systems, and ultrasensitive pressure sensors.

  6. Similarity analysis and prediction for data of structural acoustic and vibration

    Support vector machine (SVM) is a learning machine based on statistical learning theory, which can get a model having good generalization. It can solve 'learning more' when dealing with small size. It can also avoid 'dimensional disaster' when solving nonlinear problems. This paper works on the parameters optimization for support vector regression machine (SVRM) and its applications. Solution path algorithm can save much CPU time when it is employed to optimize the regularization parameter of SVRM. Simulated annealing algorithm has good ability of finding global optimal solution. An improved solution path algorithm and simulated annealing algorithm are combined to optimize parameters of SVRM in the regression analysis of the acoustic and vibration data for complex practical problems. The numerical results show the model has good predictive capability. (authors)

  7. Applications of Lorentz force in medical acoustics: Lorentz force hydrophone, Lorentz Force Electrical Impedance Tomography, Imaging of shear waves induced by Lorentz force

    Grasland-Mongrain, Pol

    2014-01-01

    The ability of the Lorentz force to link a mechanical displacement to an electrical current presents a strong interest for medical acoustics, and three applications were studied in this thesis. In the first part of this work, a hydrophone was developed for mapping the particle velocity of an acoustic field. This hydrophone was constructed using a thin copper wire and an external magnetic field. A model was elaborated to determine the relationship between the acoustic pressure and the measured electrical current, which is induced by Lorentz force when the wire vibrates in the acoustic field of an ultrasound transducer. The built prototype was characterized and its spatial resolution, frequency response, sensitivity, robustness and directivity response were investigated. An imaging method called Lorentz Force Electrical Impedance Tomography was also studied. In this method, a biological tissue is vibrated by ultrasound in a magnetic field, which induces an electrical current by Lorentz force. The electrical imp...

  8. Numerical Research about Influence of Blade Outlet Angle on Flow-Induced Noise and Vibration for Centrifugal Pump

    Ailing Yang; Dapeng Lang; Guoping Li; Eryun Chen; Ren Dai

    2014-01-01

    A hybrid numerical method was used to calculate the flow-induced noise and vibration of the centrifugal pump in the paper. The unsteady flows inside the centrifugal pumps with different blade outlet angles were simulated firstly. The unsteady pressure on the inner surface of the volute and the unsteady force applied on the impeller were analyzed. Then the vibration of the volute and sound field were calculated based on an acoustic-vibro-coupling method. The results show that the pump head has...

  9. Hydrodynamics induced vibration to trash-racks

    In conventional power plants trash-racks are provided at the intakes to protect the turbines. In pumped storage plants, the draft tube or tailrace must also have trash-racks to protect the units while pumping. Because the loads believed to cause many failures of trash-racks are dynamic in nature, it is important to understand the dynamic characteristics of trash-racks structures in general and a single rack in particular. The classical added-mass solution structure-fluid dynamic interaction is known as an approximate solution procedure. An accurate added-mass approach mixed with implementation in finite element framework is proposed. In this proposal, experimental conclusions, supported by theory, led to presentation of more accurate results in vibration of trash-racks. This numerical solution as a powerful method to solve such a complex problem can be employed to carry out dynamic characteristics of these structures while vibrating in water

  10. Scale modeling flow-induced vibrations of reactor components

    Similitude relationships currently employed in the design of flow-induced vibration scale-model tests of nuclear reactor components are reviewed. Emphasis is given to understanding the origins of the similitude parameters as a basis for discussion of the inevitable distortions which occur in design verification testing of entire reactor systems and in feature testing of individual component designs for the existence of detrimental flow-induced vibration mechanisms. Distortions of similitude parameters made in current test practice are enumerated and selected example tests are described. Also, limitations in the use of specific distortions in model designs are evaluated based on the current understanding of flow-induced vibration mechanisms and structural response

  11. Implementing wavelet packet transform for valve failure detection using vibration and acoustic emission signals

    The efficiency of reciprocating compressors relies heavily on the health condition of its moving components, most importantly its valves. Previous studies showed good correlation between the dynamic response and the physical condition of the valves. These can be achieved by employing vibration technique which is capable of monitoring the response of the valve, and acoustic emission technique which is capable of detecting the valves' material deformation. However, the relationship/comparison between the two techniques is rarely investigated. In this paper, the two techniques were examined using time-frequency analysis. Wavelet packet transform (WPT) was chosen as the multi-resolution analysis technique over continuous wavelet transform (CWT), and discrete wavelet transform (DWT). This is because WPT could overcome the high computational time and high redundancy problem in CWT and could provide detailed analysis of the high frequency components compared to DWT. The features of both signals can be extracted by evaluating the normalised WPT coefficients for different time window under different valve conditions. By comparing the normalised coefficients over a certain time frame and frequency range, the feature vectors revealing the condition of valves can be constructed. One way analysis of variance was employed on these feature vectors to test the significance of data under different valve conditions. It is believed that AE signals can give a better representation of the valve condition as it can detect both the fluid motion and material deformation of valves as compared to the vibration signals.

  12. Implementing wavelet packet transform for valve failure detection using vibration and acoustic emission signals

    Sim, H. Y.; Ramli, R.; Abdullah, M. A. K.

    2012-05-01

    The efficiency of reciprocating compressors relies heavily on the health condition of its moving components, most importantly its valves. Previous studies showed good correlation between the dynamic response and the physical condition of the valves. These can be achieved by employing vibration technique which is capable of monitoring the response of the valve, and acoustic emission technique which is capable of detecting the valves' material deformation. However, the relationship/comparison between the two techniques is rarely investigated. In this paper, the two techniques were examined using time-frequency analysis. Wavelet packet transform (WPT) was chosen as the multi-resolution analysis technique over continuous wavelet transform (CWT), and discrete wavelet transform (DWT). This is because WPT could overcome the high computational time and high redundancy problem in CWT and could provide detailed analysis of the high frequency components compared to DWT. The features of both signals can be extracted by evaluating the normalised WPT coefficients for different time window under different valve conditions. By comparing the normalised coefficients over a certain time frame and frequency range, the feature vectors revealing the condition of valves can be constructed. One way analysis of variance was employed on these feature vectors to test the significance of data under different valve conditions. It is believed that AE signals can give a better representation of the valve condition as it can detect both the fluid motion and material deformation of valves as compared to the vibration signals.

  13. Poiseuille flow-induced vibrations of two cylinders in tandem

    Lin, Jianzhong; Jiang, Renjie; Chen, Zhongli; Ku, Xiaoke

    2013-07-01

    Laminar flows past two tandem cylinders which are free to move transversely in a parallel-wall channel were studied numerically by the lattice Boltzmann method. With fixed Reynolds number Re=100, blockage ratio β=1/4 and structural damping ξ=0, the effect of streamwise separation between two cylinders at a range of S/D=[1.1, 10] on the motions of cylinders and fluids was studied for both mass ratios of m(*)=1 and m(*)=0.1. A variety of distinct vibration regimes involving periodic, quasi-periodic and non-periodic vibrations with corresponding flow patterns were observed. A detailed analysis of the vibration amplitudes, vibration frequencies and relative equilibrium positions for both mass ratios demonstrated that as S/D increases, the interaction of the two cylinders first enhances and then reduces. In the strong coupling regime, both cylinders oscillate periodically around the centerline of the channel with large vibration amplitudes and high vibration frequencies. By comparing with the case of an isolated cylinder, a further study indicated that the gap flow plays an important role in such a dynamic system, and the vortex cores formation behind the front cylinder causes the interaction of the cylinders decouple rapidly. Based on the present observations, such a dynamic model system can be considered as a novel type of vortex-induced vibrations (VIV) and is expected to find applications in fluid mixing and heat transfer.

  14. Test-Anchored Vibration Response Predictions for an Acoustically Energized Curved Orthogrid Panel with Mounted Components

    Frady, Gregory P.; Duvall, Lowery D.; Fulcher, Clay W. G.; Laverde, Bruce T.; Hunt, Ronald A.

    2011-01-01

    rich body of vibroacoustic test data was recently generated at Marshall Space Flight Center for component-loaded curved orthogrid panels typical of launch vehicle skin structures. The test data were used to anchor computational predictions of a variety of spatially distributed responses including acceleration, strain and component interface force. Transfer functions relating the responses to the input pressure field were generated from finite element based modal solutions and test-derived damping estimates. A diffuse acoustic field model was applied to correlate the measured input sound pressures across the energized panel. This application quantifies the ability to quickly and accurately predict a variety of responses to acoustically energized skin panels with mounted components. Favorable comparisons between the measured and predicted responses were established. The validated models were used to examine vibration response sensitivities to relevant modeling parameters such as pressure patch density, mesh density, weight of the mounted component and model form. Convergence metrics include spectral densities and cumulative root-mean squared (RMS) functions for acceleration, velocity, displacement, strain and interface force. Minimum frequencies for response convergence were established as well as recommendations for modeling techniques, particularly in the early stages of a component design when accurate structural vibration requirements are needed relatively quickly. The results were compared with long-established guidelines for modeling accuracy of component-loaded panels. A theoretical basis for the Response/Pressure Transfer Function (RPTF) approach provides insight into trends observed in the response predictions and confirmed in the test data. The software developed for the RPTF method allows easy replacement of the diffuse acoustic field with other pressure fields such as a turbulent boundary layer (TBL) model suitable for vehicle ascent. Structural responses

  15. Strategy for predicting railway-induced vibrations in buildings

    Persson, Peter; Persson, Kent; Andersen, Lars Vabbersgaard;

    2016-01-01

    Urban densification is a way of accommodating population growth. Land adjacent to railways is used for constructing residences and other buildings, and new tramway systems are planned. Under these circumstances, nearby buildings will be exposed to vibrations and noise that may become a nuisance for...... the residents. It is necessary, even at an early stage of planning, to assess the extent of the vibrations and state requirements for the building in order to avoid costly changes at later stages. Ground vibration induced by railway traffic is studied in the paper. The aim is to develop a strategy for...... typical buildings can be predicted. Design of building foundations and structural design can then be addressed. Field vibration measurements along railway tracks as well as at built-up areas have been carried out. Conclusions from the measurements and numerical simulation s are discussed to establish a...

  16. Flow-induced vibrations an engineering guide

    Naudascher, Eduard

    2012-01-01

    Despite their variety, the vibration phenomena from many different engineering fields can be classified into a relatively few basic excitation mechanisms. The classification enables engineers to identify all possible sources of excitation in a given system and to assess potential dangers. This graduate-level text presents a synthesis of research results and practical experience from disparate fields in the form of engineering guidelines. It is particularly geared toward assessing the possible sources of excitation in a flow system, in identifying the actual danger spots, and in finding appropr

  17. Failure Progress of 3D Reinforced GFRP Laminate during Static Bending, Evaluated by Means of Acoustic Emission and Vibrations Analysis

    Mateusz Koziol

    2015-12-01

    Full Text Available The work aimed to assess the failure progress in a glass fiber-reinforced polymer laminate with a 3D-woven and (as a comparison plain-woven reinforcement, during static bending, using acoustic emission signals. The innovative method of the separation of the signal coming from the fiber fracture and the one coming from the matrix fracture with the use of the acoustic event’s energy as a criterion was applied. The failure progress during static bending was alternatively analyzed by evaluation of the vibration signal. It gave a possibility to validate the results of the acoustic emission. Acoustic emission, as well as vibration signal analysis proved to be good and effective tools for the registration of failure effects in composite laminates. Vibration analysis is more complicated methodologically, yet it is more precise. The failure progress of the 3D laminate is “safer” and more beneficial than that of the plain-woven laminate. It exhibits less rapid load capacity drops and a higher fiber effort contribution at the moment of the main laminate failure.

  18. Low Head, Vortex Induced Vibrations River Energy Converter

    Bernitsas, Michael B.; Dritz, Tad

    2006-06-30

    Vortex Induced Vibrations Aquatic Clean Energy (VIVACE) is a novel, demonstrated approach to extracting energy from water currents. This invention is based on a phenomenon called Vortex Induced Vibrations (VIV), which was first observed by Leonardo da Vinci in 1504AD. He called it ‘Aeolian Tones.’ For decades, engineers have attempted to prevent this type of vibration from damaging structures, such as offshore platforms, nuclear fuel rods, cables, buildings, and bridges. The underlying concept of the VIVACE Converter is the following: Strengthen rather than spoil vortex shedding; enhance rather than suppress VIV; harness rather than mitigate VIV energy. By maximizing and utilizing this unique phenomenon, VIVACE takes this “problem” and successfully transforms it into a valuable resource for mankind.

  19. Evaluation of blast-induced vibration effects on structures 1

    Lee, Jong Rim; Jeon, Gyu Shick; Lee, Dae Soo; Joo, Kwang Ho; Lee, Woong Keon [Korea Electrotechnology Research Inst., Changwon (Korea, Republic of); Ryu, Chang Ha; Chung, So Keul; Lee, Kyung Won; Shin, Hee Soon; Chun, Sun Woo; Park, Yeon Jun; Synn, Joong Ho; Choi, Byung Hee [Korea Inst. of Geology Mining and Materials, Taejon (Korea, Republic of)

    1995-12-31

    Due to the difficulties of obtaining construction site for new plants, following ones are inevitably being built in the site adjacent to existing power plants. Therefore considerable thought has been recently given to the dynamic loading generated by blasting works near the plants to maintain the safety of structures and facilities in power plants. Our own standard for safety level of blast vibration is not prepared yet, and foreign standards have been generally employed without theoretical and experimental verification. Safety-related structures of power plants and facilities have to be protected against the effects of possible hazards due to blast vibration. Earthquakes have been considered a major dynamic design loading as a requirement of plant design, but the effects of blast-induced vibration are not. In order to ensure the safety, rational safe criterion should be established and blast design should be satisfy it, which requires the development of a model for prediction of vibration level through more systematic measurement and analysis. The main objectives of the study are : to provide background data for establishing the rational safe vibration limits, to develop models for prediction of blast vibration level, to establish safe blast design criterion, and to accumulate techniques for field measurements, data acquisition and analysis (author). 80 refs., 347 figs.

  20. Flow-induced vibration of circular cylindrical structures

    Chen, S.S.

    1985-06-01

    This report summarizes the flow-induced vibration of circular cylinders in quiescent fluid, axial flow, and crossflow, and applications of the analytical methods and experimental data in design evaluation of various system components consisting of circular cylinders. 219 figs., 30 tabs. (JDB)

  1. Flow-induced vibration of circular cylindrical structures

    This report summarizes the flow-induced vibration of circular cylinders in quiescent fluid, axial flow, and crossflow, and applications of the analytical methods and experimental data in design evaluation of various system components consisting of circular cylinders. 219 figs., 30 tabs

  2. Laser-induced vibrational dynamics of ozone in solid argon

    Hansen, Flemming Yssing; Amstrup, B.; Henriksen, Niels Engholm

    We consider the vibrational dynamics, induced by an intense infrared laser pulse, in an ozone molecule with isotopic substitution, that is, (OOO)-O-16-O-16-O-18 and compare the dynamics in the gas phase and in solid ar on. not perturbed by argon on a time-scale of a few picoseconds and selective...

  3. Analysis of flow-induced vibrations in the PEC design

    This paper summarizes the studies performed for the Italian PEC fast reactor test facility with regard to flow-induced vibration problems. Reference is made to the reactor-block, the primary and secondary coolant loops and the emergency loops. Studies in progress and future developments foreseen are also mentioned. (author)

  4. Analysis of flow induced vibration in heat exchangers

    A description will be given of three different types of heat exchangers developed by the Dutch Nuclear Industry Group ''Neratoom'' in cooperation with TNO for the sodium-cooled fast breeder reactor SNR-300 at Kalkar. Moreover, the research related with flow induced vibrations carried out by TNO (Organization for Applied Scientific Research) will be presented. The flow induced forces on the tubes of the straight-tube steam generators were measured at the inlet and outlet section where partial crossflow occurs. With the measured flow induced forces the response of a tube was calculated as a function of the tube-to-supportbush clearances taking into account the non-linear damping effects from the sodium. The theoretical results showed that for this particular design no tube impact damage is to be expected which was confirmed later by a full scale experiment. Special attention will be devoted to the steam generator with helical-coil tube-bundles, where the sodium flows in a counter cross-flow over the tube-bundle. Extensive measurements of the power spectra of the flow induced forces were carried out since no information could be found in the literature. The vibration analysis will be presented and vibration modes of the entire bundle will be compared with experimentally obtained results. Finally a description of the vibration tests to be carried out on the intermediate heat exchanger (IHX) will be presented. (author)

  5. Flow induced vibrations in a PWR piping system

    During a recurring bench test of an operating system, high amplitude vibrations have been observed on a safety piping system of a nuclear power plant. Due to the source of the pumps, these vibrations lead to wear damage and it is therefore necessary to estimate the life time of the piping system. This paper describes the methodology used to study the dynamic behaviour and to analyze the damage of a piping system submitted to internal flow. Starting from an experimental modal analysis of the piping system when not i service, we analyse the main parameters of the mechanical behaviour. Following this analysis, we obtain a mechanical model fitting the first experimental modes. On this basis, we build a vibro-acoustical model. This model takes into account the influence of the acoustical pipe length, both above and below the mechanical part, the modelling of acoustical components, the speed of sound. We did not experimentally characterize the pumps. Therefore, we use a numerical model in order to simulate the behaviour of the pumps. This model is based on the theory of the transfer matrix and takes into account the geometric and the hydraulic characteristics of the pump.The modelling of both sources (suction and discharge) connected to the pump is formed by contributions from a source corresponding to the turbulent noise at low frequency, a source at blade passage frequency. This model has been experimentally validated in a laboratory. The final results of the modelling of the complete piping system are in a complete accord with experimental measurements. (author). 3 refs., 7 figs

  6. Specialists meeting on LMFBR flow induced vibrations. Summary report

    A Specialists' Meeting on LMFBR Flow-Induced Vibrations was held at ANL in the United States which was sponsored by the International Atomic Energy Agency (IAEA) on the recommendations of the International Working Group on Fast Reactors (IWGFR). It was attended by participants from France, the Federal Republic of Germany, Italy, Japan, Netherlands, the United Kingdom, the Union of Soviet Socialist Republics, the United States and the IAEA. The purpose of the meeting was to provide, for the first time, a common forum for the exchange of information on flow-induced vibration programs of the member countries. As this was a first meeting, information was sought in the broad areas of: 1. Design Criteria and Problem Areas in LMFBR Design; 2. Current Design Procedures; and 3. Ongoing Research. A session was devoted to each of the above topics wherein papers were presented and discussed followed by open discussions on the session topic. The objective of the open discussions was to identify, from a review of specific reactor designs, (a) flow induced vibration problem areas (expected and observed) and their potential for occurrence; (b) failure modes and associated design criteria; (c) specific components that are susceptible to flow induced vibration; and (d) probable excitation mechanisms. It was aimed to assess the current state-of-the-art in designing to avoid flow induced vibration with consideration of licensing requirements; to evaluate existing methods of analysis, testing, and surveillance, along with their limitations and to identify areas requiring research and review ongoing research programmes relative to these research needs

  7. Influence of surface acoustic waves induced acoustic streaming on the kinetics of electrochemical reactions

    Tietze, Sabrina; Schlemmer, Josefine; Lindner, Gerhard

    2013-12-01

    The kinetics of electrochemical reactions is controlled by diffusion processes of charge carriers across a boundary layer between the electrode and the electrolyte, which result in a shielding of the electric field inside the electrolyte and a concentration gradient across this boundary layer. In accumulators the diffusion rate determines the rather long time needed for charging, which is a major drawback for electric mobility. This diffusion boundary can be removed by acoustic streaming in the electrolyte induced by surface acoustic waves propagating of the electrode, which results in an increase of the charging current and thus in a reduction of the time needed for charging. For a quantitative study of the influence of acoustic streaming on the charge transport an electropolishing cell with vertically oriented copper electrodes and diluted H3PO4-Propanol electrolytes were used. Lamb waves with various excitation frequencies were exited on the anode with different piezoelectric transducers, which induced acoustic streaming in the overlaying electrolytic liquid. An increase of the polishing current of up to approximately 100 % has been obtained with such a set-up.

  8. Flow induced vibrations in liquid metal fast breeder reactors

    Flow induced vibrations are well known phenomena in industry. Engineers have to estimate their destructive effects on structures. In the nuclear industry, flow induced vibrations are assessed early in the design process, and the results are incorporated in the design procedures. In many cases, model testing is used to supplement the design process to ensure that detrimental behaviour due to flow induced vibrations will not occur in the component in question. While these procedures attempt to minimize the probability of adverse performance of the various components, there is a problem in the extrapolation of analytical design techniques and/or model testing to actual plant operation. Therefore, sodium tests or vibrational measurements of components in the reactor system are used to provide additional assurance. This report is a general survey of experimental and calculational methods in this area of structural mechanics. The report is addressed to specialists and institutions in industrialized and developing countries who are responsible for the design and operation of liquid metal fast breeder reactors. 92 refs, 90 figs, 8 tabs

  9. Geodesic Acoustic Modes Induced by Energetic Particles

    Zhou, Tianchun; Berk, Herbert

    2009-11-01

    A global geodesic acoustic mode driven by energetic particles (EGAM) has been observed in JET[1, 2] and DIII D[3, 4]. The mode is to be treated fully kinetically. The descriptions of the background electrons and ions are based on standard high and low bounce frequency expansion respectively with respect to the mode frequency. However, the energetic ions must be treated without any expansion of ratio between their bounce frequency and the mode frequency since they are comparable. Under electrostatic perturbation, we construct a quadratic form for the wave amplitude, from which an integro-differential equation is derived. In the limit where the drift orbit width is small comparison with the mode width, a differential equation for perturbed electrostatic field is obtained. Solution is obtained both analytically and numerically. We find that beam counterinjection enhances the instability of the mode. Landau damping due to thermal species is investigated.

  10. Piezoelectric energy harvesting from traffic-induced bridge vibrations

    This paper focuses on energy harvesting from traffic-induced vibrations in bridges. Using a pre-stressed concrete highway bridge as a case study, in situ vibration measurements are presented and analysed. From these results, a prototype of a cantilever piezoelectric harvester is designed, tested and modelled. Even though the considered bridge vibrations are characterized by small amplitude and a low frequency (i.e. below 15 Hz), it is shown that mean power of the order of 0.03 mW can be produced, with a controlled voltage between 1.8 and 3.6 V. A simple model is proposed for theoretical prediction of the delivered power in terms of traffic intensity. This model shows good agreement with the experimental results and leads to a simple but effective design rule for piezoelectric harvesters to be used on bridges. (paper)

  11. Flow induced vibration characteristics of two circular cylinders in a side by side arrangement and the vibration mechanism

    This experimental study investigated the characteristics of flow induced vibration of two elastically supported circular cylinders in a side by side arrangement. In particular, the characteristics of the flow induced vibration of the two cylinders are investigated by changing the flow speed at each spacing ratio L/D (L is the space between two cylinders and D is the diameter of the cylinder). To clarify the mechanism generating the flow induced vibration of the cylinders, the flow patterns around the two vibrating cylinders are also investigated using a flow visualization test that reproduces the flow induced vibration of the cylinders with a forced vibration apparatus. As a result, it is clarified that the flow induced vibration characteristics of the two cylinders arranged side by side switch among four patterns as the flow between the two cylinders is switched. Among the three arrangements considered (tandem, staggered, and side by side), the arrangement that generates flow induced vibration of the two cylinders most easily is the side by side arrangement

  12. High Resolution X-ray-Induced Acoustic Tomography

    Xiang, Liangzhong; Tang, Shanshan; Ahmad, Moiz; Xing, Lei

    2016-05-01

    Absorption based CT imaging has been an invaluable tool in medical diagnosis, biology, and materials science. However, CT requires a large set of projection data and high radiation dose to achieve superior image quality. In this letter, we report a new imaging modality, X-ray Induced Acoustic Tomography (XACT), which takes advantages of high sensitivity to X-ray absorption and high ultrasonic resolution in a single modality. A single projection X-ray exposure is sufficient to generate acoustic signals in 3D space because the X-ray generated acoustic waves are of a spherical nature and propagate in all directions from their point of generation. We demonstrate the successful reconstruction of gold fiducial markers with a spatial resolution of about 350 μm. XACT reveals a new imaging mechanism and provides uncharted opportunities for structural determination with X-ray.

  13. An Intelligent Sensor Array Distributed System for Vibration Analysis and Acoustic Noise Characterization of a Linear Switched Reluctance Actuator

    Maria Calado

    2012-06-01

    Full Text Available This paper proposes a distributed system for analysis and monitoring (DSAM of vibrations and acoustic noise, which consists of an array of intelligent modules, sensor modules, communication bus and a host PC acting as data center. The main advantages of the DSAM are its modularity, scalability, and flexibility for use of different type of sensors/transducers, with analog or digital outputs, and for signals of different nature. Its final cost is also significantly lower than other available commercial solutions. The system is reconfigurable, can operate either with synchronous or asynchronous modes, with programmable sampling frequencies, 8-bit or 12-bit resolution and a memory buffer of 15 kbyte. It allows real-time data-acquisition for signals of different nature, in applications that require a large number of sensors, thus it is suited for monitoring of vibrations in Linear Switched Reluctance Actuators (LSRAs. The acquired data allows the full characterization of the LSRA in terms of its response to vibrations of structural origins, and the vibrations and acoustic noise emitted under normal operation. The DSAM can also be used for electrical machine condition monitoring, machine fault diagnosis, structural characterization and monitoring, among other applications.

  14. Detection of vibrational-overtone excitation in water via laser-induced grating spectroscopy

    In this paper we describe a method, based on the laser-induced grating technique, for studying the spectroscopy of vibrational overtone-excited gas-phase water. Two phase-coherent visible laser beams whose frequencies are in the range of the third overtone of the OH stretch in water are crossed in the gas-phase sample. As the wavelength of these excitation beams is scanned through individual rovibrational OH overtone transitions, vibrational energy is deposited into the water in a spatially sinusoidal pattern. A fixed-frequency 266 nm probe laser beam is diffracted from the resultant transmission diffraction grating in water. We show that under collision-free conditions, probe laser diffraction is observed from the initially excited grating, which is a necessary condition for using this technique to study the absorption spectroscopy of the vibrationally excited molecules. Under multiple collision conditions, a probe laser wavelength-independent refractive index grating is formed within the bulk sample. In addition, we observe temporal oscillations in the grating diffraction efficiency arising from excitation of standing acoustic waves

  15. Experimental Study on the Measurement of Water Bottom Vibration Induced by Underwater Drilling Blasting

    Gu Wenbin; Chen Jianghai; Wang Zhenxiong; Wang Zhihua; Liu Jianqing; Lu Ming

    2015-01-01

    Due to the lack of proper instrumentations and the difficulties in underwater measurements, the studies about water bottom vibration induced by underwater drilling blasting are seldom reported. In order to investigate the propagation and attenuation laws of blasting induced water bottom vibration, a water bottom vibration monitor was developed with consideration of the difficulties in underwater measurements. By means of this equipment, the actual water bottom vibration induced by underwater ...

  16. Flow-induced vibration of component cooling water heat exchangers

    This paper presents an evaluation of flow-induced vibration problems of component cooling water heat exchangers in one of Taipower's nuclear power stations. Specifically, it describes flow-induced vibration phenomena, tests to identify the excitation mechanisms, measurement of response characteristics, analyses to predict tube response and wear, various design alterations, and modifications of the original design. Several unique features associated with the heat exchangers are demonstrated, including energy-trapping modes, existence of tube-support-plate (TSP)-inactive modes, and fluidelastic instability of TSP-active and -inactive modes. On the basis of this evaluation, the difficulties and future research needs for the evaluation of heat exchangers are identified. 11 refs., 19 figs., 3 tabs

  17. Light-induced vibration in the hearing organ

    Ren, Tianying; He, Wenxuan; Li, Yizeng; Grosh, Karl; Fridberger, Anders

    2014-01-01

    The exceptional sensitivity of mammalian hearing organs is attributed to an active process, where force produced by sensory cells boost sound-induced vibrations, making soft sounds audible. This process is thought to be local, with each section of the hearing organ capable of amplifying sound-evoked movement, and nearly instantaneous, since amplification can work for sounds at frequencies up to 100 kHz in some species. To test these fundamental precepts, we developed a method for focally stim...

  18. CFD Simulation of Vortex Induced Vibration of a Cylindrical Structure

    Asyikin, Muhammad Tedy

    2012-01-01

    This thesis presents the investigation of the flow characteristic and vortex induced vibration (VIV) of a cylindrical structure due to the incompressible laminar and turbulent flow at Reynolds number 40, 100, 200 and 1000. The simulations were performed by solving the steady and transient (unsteady) 2D Navier-Stokes equation. For Reynolds number 40, the simulations were set as a steady and laminar flow and the SIMPLE and QUICK were used as the pressure-velocity coupling scheme and momentum sp...

  19. Evaluation of human-induced vibration of continuous footbridges

    El-Robaa Ahmed; Gaawan Sameh; Malek Charles

    2015-01-01

    With the development of construction materials and the introduction of high strength steel and concrete, the human-induced vibration became a dominant criterion for the design of pedestrian bridges. Currently, longer spans and lightweight bridges have been comprised in most of design trends. This leads to lower the natural frequencies of the system which have a great effect on the dynamic performance of bridges subjected to human activities. Although the design of steel footbridges could reac...

  20. Acoustic-induced motion of the bushcricket (Mecopoda elongata, Tettigoniidae) tympanum.

    Nowotny, Manuela; Hummel, Jennifer; Weber, Melanie; Möckel, Doreen; Kössl, Manfred

    2010-12-01

    Bushcrickets have a tonotopically organised hearing organ, the so-called crista acustica, in the tibia of the forelegs. This organ responds to a frequency range of about 5-80 kHz and lies behind the anterior tympanum on top of a trachea branch. We analyzed the sound-induced vibration pattern of the anterior tympanum, using a Laser-Doppler-Vibrometer Scanning microscope system, in order to identify frequency-dependent amplitude and phase of displacement. The vibration pattern evoked by a frequency sweep (4-79 kHz) showed an amplitude maximum which would correspond to the resonance frequency of an open tube system. At higher frequencies of about 30 kHz a difference in the amplitude and phase response between the distal and the proximal part of the tympanum was detected. The inner plate of the tympanum starts to wobble at this frequency. This higher mode in the motion pattern is not explained by purely acoustic characteristics of the tracheal space below the tympanum but may depend on the mechanical impedance of the tympanum plate. In accordance with a previous hypothesis, the tympanum moves over the whole tested frequency range in the dorso-ventral direction like a hinged flap with the largest displacement in its ventral part and no higher modes of vibration. PMID:20827480

  1. Efficient Structure Resonance Energy Transfer from Microwaves to Confined Acoustic Vibrations in Viruses

    Yang, Szu-Chi; Lin, Huan-Chun; Liu, Tzu-Ming; Lu, Jen-Tang; Hung, Wan-Ting; Huang, Yu-Ru; Tsai, Yi-Chun; Kao, Chuan-Liang; Chen, Shih-Yuan; Sun, Chi-Kuang

    2015-12-01

    Virus is known to resonate in the confined-acoustic dipolar mode with microwave of the same frequency. However this effect was not considered in previous virus-microwave interaction studies and microwave-based virus epidemic prevention. Here we show that this structure-resonant energy transfer effect from microwaves to virus can be efficient enough so that airborne virus was inactivated with reasonable microwave power density safe for the open public. We demonstrate this effect by measuring the residual viral infectivity of influenza A virus after illuminating microwaves with different frequencies and powers. We also established a theoretical model to estimate the microwaves power threshold for virus inactivation and good agreement with experiments was obtained. Such structure-resonant energy transfer induced inactivation is mainly through physically fracturing the virus structure, which was confirmed by real-time reverse transcription polymerase chain reaction. These results provide a pathway toward establishing a new epidemic prevention strategy in open public for airborne virus.

  2. Passive acoustic radiation control for a vibrating panel with piezoelectric shunt damping circuit using particle swarm optimization algorithm

    This paper presents a new acoustic radiation optimization method for a vibrating panel-like structure with a passive piezoelectric shunt damping system in order to minimize well-radiating modes generated from the panel. The optimization method is based on an idea of using the p-version finite element method(p-version FEM), the boundary element method(BEM), and the particle swarm optimization algorithm(PSOA). Optimum embossment design for the vibrating panel using the PSOA is first investigated in order to minimize noise radiation over a frequency range of interest. The optimum embossment design works as a kind of stiffener so that well-radiating natural modes are shifted up with some degrees. The optimized panel, however, may still require additional damping for attenuating the peak acoustic amplitudes. A passive shunt damping system is thus employed to additionally damp the well-radiating modes from the optimized panel. To numerically evaluate the acoustic multiple-mode damping capability by a shunt damping system, the integrated p-version FEM/BEM for the panel with the shunt damping system is modeled and developed by MATLAB. Using the PSOA, the optimization technique for the optimal multiple-mode shunt damper is investigated in order to achieve the optimum damping performance for the well-radiating modes simultaneously. Also, the acoustic damping performance of the shunt damping circuit in the acoustic environment is demonstrated numerically and experimentally with respect to the realistically sized panel. The simulated result shows a good agreement with that of the experimental result

  3. Heterogeneous Nucleation Induced by Capillary Wave During Acoustic Levitation

    吕勇军; 解文军; 魏炳波

    2003-01-01

    The rapid solidification of acoustically levitated drops of Pb-61.9 wt. %Sn eutectic alloy is accomplished. A surface morphology of spreading ripples is observed on a sample undercooled by 15 K. The ripples originate from the centre of sample surface, which is also the heterogeneous nucleation site for eutectic growth. The Faraday instability excited by forced surface vibration has brought about these ripples. They are retained in the solidified sample if the sound pressure level exceeds the threshold pressure required for the appearance of capillary waves.Theoretical calculations indicate that both the pressure and displacement maxima exist in the central part of a levitated drop. The pressure near the sample centre can promote heterogeneous nucleation, which is in agreement qualitatively with the experimental results.

  4. Evaluation of human-induced vibration of continuous footbridges

    El-Robaa Ahmed

    2015-01-01

    Full Text Available With the development of construction materials and the introduction of high strength steel and concrete, the human-induced vibration became a dominant criterion for the design of pedestrian bridges. Currently, longer spans and lightweight bridges have been comprised in most of design trends. This leads to lower the natural frequencies of the system which have a great effect on the dynamic performance of bridges subjected to human activities. Although the design of steel footbridges could reach the optimum level of design in terms of strength criterion, it might not reach the acceptance level for vibration condition. This will enforce the designer to choose section profiles with higher inertia to enhance stiffness of the whole system. This paper presents an overall assessment for floor vibration problem due to pedestrian induced vertical forces on continuous composite footbridges. The footfall method presented by concrete centre “CCIP-016” is adopted in this study to evaluate the response factor and acceleration of pedestrian bridges using a FEA software package “Robot Structural Analysis”.

  5. Road vehicle-induced vibration control of microelectronics facilities

    Guo Anxin; Xu Youlin; Li Hui

    2005-01-01

    A hybrid control platform is investigated in this paper to mitigate microvibrations to a group of vibrationsensitive equipment installed in a microelectronics facility subject to nearby road vehicle-induced horizontal and vertical ground motions. The hybrid control platform, on which microelectronics equipment is installed, is mounted on a building floor through a series of passive mounts and controlled by hydraulic actuators in both horizontal and vertical directions. The control platform is an elastic body with significant bending modes of vibration, and a sub-optimal control algorithm is used to manipulate the hydraulic actuators with actuator dynamics included. The finite element model and the equations of motion of the coupled platform-building system are then established in the absolute coordinate to facilitate the feedback control and performance evaluation of the platform. The horizontal and vertical ground vibrations at the base of the building induced by nearby moving road vehicles are assumed to be stationary random processes. A typical three-story microelectronics building is selected as a case study. The case study shows that the vertical vibration of the microelectronics building is higher than the horizontal. The use of a hybrid control platform can effectively reduce both horizontal and vertical microvibrations of the microelectronics equipment to the level which satisfies the stringent microscale velocity requirement specified in the Bolt Beranek & Newman (BBN) criteria.

  6. Numerical simulation of flow-induced vibrations in tube bundles

    Full text of publication follows: In many industrial components mechanical structures like rod cluster control assembly, fuel assembly and heat exchanger tube bundles are submitted to complex flows causing possible vibrations and damage. Fluid forces are usually split into two parts: structure motion independent forces and fluid-elastic forces coupled with tube motion and responsible for possible dynamic instability development leading to possible short term failures through high amplitude vibrations. Most classical fluid force identification methods rely on structure response experimental measurements associated with convenient data processes. Owing to recent improvements in Computational Fluid Dynamics (C.F.D.), numerical fluid force identification is now practicable in the presence of industrial configurations. The present paper is devoted to numerical simulation of flow-induced vibrations of tube bundles submitted to single-phase cross flows by using C.F.D. codes. Direct Numerical Simulation (D.N.S.), Arbitrary Lagrange Euler formulation (A.L.E.) and code coupling process are involved to predict fluid forces responsible for tube bundle vibrations in the presence of fluid structure and fluid-elastic coupling effects. In the presence of strong multi-physics coupling, simulation of flow-induced vibrations requires a fluid structure code coupling process. The methodology consists in solving in the same time thermohydraulics and mechanics problems by using an A.L.E. formulation for the fluid computation. The purpose is to take into account coupling between flow and structure motions in order to be able to capture coupling effects. From a numerical point of view, there are three steps in the computation: the fluid problem is solved on the computational domain; fluid forces acting on the moving tube are estimated; finally they are introduced in the structure solver providing the tube displacement that is used to actualize the fluid computational domain. Specific

  7. Response characteristics and suppression of flow-induced vibrations of rectangular prisms with rotary oscillation. 1st report, response characteristics and generation mechanism of flow-induced vibrations

    The response characteristics and suppression of flow-induced vibration of rectangular prisms with various width-to-height ratios were experimentally investigated. The present study focused on rotary oscillation, which is one of flow-induced vibrations generated in a rectangular prism. In this paper, the response characteristics on elastically supported prism were first examined in detail by free-vibration test. Next, flow-induced vibrations obtained by the free-vibration test were reproduced by forced-vibration test, and then the generation mechanism of flow-induced vibrations was examined on the basis of the visualized flow patterns, fluctuating pressure distributions of the surface of prism and characteristics of flow-induced vibrations by the flow control. The main findings were that (1) there are three types of flow-induced vibrations, i.e., vortex excitation, low-speed torsion flutter and high-speed torsion flutter, (2) flow-induced vibrations can be classified into six patterns depending on the width-to-height ratio, (3) flow-induced vibrations occur due to change in fluctuating pressure on the surface of the prism based on the difference of the behavior of the shear layer separating from the leading edge, the impinging leading-edge vortex, and the wake vortices, and (4) generation of low-speed torsion flutter and vortex excitation is completely suppressed by adopting large values of the reduced mass-damping factor, however, high-speed torsion flutter occurs regardless of the reduced mass-damping factor. (author)

  8. An experimental study of vibration based energy harvesting in dynamically tailored structures with embedded acoustic black holes

    Zhao, Liuxian; Conlon, Stephen C.; Semperlotti, Fabio

    2015-06-01

    In this paper, we present an experimental investigation on the energy harvesting performance of dynamically tailored structures based on the concept of embedded acoustic black holes (ABHs). Embedded ABHs allow tailoring the wave propagation characteristics of the host structure creating structural areas with extreme levels of energy density. Experiments are conducted on a tapered plate-like aluminum structure with multiple embedded ABH features. The dynamic response of the structure is tested via laser vibrometry in order to confirm the vibration localization and the passive wavelength sweep characteristic of ABH embedded tapers. Vibrational energy is extracted from the host structure and converted into electrical energy by using ceramic piezoelectric discs bonded on the ABHs and shunted on an external electric circuit. The energy harvesting performance is investigated both under steady state and transient excitation. The experimental results confirm that the dynamic tailoring produces a drastic increase in the harvested energy independently from the nature of the excitation input.

  9. Structural vibration and fluid-borne noise induced by turbulent flow through a 90° piping elbow with/without a guide vane

    The structural vibration and fluid-borne noise induced by turbulent flow through a 90° piping elbow is studied and the effect of guide vanes in different positions installed at the elbow on the flow-induced vibration and flow-induced noise is investigated. Large Eddy Simulation (LES) model is adopted to solve for time varying pressure and velocity fields. The structural vibration is investigated based on a fluid–structure interaction (FSI) code using harmonic response analysis. The computation of hydrodynamic noise is based on a hybrid LES/Lighthill's acoustic analogy method and sound sources are solved as volume sources in commercial software ACTRAN. The numerical results indicate that the guide vane at the right location is effective in reducing vibration and flow-induced noise in the 90° piping elbow with water. The ideal position of the guide vane is determined and some useful engineering conclusions are drawn. - Highlights: • Vibration and noise induced by turbulent flow through an elbow is analyzed. • The guide vane can decrease fluctuations of the turbulent flows. • The guide vane is effective in reducing vibration and noise of the elbow. • The ideal position of the guide vane installed at the elbow is determined

  10. Dose-response patterns for vibration-induced white finger

    Griffin, M; Bovenzi, M.; Nelson, C

    2003-01-01

    Aims: To investigate alternative relations between cumulative exposures to hand-transmitted vibration (taking account of vibration magnitude, lifetime exposure duration, and frequency of vibration) and the development of white finger (Raynaud's phenomenon).

  11. Two-phase flow induced vibrations in CANDU steam generators

    The U-Bend region of nuclear steam generators tube bundles have suffered from two-phase cross flow induced vibrations. Tubes in this region have experienced high amplitude vibrations leading to catastrophic failures. Turbulent buffeting and fluid-elastic instability has been identified as the main causes. Previous investigations have focused on flow regime and two-phase flow damping ratio. However, tube bundles in steam generators have vapour generated on the surface of the tubes, which might affect the flow regime, void fraction distribution, turbulent intensity levels and tube-flow interaction, all of which have the potential to change the tube vibration response. A cantilevered tube bundle made of electric cartridges heaters was built and tested in a Freon-11 flow loop at McMaster University. Tubes were arranged in a parallel triangular configuration. The bundle was exposed to two-phase cross flows consisting of different combinations of void from two sources, void generated upstream of the bundle and void generated at the surface of the tubes. Tube tip vibration response was measured optically and void fraction was measured by gamma densitometry technique. It was found that tube vibration amplitude in the transverse direction was reduced by a factor of eight for void fraction generated at the tube surfaces only, when compared to the upstream only void generation case. The main explanation for this effect is a reduction in the correlation length of the turbulent buffeting forcing function. Theoretical calculations of the tube vibration response due to turbulent buffeting under the same experimental conditions predicted a similar reduction in tube amplitude. The void fraction for the fluid-elastic instability threshold in the presence of tube bundle void fraction generation was higher than that for the upstream void fraction generation case. The first explanation of this difference is the level of turbulent buffeting forces the tube bundle was exposed to

  12. Laser induced vibration of a thin soap film.

    Emile, Olivier; Emile, Janine

    2014-01-01

    We report on the vibration of a thin soap film based on the optical radiation pressure force. The modulated low power laser induces a counter gravity flow in a vertical free standing draining film. The thickness of the soap film is then higher in the upper region than in the lower region of the film. Moreover, the lifetime of the film is dramatically increased by a factor of 2. Since the laser beam only acts mechanically on the film interfaces, such a film can be implemented in an optofluidic...

  13. Vibrationally-induced electronic population inversion with strong femtosecond pulses

    Sampedro, Pablo; Sola, Ignacio R

    2016-01-01

    We discover a new mechanism of electronic population inversion using strong femtosecond pulses, where the transfer is mediated by vibrational motion on a light-induced potential. The process can be achieved with a single pulse tuning its frequency to the red of the Franck-Condon window. We show the determinant role that the sign of the slope of the transition dipole moment can play on the dynamics, and extend the method to multiphoton processes with odd number of pulses. As an example, we show how the scheme can be applied to population inversion in Na2.

  14. Predicting vibration-induced displacement for a resonant friction slider

    Fidlin, A.; Thomsen, Jon Juel

    2001-01-01

    A mathematical model is set up to quantify vibration-induced motions of a slider, sandwiched between friction layers with different coefficients of friction, and equipped with an imbedded resonator that oscillates at high frequency and small amplitude. This model is highly nonlinear, involving non......-smooth functions with strong harmonic excitation terms. The method of averaging is extended to hold for systems of this class, and used to derive approximate expressions for predicting average velocities of the slider. These expressions are shown to produce results that agree very well with numerical integration...... of the full equations of motion. The expressions are used to estimate and explain the influence of system parameters....

  15. Laser-induced vibrational dynamics of ozone in solid argon

    Hansen, Flemming Yssing; Amstrup, B.; Henriksen, Niels Engholm

    1997-01-01

    We consider the vibrational dynamics, induced by an intense infrared laser pulse, in an ozone molecule with isotopic substitution, that is, (OOO)-O-16-O-16-O-18 and compare the dynamics in the gas phase and in solid ar on. not perturbed by argon on a time-scale of a few picoseconds and selective...... bond-breaking in the molecule should be possible following the same laser control scheme as suggested in the gas phase. (C) 1997 Elsevier Science B.V....

  16. Flow-induced vibration signal analysis of the FIV test loop

    Vibration spectrums of the test loop according to flow conditions were analyzed in order to identify the sources of vibration at peak frequencies. While a flow condition of the sweep test was changed by varying pump rotational speed from 450 rpm to 1500 rpm by the step 150 rpm, mid span acceleration of the test section in width-direction and dynamic pressure perturbation in the test section were measured. Other sources of vibration due to the flow structure interactions, such as acoustic resonance, blade pulsing frequency and bellows wrinkles, were investigated. Pressure perturbation in the section and acoustic resonance due to branch pipe give major effects to the vibration of the test section in high frequency range of 1.5 kHz to 2.8 kHz

  17. Regional distribution of acoustic-based lung vibration as a function of mechanical ventilation mode

    Dellinger, R Phillip; Jean, Smith; Cinel, Ismail; Tay, Christina; Rajanala, Susmita; Glickman, Yael A; Parrillo, Joseph E

    2007-01-01

    Introduction There are several ventilator modes that are used for maintenance mechanical ventilation but no conclusive evidence that one mode of ventilation is better than another. Vibration response imaging is a novel bedside imaging technique that displays vibration energy of lung sounds generated during the respiratory cycle as a real-time structural and functional image of the respiration process. In this study, we objectively evaluated the differences in regional lung vibration during di...

  18. Distributed Fiber-Optic Sensor for Detection and Localization of Acoustic Vibrations

    Sifta Radim

    2015-03-01

    Full Text Available A sensing system utilizing a standard optical fiber as a distributed sensor for the detection and localization of mechanical vibrations is presented. Vibrations can be caused by various external factors, like moving people, cars, trains, and other objects producing mechanical vibrations that are sensed by a fiber. In our laboratory we have designed a sensing system based on the Φ-OTDR (phase sensitive Optical Time Domain Reflectometry using an extremely narrow laser and EDFAs.

  19. Flow Induced Vibration Program at Argonne National Laboratory

    1984-01-01

    Argonne National Laboratory has had a Flow Induced Vibration Program since 1967; the Program currently resides in the Laboratory's Components Technology Division. Throughout its existence, the overall objective of the program has been to develop and apply new and/or improved methods of analysis and testing for the design evaluation of nuclear reactor plant components and heat exchange equipment from the standpoint of flow induced vibration. Historically, the majority of the program activities have been funded by the US Atomic Energy Commission (AEC), Energy Research and Development Administration (ERDA), and Department of Energy (DOE). Current DOE funding is from the Breeder Mechanical Component Development Division, Office of Breeder Technology Projects; Energy Conversion and Utilization Technology (ECUT) Program, Office of Energy Systems Research; and Division of Engineering, Mathematical and Geosciences, Office of Basic Energy Sciences. Testing of Clinch River Breeder Reactor upper plenum components has been funded by the Clinch River Breeder Reactor Plant (CRBRP) Project Office. Work has also been performed under contract with Foster Wheeler, General Electric, Duke Power Company, US Nuclear Regulatory Commission, and Westinghouse.

  20. Flow Induced Vibration Program at Argonne National Laboratory

    Argonne National Laboratory has had a Flow Induced Vibration Program since 1967; the Program currently resides in the Laboratory's Components Technology Division. Throughout its existence, the overall objective of the program has been to develop and apply new and/or improved methods of analysis and testing for the design evaluation of nuclear reactor plant components and heat exchange equipment from the standpoint of flow induced vibration. Historically, the majority of the program activities have been funded by the US Atomic Energy Commission (AEC), Energy Research and Development Administration (ERDA), and Department of Energy (DOE). Current DOE funding is from the Breeder Mechanical Component Development Division, Office of Breeder Technology Projects; Energy Conversion and Utilization Technology (ECUT) Program, Office of Energy Systems Research; and Division of Engineering, Mathematical and Geosciences, Office of Basic Energy Sciences. Testing of Clinch River Breeder Reactor upper plenum components has been funded by the Clinch River Breeder Reactor Plant (CRBRP) Project Office. Work has also been performed under contract with Foster Wheeler, General Electric, Duke Power Company, US Nuclear Regulatory Commission, and Westinghouse

  1. Experimental and analytical studies on pedestrian induced footbridge vibrations

    Gudmundsson, Gudmundur Valur; Ingólfsson, Einar Thór; Einarsson, Baldvin;

    2007-01-01

    models describing human-induced vibrations on structures in current literature and standards are explained, both for a single person walking or running and crowd loading. The measured vertical acceleration induced by single pedestrians was compared against the predictions and it was found that all the...... pacing rates large differences were observed between the measured acceleration response and the one predicted by the code. Instead, a slightly improved simplified load model using frequency dependent load factors gives better results....... modes corresponding to the measured values. The models were subsequently used to calculate the predicted acceleration according to the preliminary version of the Eurocode (ENV 1992-2: Concrete bridges) using time-history analysis with a moving load as representative for a single pedestrian. The load...

  2. Flow-induced vibration of steam generator tube bundles

    The vibrations induced in tube arrays by a transversal flow are of great practical interest because of their destructive effects especially on heat exchangers. Instabilities can appear beyond a critical flow velocity and induce very high vibratory levels which may involve fractures. These instabilities involve a fluidelastic coupling between the vibratory movement of the tubes and the flow round them. Studies are being carried out in France concerning steam generators. A lot of bundle mock-ups with various pitches have been tested and large range parameter domains have been investigated. In a second part, the C.E.A., FRAMATOME, E.D.F. and WESTINGHOUSE research program, which is being carried out, is presented

  3. Flow induced dust acoustic shock waves in a complex plasma

    Jaiswal, Surabhi; Bandyopadhyay, Pintu; Sen, Abhijit

    2015-11-01

    We report on experimental observations of particle flow induced large amplitude shock waves in a dusty plasma. These dust acoustic shocks (DAS) are observed for strongly supersonic flows and have been studied in a U-shaped Dusty Plasma Experimental (DPEx) device for charged kaolin dust in a background of Argon plasma. The strong flow of the dust fluid is induced by adjusting the pumping speed and neutral gas flow into the device. An isolated copper wire mounted on the cathode acts as a potential barrier to the flow of dust particles. A sudden change of the dust density near the potential hill is used to trigger the onset of high velocity dust acoustic shocks. The dynamics of the shocks are captured by fast video pictures of the structures that are illuminated by a laser sheet beam. The physical characteristics of the shock are delineated from a parametric scan of their dynamical properties over a range of plasma parameters and flow speeds. Details of these observations and a physical explanation based on model calculations will be presented.

  4. BVI induced vibration and noise alleviation by active and passive approaches

    Liu, Li

    This dissertation describes the development of a comprehensive aeroelastic/aeroacoustic simulation capability for the modeling of vibration and noise in rotorcraft induced by blade-vortex interaction (BVI). Subsequently this capability is applied to study vibration and noise reduction, using active and passive control approaches. The active approach employed is the actively controlled partial span trailing edge flaps (ACF), implemented in single and dual, servo and plain flap configurations. The passive approach is based on varying the sweep and anhedral on the tip of the rotor. Two different modern helicopters are chosen as the baseline for the implementation of ACF approach, one resembling a four-bladed MBB BO-105 hingeless rotor and the other similar to a five-bladed MD-900 bearingless rotor. The structural model is based on a finite element approach capable of simulating composite helicopter blades with swept tips, and representing multiple load paths at the blade root which is a characteristic of bearingless rotors. An unsteady compressible aerodynamic model based on a rational function approximation (RFA) approach is combined with a free wake analysis which has been enhanced by improving the wake analysis resolution and modeling a dual vortex structure. These enhancements are important for capturing BVI effects. A method for predicting compressible unsteady blade surface pressure distribution on rotor blades has been developed, which is required by the acoustic analysis. A modified version of helicopter noise code WOPWOP with provisions for blade flexibility has been combined with the aeroelastic analysis to predict the BVI noise. Several variants of the higher harmonic control (HHC) algorithm have been applied for the active noise control, as well as the simultaneous vibration and noise control. Active control of BVI noise is accomplished using feedback from an onboard microphone. The simulation has been extensively validated against experimental data and

  5. Flow-induced noise and vibration analysis of a piping elbow with/without a guide vane

    Zhang, Tao; Zhang, Yong'ou; Ouyang, Huajiang; Guo, Tao

    2014-12-01

    The effect of a guide vane installed at the elbow on flow-induced noise and vibration is investigated in the range of Reynolds numbers from 1.70×105 to 6.81×105, and the position of guide vane is determined by publications. The turbulent flow in the piping elbow is simulated with large eddy simulation (LES). Following this, a hybrid method of combining LES and Lighthill's acoustic analogy theory is used to simulate the hydrodynamic noise and sound sources are solved as volume sources in code Actran. In addition, the flow-induced vibration of the piping elbow is investigated based on a fluid-structure interaction (FSI) code. The LES results indicate that the range of vortex zone in the elbow without the guide vane is larger than the case with the guide vane, and the guide vane is effective in reducing flow-induced noise and vibration in the 90° piping elbow at different Reynolds numbers.

  6. Relationship between sound radiation from sound-induced and force-excited vibration: Analysis using an infinite elastic plate model.

    Yairi, Motoki; Sakagami, Kimihiro; Nishibara, Kosuke; Okuzono, Takeshi

    2016-07-01

    Although sound radiation from sound-induced vibration and from force-excited vibration of solid structures are similar phenomena in terms of radiating from vibrating structures, the general relationship between them has not been explicitly studied to date. In particular, airborne sound transmission through walls and sound radiation from structurally vibrating surfaces in buildings are treated as different issues in architectural acoustics. In this paper, a fundamental relationship is elucidated through the use of a simple model. The transmission coefficient for random-incidence sound and the radiated sound power under point force excitation of an infinite elastic plate are both analyzed. Exact and approximate solutions are derived for the two problems, and the relationship between them is theoretically discussed. A conversion function that relates the transmission coefficient and radiated sound power is obtained in a simple closed form through the approximate solutions. The exact solutions are also related by the same conversion function. It is composed of the specific impedance and the wavenumber, and is independent of any elastic plate parameters. The sound radiation due to random-incidence sound and point force excitation are similar phenomena, and the only difference is the gradient of those characteristics with respect to the frequency. PMID:27475169

  7. Design of CAP1400 reactor internals flow-induced vibration simulation test model

    While the first CAP1400 reactor internals is defined as a 'prototype', it is necessary to carry out the reactor internals flow-induced vibration simulation test for verifying the structure integrity of reactor internals and providing data for vibration assessment of CAP1400 reactor internals. The reactor internals flow-induced vibration simulation test is usually a reduced scale model test. This paper describes in detail the main factors of model scale, similarity criterion and the simplification of test model. The simplification of model will not only reduce the fabrication cost, but also obtain more accurate test data from the flow-induced vibration simulation test. (authors)

  8. A theoretical study of time-dependent, ultrasound-induced acoustic streaming in microchannels

    Muller, Peter Barkholt

    2015-01-01

    Based on first- and second-order perturbation theory, we present a numerical study of the temporal build-up and decay of unsteady acoustic fields and acoustic streaming flows actuated by vibrating walls in the transverse cross-sectional plane of a long straight microchannel under adiabatic conditions and assuming temperature-independent material parameters. The unsteady streaming flow is obtained by averaging the time-dependent velocity field over one oscillation period, and as time increases, it is shown to converge towards the well-known steady time-averaged solution calculated in the frequency domain. Scaling analysis reveals that the acoustic resonance builds up much faster than the acoustic streaming, implying that the radiation force may dominate over the drag force from streaming even for small particles. However, our numerical time-dependent analysis indicates that pulsed actuation does not reduce streaming significantly due to its slow decay. Our analysis also shows that for an acoustic resonance wit...

  9. Added mass and critical mass in vortex induced vibration

    Konstantinidis, Efstathios

    2015-11-01

    The critical mass phenomenon is the observation that a circular cylinder suspended freely in a fluid stream without a mechanical restoring force exhibits significant vortex induced vibration if its mass is below some value whereas insignificant vibration occurs if the mass is above this value. While the phenomenon is known, its origin remains largely unknown. Furthermore, there are several outstanding questions regarding this phenomenon which cannot be explained on the basis of the existing theoretical framework. In this work, a new formulation of the added mass in the context of potential flow is presented. This leads to a new expression for the potential force, which is more complex than the classical one, that is subsequently employed in simplified form in order to analytically model the flow-structure interaction by decomposing the fluid force into potential and vortex components via the equation of cylinder motion. It is found that the model predicts a significant increase in the amplitude response of a freely suspended cylinder in sharp contrast to predictions using the classical formulation of the added mass. Finally, the model equations are employed to exemplify the phenomenology of the critical mass in real flows.

  10. Theory and Techniques for Vibration-Induced Conductivity Fluctuation testing of Soils

    Chang, Hung-Chih; Kishne, Andrea; Morgan, Cristine; Kwan, Chiman; 10.1142/S021947750800443X

    2009-01-01

    First we present and theoretically analyze the phenomenological physical picture behind Vibration-Induced Conductivity Fluctuations. We identify the relevant tensors characterizing the electromechanical response against the vibrations for both longitudinal and transversal responses. We analyze the conductivity response with acceleration type vibrations and a new scheme, measurements with more advantageous compression type vibrations that are first introduced here. Compression vibrations provide sideband spectral lines shifted by the frequency of the vibration instead of its second harmonics; moreover the application of this method is less problematic with loose electrodes. Concerning geometry and electrodes, the large measurement errors in earlier experiment indicated electrode effects which justify using four-electrode type measurements. We propose and analyze new arrangements for the longitudinal and transversal measurements with both compression vibration and acceleration vibration for laboratory and field...

  11. AST Launch Vehicle Acoustics

    Houston, Janice; Counter, D.; Giacomoni, D.

    2015-01-01

    The liftoff phase induces acoustic loading over a broad frequency range for a launch vehicle. These external acoustic environments are then used in the prediction of internal vibration responses of the vehicle and components which result in the qualification levels. Thus, predicting these liftoff acoustic (LOA) environments is critical to the design requirements of any launch vehicle. If there is a significant amount of uncertainty in the predictions or if acoustic mitigation options must be implemented, a subscale acoustic test is a feasible pre-launch test option to verify the LOA environments. The NASA Space Launch System (SLS) program initiated the Scale Model Acoustic Test (SMAT) to verify the predicted SLS LOA environments and to determine the acoustic reduction with an above deck water sound suppression system. The SMAT was conducted at Marshall Space Flight Center and the test article included a 5% scale SLS vehicle model, tower and Mobile Launcher. Acoustic and pressure data were measured by approximately 250 instruments. The SMAT liftoff acoustic results are presented, findings are discussed and a comparison is shown to the Ares I Scale Model Acoustic Test (ASMAT) results.

  12. Acoustically induced optical second harmonic generation in hydrogenated amorphous silicon films

    Ebothe, J; Cabarrocas, P R I; Godet, C; Equer, B

    2003-01-01

    Acoustically induced second harmonic generation (AISHG) in hydrogenated amorphous silicon (a-Si : H) films of different morphology has been observed. We have found that with increasing acoustical power, the optical SHG of Gd : YAB laser light (lambda = 2.03 mu m) increases and reaches its maximum value at an acoustical power density of about 2.10 W cm sup - sup 2. With decreasing temperature, the AISHG signal strongly increases below 48 K and correlates well with the temperature behaviour of differential scanning calorimetry indicating near-surface temperature phase transition. The AISHG maxima were observed at acoustical frequencies of 10-11, 14-16, 20-22 and 23-26 kHz. The independently performed measurements of the acoustically induced IR spectra have shown that the origin of the observed phenomenon is the acoustically induced electron-phonon anharmonicity in samples of different morphology.

  13. Flow induced vibration analysis for preventing PWR fuel rods from excessive fretting wear

    In order to prevent PWR fuel rods excessive fretting wear, the author analysed flow induced vibration. The methods developed and used by FRAMATOME to analyze and to justify the fuel rod behaviour with respect to flow induced vibrations and wear at grid support locations were presented

  14. Dynamic Characteristics of Flow Induced Vibration in a Rotor-Seal System

    Nan Zhang

    2011-01-01

    Full Text Available Flow induced vibration is an important factor affecting the performance of the rotor-seal system. From the point of view of flow induced vibration, the nonlinear models of the rotor-seal system are presented for the analysis of the fluid force, which is induced by the interaction between the unstable fluid flow in the seal and the vibrating rotor. The nonlinear characteristics of flow induced vibration in the rotor-seal system are analyzed, and the nonlinear phenomena in the unbalanced rotor-seal system are investigated using the nonlinear models. Various nonlinear phenomena of flow induced vibration in the rotor-seal system, such as synchronization phenomenon and amplitude mutation, are reproduced.

  15. Visco-acoustic modelling of a vibrating plate interacting with water confined in a domain of micrometric size

    Lebental, B.; Bourquin, F.

    2012-04-01

    It is well established that concrete durability strongly depends on the capillary porosity of the material. Hence, structural health monitoring of concrete structure could take advantage of concrete microporosity monitoring. To this end, a new method for the in situ non-destructive testing of capillary porosity in cementitious materials has been proposed. A sensing device that seems well suited to this application is a capacitive ultrasonic transducer with a characteristic size of 1 μm. It is to be embedded in the material. Its vibrating membrane is made of aligned carbon nanotubes forming a thin layer with a typical thickness of 1 nm. It generates acoustic waves of micrometric wavelength into water-filled micropores, aiming at measuring their properties. The present paper focuses on the numerical simulation of the embedded sensor. In order to properly account for viscous effects in fluids at the micrometric scale, we have developed a specific computational method for the visco-acoustic modelling of a microplate vibrating between 10 MHz and 2 GHz in a water-filled domain of micrometric size. Our approach is based on the condensation of the fluid part of the fluid-structure problem on the structure by a finite element method, and on a spectral approximation of the structural equations. The numerical results indicate that the fluid domain is resonant despite the viscous terms, which causes a frequency downshift of the resonances and a decrease of the quality factor. In the coupled system, the plate does not perturb the fluid resonances, whereas the plate resonances are strongly upshifted by the water load. The resonance frequencies of the system are shown to display a clear dependence on the pore width, which makes the device a good candidate as a porosity sensor.

  16. Force Limiting Vibration Tests Evaluated from both Ground Acoustic Tests and FEM Simulations of a Flight Like Vehicle System Assembly

    Smith, Andrew; LaVerde, Bruce; Waldon, James; Hunt, Ron

    2014-01-01

    Marshall Space Flight Center has conducted a series of ground acoustic tests with the dual goals of informing analytical judgment, and validating analytical methods when estimating vibroacoustic responses of launch vehicle subsystems. The process of repeatedly correlating finite element-simulated responses with test-measured responses has assisted in the development of best practices for modeling and post-processing. In recent work, force transducers were integrated to measure interface forces at the base of avionics box equipment. Other force data was indirectly measured using strain gauges. The combination of these direct and indirect force measurements has been used to support and illustrate the advantages of implementing the Force Limiting approach for equipment qualification tests. The comparison of force response from integrated system level tests to measurements at the same locations during component level vibration tests provides an excellent illustration. A second comparison of the measured response cases from the system level acoustic tests to finite element simulations has also produced some principles for assessing the suitability of Finite Element Models (FEMs) for making vibroacoustics estimates. The results indicate that when FEM models are employed to guide force limiting choices, they should include sufficient detail to represent the apparent mass of the system in the frequency range of interest.

  17. Determination of hydrocarbon levels in water via laser-induced acoustics wave

    Bidin, Noriah; Hossenian, Raheleh; Duralim, Maisarah; Krishnan, Ganesan; Marsin, Faridah Mohd; Nughro, Waskito; Zainal, Jasman

    2016-04-01

    Hydrocarbon contamination in water is a major environmental concern in terms of foreseen collapse of the natural ecosystem. Hydrocarbon level in water was determined by generating acoustic wave via an innovative laser-induced breakdown in conjunction with high-speed photographic coupling with piezoelectric transducer to trace acoustic wave propagation. A Q-switched Nd:YAG (40 mJ) was focused in cuvette-filled hydrocarbon solution at various concentrations (0-2000 ppm) to induce optical breakdown, shock wave generation and later acoustic wave propagation. A nitro-dye (ND) laser (10 mJ) was used as a flash to illuminate and frozen the acoustic wave propagation. Lasers were synchronised using a digital delay generator. The image of acoustic waves was grabbed and recorded via charged couple device (CCD) video camera at the speed of 30 frames/second with the aid of Matrox software version 9. The optical delay (0.8-10.0 μs) between the acoustic wave formation and its frozen time is recorded through photodetectors. A piezo-electric transducer (PZT) was used to trace the acoustic wave (sound signal), which cascades to a digital oscilloscope. The acoustic speed is calculated from the ratio of acoustic wave radius (1-8 mm) and optical time delay. Acoustic wave speed is found to linearly increase with hydrocarbon concentrations. The acoustic signal generation at higher hydrocarbon levels in water is attributed to supplementary mass transfer and impact on the probe. Integrated high-speed photography with transducer detection system authenticated that the signals indeed emerged from the laser-induced acoustic wave instead of photothermal processes. It is established that the acoustic wave speed in water is used as a fingerprint to detect the hydrocarbon levels.

  18. Recent monitoring of the Øresund Bridge: Observations of rain-wind induced cable vibrations

    Acampora, Antonio; Georgakis, Christos

    2011-01-01

    In 1999, 2m amplitude cable vibrations were observed on the Øresund Bridge. The vibrations were attributed to a change in cable shape due to sleet accretion. Subsequent monitoring of the bridge, though, revealed other vibration events due to rain-wind induced mechanisms and parametric excitation...... diameters have been observed, although the most frequent observations are of smaller amplitude and are almost always in combination with rain. In this paper, several observations are made, regarding the rain-wind induced vibrations (RWIVs) of the cables, based on a relatively brief full-scale monitoring...... dampers were installed on the longest and second longest cable pairs. Although the bridge has not suffered from any significant vibration events since the installation of the new damping systems, smaller amplitude vibrations are recorded from time to time. Peak to peak amplitudes of up to three cable...

  19. Vibrational predissociation and vibrationally induced isomerization of 3-aminophenol-ammonia.

    Heid, Cornelia G; Merrill, Wyatt G; Case, Amanda S; Crim, F Fleming

    2015-01-01

    We investigate the vibrational predissociation dynamics of the hydrogen-bonded 3-aminophenol-ammonia cluster (3-AP-NH3) in the OH and NH stretching regions. Vibrational excitation provides enough energy to dissociate the cluster into its constituent 3-AP and NH3 monomers, and we detect the 3-AP fragments via (1 + 1) resonance-enhanced multiphoton ionization (REMPI). The distribution of vibrational states of the 3-AP fragment suggests the presence of two distinct dissociation pathways. The first dissociation channel produces a broad, unstructured feature in the REMPI-action spectrum after excitation of any of the OH or NH stretching vibrations, pointing to a nearly statistical dissociation pathway with extensive coupling among the vibrations in the cluster during the vibrational predissociation. The second dissociation channel produces distinct, resolved features on top of the broad feature but only following excitation of the OH or symmetric NH3 stretch in the cluster. This striking mode-specificity is consistent with strong coupling of these two modes to the dissociation coordinate (the O-H⋯N bond). The presence of clearly resolved transitions to the electronic origin and to the 10a(2) + 10b(2) state of the cis-3-AP isomer shows that vibrational excitation is driving the isomerization of the trans-3-AP-NH3 isomer to the cis-3-AP-NH3 isomer in the course of the dissociation. PMID:25573564

  20. Acoustics

    Goodman, Jerry R.; Grosveld, Ferdinand

    2007-01-01

    The acoustics environment in space operations is important to maintain at manageable levels so that the crewperson can remain safe, functional, effective, and reasonably comfortable. High acoustic levels can produce temporary or permanent hearing loss, or cause other physiological symptoms such as auditory pain, headaches, discomfort, strain in the vocal cords, or fatigue. Noise is defined as undesirable sound. Excessive noise may result in psychological effects such as irritability, inability to concentrate, decrease in productivity, annoyance, errors in judgment, and distraction. A noisy environment can also result in the inability to sleep, or sleep well. Elevated noise levels can affect the ability to communicate, understand what is being said, hear what is going on in the environment, degrade crew performance and operations, and create habitability concerns. Superfluous noise emissions can also create the inability to hear alarms or other important auditory cues such as an equipment malfunctioning. Recent space flight experience, evaluations of the requirements in crew habitable areas, and lessons learned (Goodman 2003; Allen and Goodman 2003; Pilkinton 2003; Grosveld et al. 2003) show the importance of maintaining an acceptable acoustics environment. This is best accomplished by having a high-quality set of limits/requirements early in the program, the "designing in" of acoustics in the development of hardware and systems, and by monitoring, testing and verifying the levels to ensure that they are acceptable.

  1. The destabilization paradox applied to friction-induced vibrations in an aircraft braking system

    Chevillot, Fabrice; Sinou, Jean-Jacques; Mazet, Guy-Bernard; Hardouin, Nicolas; Jezequel, Louis

    2008-01-01

    International audience Mechanisms of friction are known as an important source of vibrations in a large variety of engineering systems, where the emergence of oscillations is noisy and can cause severe damage to the system. The reduction or elimination of these vibrations is then an industrial issue that requires the attention of engineers and researchers together. Friction-induced vibrations have been the matter of several investigations, considering experimental, analytical, and numerica...

  2. Self-induced vibration due to upward plane jet colliding with liquid surface. Vibration mechanism of jet flutter

    When there are free liquid surface and jet or circulating flow in a vessel, sometimes the self-induced vibration of the liquid surface occurs according to the condition. The typical self-induced vibration of jet-liquid surface system is the phenomena that the upward plane jet colliding with the liquid surface causes when it is at the position partitioning the middle of a rectangular tank. There are two kinds, self-induced fluctuation and jet flutter in these phenomena. The object of this study is the latter, and it has been known that the frequency of this phenomenon coincides with that of the liquid surface vibration in a continuous tank which is partitioned at jet position and connected only near jet inflow port, and it occurs when jet velocity exceeds the limit value determined by the distance between the jet inflow port and liquid surface. The features of this phenomenon are explained. The measurement of the variable quantities, the constitution of the vibration system controlling frequency, the analysis of jet locus, the additional pressure on liquid surface by moving swell, exciting energy and the effect that various factors exert to excitation range are reported. (K.I.)

  3. Experimental investigation of the thermo-acoustic instabilities coupled with walls vibration

    Pozarlik, Artur; Kok, Jim

    2010-01-01

    In order to fulfil requirements regarding emission of harmful gases to atmosphere, the gas turbine technologies had to develop into clean techniques for energy generation. Lean premixed combustion of natural gas is one of them. Since during this process exceed of air is used, the total combustion temperature is relatively low. In consequence fewer pollutants are produced. The major drawback of this process is high sensitivity on the thermo-acoustic instabilities. Inside the combustion chamber...

  4. Measurement of vibration, flow and acoustic characteristics of a human larynx replica

    Horáček, Jaromír; Bula, Vítězslav; Radolf, Vojtěch; Vampola, T.; Dušková, Miroslava

    Brno : Brno University of Technology, 2014 - (Fuis, V.), s. 224-227 ISBN 978-80-214-4871-1. ISSN 1805-8248. [Engineering Mechanics 2014 /20./. Svratka (CZ), 12.05.2014-15.05.2014] R&D Projects: GA ČR GAP101/12/1306 Institutional support: RVO:61388998 ; RVO:61389013 Keywords : fluid-structure interaction * flutter * biomechanics of voice modeling * phonation Subject RIV: BI - Acoustics; CD - Macromolecular Chemistry (UMCH-V)

  5. Aero-Acoustic and Vibration Characteristics of Self-Oscillating Artificial Vocal Folds

    Horáček, Jaromír; Bula, Vítězslav; Radolf, Vojtěch; Vampola, T.; Dušková, M.

    Praha: Institute of Theoretical and Applied Mechanics ASCR, v. v. i, 2015 - (Náprstek, J.; Fischer, C.). s. 96-97 ISBN 978-80-86246-42-0. ISSN 1805-8248. [Engineering mechanics 2015 /21./. 11.05.2015-14.05.2015, Svratka] R&D Projects: GA ČR(CZ) GAP101/12/1306 Institutional support: RVO:61388998 Keywords : fluid-structure interaction * flutter * biomechanics of voice * modeling of phonation Subject RIV: BI - Acoustics

  6. EXPERIMENTAL STUDY OF ENHANCED HEAT TRANSFER BY FLOW-INDUCED VIBRATION OF ELASTIC TUBE BUNDLES

    2000-01-01

    A new concept of heat transfer enhancement by flow-induced vibration was put forward, and a novel heat transfer element called elastic tube bundles was designed. The experimental investigation was performed on its characteristics of flow-induced virbration in out-tube or in-tube flow. Under the conditions of fixed heat flux and steam-water heat transfer, the regularity of heat transfer enhancement by flow-induced vibration was examined.

  7. MIMO adaptive control of thruster-firing-induced vibration of satellites using multifunctional platforms

    Ma, Kougen; Ghasemi-Nejhad, Mehrdad N.

    2005-05-01

    This paper presents the concept, control strategy, and simulations of suppressing the thruster-firing-induced vibration of satellites. First, a satellite vibration reduction concept of utilizing the UHM multifunctional platform is discussed, and the structural configurations of the platform as well as the combination of the platform and a satellite are described. A satellite-like frame with the platform is analyzed, and the predominant modes of the frame are determined. A MIMO adaptive control scheme is then developed to suppress the frame vibration, and a convergence factor vector concept is introduced to ease the multi-channel convergence rate control. This controller is adjusted based on the vibration information of the frame and drives the platform to isolate the vibration transmission from the firing thruster to the satellite structure. The entire system has ten actuators: four piezoelectric stack actuators and six piezoelectric patch actuators. Eleven vibration components of the frame and platform are controlled. Nine components are in the frame for the satellite vibration suppression, and two are in the top-device plate of the platform for the thruster vibration suppression. Finally, simulations are performed to suppress the vibration of the frame for three platform positions to simulate the misalignment correction of the satellite thrust vector. The results demonstrate that the entire frame vibration at its dominant frequency decreases to 7-10% of its uncontrolled value in the three platform positions, and the thruster vibration decreases to 7.5% of its uncontrolled value.

  8. Field experiment of subgrade vibration induced by passing train in a seasonally frozen region of Daqing

    Ling Xianzhang; Zhang Feng; Zhu Zhanyuan; Ding Lin; Hu Qinli

    2009-01-01

    The vibration characteristics and attenuation of the subgrade caused by passing trains in a seasonally frozen region of Daqing, China are investigated. Three field experiments were conducted during different times through the year, in normal, freezing and thawing periods, respectively, and the influence of the season, train speed and train type, is described in this paper. The results show that: (l) the vertical component is the greatest among the three components of the measured vibration near the rail track, and as the distance to the railway track increases, the dominant vibration depends on the season. (2) Compared with the vibration in the normal period, the vertical and longitudinal vibrations increase while the lateral vibration decreases in the freezing period. However, in the thawing period, the vertical and longitudinal vibrations decrease, and the lateral vibration increases. (3) As train speeds increase, the subgrade vibration increases. (4) The vibration induced by a freight train is greater than by a passenger train. These observations provide a better understanding of the vibration and dynamic stability of the subgrade and may be useful in developing criteria for railway and building construction in cold regions.

  9. Finite-difference lattice Boltzmann simulation on acoustics-induced particle deposition

    Fu, Sau-Chung; Yuen, Wai-Tung; Wu, Chili; Chao, Christopher Yu-Hang

    2015-10-01

    Particle manipulation by acoustics has been investigated for many years. By a proper design, particle deposition can be induced by the same principle. The use of acoustics can potentially be developed into an energy-efficient technique for particle removal or filtration system as the pressure drop due to acoustic effects is low and the flow velocity is not necessary to be high. Two nonlinear acoustic effects, acoustic streaming and acoustic radiation pressure, are important. Acoustic streaming introduces vortices and stagnation points on the surface of an air duct and removes the particles by deposition. Acoustic radiation pressure causes particles to form agglomerates and enhances inertial impaction and/or gravitational sedimentation. The objective of this paper is to develop a numerical model to investigate the particle deposition induced by acoustic effects. A three-step approach is adopted and lattice Boltzamnn technique is employed as the numerical method. This is because the lattice Boltzmann equation is hyperbolic and can be solved locally, explicitly, and efficiently on parallel computers. In the first step, the acoustic field and its mean square fluctuation values are calculated. Due to the advantage of the lattice Boltzmann technique, a simple, stable and fast lattice Boltzmann method is proposed and verified. The result of the first step is input into the second step to solve for acoustic streaming. Another finite difference lattice Boltzmann method, which has been validated by a number of flows and benchmark cases in the literature, is used. The third step consists in tracking the particle's motion by a Lagrangian approach where the acoustic radiation pressure is considered. The influence of the acoustics effects on particle deposition is explained. The numerical result matches with an experiment. The model is a useful tool for optimizing the design and helps to further develop the technique.

  10. Analysis of Shear-horizontal Vibrations of Crystal Plates for Acoustic Wave Resonators and Sensors

    Liu, Bo

    2010-01-01

    In this work, theoretical analysis of shear-horizontal vibrations of crystal plates under lateral electric field excitation (LFE) without and with a fluid layer is presented. A crystal plate with separated electrodes under thickness electric field excitation (TFE) in contact with a fluid layer is also analyzed.We have started with analyzing the coupled face-shear (FS) and thickness-twist (TT) motions of piezoelectric plates with lateral electric fields, using the Mindlin's first-order theory ...

  11. Development of Design Criteria for Fluid Induced Structural Vibrations in Steam Generators and Heat Exchangers

    Flow-induced vibration in heat exchangers has been a major cause of concern in the nuclear industry for several decades. Many incidents of failure of heat exchangers due to apparent flow-induced vibration have been reported through the USNRC incident reporting system. Almost all heat exchangers have to deal with this problem during their operation. The phenomenon has been studied since the 1970s and the database of experimental studies on flow-induced vibration is constantly updated with new findings and improved design criteria for heat exchangers

  12. Self-induced vibrations of a DU96-W-180 airfoil in stall

    Skrzypinski, Witold Robert; Gaunaa, Mac; Sørensen, Niels N.;

    2014-01-01

    degrees of freedom. The computations aimed at investigating the mechanisms of both vortex-induced and stall-induced vibrations related to a wind turbine blade at standstill conditions. In this work, a DU96-W-180 airfoil was used in the angle-of-attack region potentially corresponding to stallinduced...... likely to occur at modern wind turbine blades at standstill. In contrast, the predicted cut-in wind speed necessary for the onset of stall-induced vibrations appeared high enough for such vibrations to be unlikely. Copyright © 2013 John Wiley & Sons, Ltd....

  13. Development of Design Criteria for Fluid Induced Structural Vibrations in Steam Generators and Heat Exchangers

    Uvan Catton; Vijay K. Dhir; Deepanjan Mitra; Omar Alquaddoomi; Pierangelo Adinolfi

    2004-04-06

    Flow-induced vibration in heat exchangers has been a major cause of concern in the nuclear industry for several decades. Many incidents of failure of heat exchangers due to apparent flow-induced vibration have been reported through the USNRC incident reporting system. Almost all heat exchangers have to deal with this problem during their operation. The phenomenon has been studied since the 1970s and the database of experimental studies on flow-induced vibration is constantly updated with new findings and improved design criteria for heat exchangers.

  14. Pedestrian induced vertical vibrations: Response to running using the Response Spectrum Method

    Matteoni, Giulia; Georgakis, Christos

    Footbridges are increasingly prone to vibrations and designers are generally unable to predict pedestrian-induced vertical vibrations. Many aspects of human loading are infact not properly taken into account for in the load models employed by the international codes of practice, such as the rando...

  15. Housing development near a railway tunnel: Mitigating vibration and induced noise by tweaking foundation design

    Galanti, F.M.B.; Koopman, A.

    2009-01-01

    Vibration insulation of buildings is often achieved by introducing springs in the foundation. It can be a very effective measure, especially against vibration induced noise, but also a very costly one. There is a need for less costly measures which, although less effective, may achieve the required

  16. Flow-Induced Vibrations in a Steam Blow-0ut Line of a Power Plant

    We consider in this work the large amplitude flow-induced vibrations in a steam blow-out line of a power plant. A low-order, parametrically excited, coupled nonlinear dynamical system is formulated 1iom the describing boundary value problem. Analysis of system response enables identification of governing mechanisms of: instability and complex aperiodic vibrations

  17. Analysis of fluid induced vibration of cryogenic pipes in consideration of the cooling effect

    The purpose of system analysis using fluid induced vibration is to identify the problems of the system in advance by analyzing the vibration behavior of the system excited by fluid flow. Fluid-induced vibration analysis methods, developed so far, generally use the numerical analysis method to analyze the fluid flowing inside the pipe and the infinitesimal elements at normal temperature on the basis of the governing equation obtained by applying Newton's Second Law and the momentum equation. However, as the fluid temperature changes greatly at low temperature, fluid-induced vibration analysis methods for normal temperature cannot be applied. This study investigated methods of analyzing fluid-induced vibration in consideration of the cooling effect. In consideration of the changes in the properties of the fluid and system relative to temperature, vibration behavior was analyzed numerically by means of the equation of motion. As a result, the natural frequency of the system tends to change because of the changes of the properties of materials even when the flux is constant inside the pipe, and the vibration behavior of the system was compared to that in case of normal temperature to analyze how much influence the cooling effect has on the vibration behavior of the system

  18. Selective magnetic resonance imaging of magnetic nanoparticles by Acoustically Induced Rotary Saturation (AIRS)

    Zhu, Bo; Witzel, Thomas; Jiang, Shan; Huang, Susie Y.; Rosen, Bruce R.; Wald, Lawrence L.

    2016-01-01

    Purpose We introduce a new method to selectively detect iron oxide contrast agents using an acoustic wave to perturb the spin-locked water signal in the vicinity of the magnetic particles. The acoustic drive can be externally modulated to turn the effect on and off, allowing sensitive and quantitative statistical comparison and removal of confounding image background variations. Methods We demonstrate the effect in spin-locking experiments using piezoelectric actuators to generate vibrational displacements of iron oxide samples. We observe a resonant behavior of the signal changes with respect to the acoustic frequency where iron oxide is present. We characterize the effect as a function of actuator displacement and contrast agent concentration. Results The resonant effect allows us to generate block-design “modulation response maps” indicating the contrast agent’s location, as well as positive contrast images with suppressed background signal. We show the AIRS effect stays approximately constant across acoustic frequency, and behaves monotonically over actuator displacement and contrast agent concentration. Conclusion AIRS is a promising method capable of using acoustic vibrations to modulate the contrast from iron oxide nanoparticles and thus perform selective detection of the contrast agents, potentially enabling more accurate visualization of contrast agents in clinical and research settings. PMID:25537578

  19. Proceedings of the 8. international conference on Flow-induced vibration

    of all, it proved to be efficient in solving many industrial problems, ranging from civil engineering and marine structures, aerospace terrestrial and marine transportation, to power generation and chemical processing. In the other hand, in the course of investigating the physical mechanisms responsible for FIV and the response of the structures, new mathematical and computational methods, as well as experimental and data processing techniques, have been developed which are of general interest to understand the dynamics of complex systems. Following the trend set at the last three Conferences, the 164 papers from more than 20 countries and presented in the 40 technical sessions at the FIV2004 Conference, address a large range of application areas. Major headings of the topics covered include axial flow and thin walled structures, fluid structure interaction, wind induced vibration, computational methods, flow-acoustic coupling, ship and offshore applications, bluff bodies, bio-mechanics, vortex induced vibrations, tube arrays, piping systems, gates and turbines. Among these papers, 30 have been selected for the INIS database and 35 for the ETDE database

  20. Evaluation and study on PMD performance of OPGW optical cables in wind induced vibration and galloping test environment

    Li, Jie; Zhao, Ziyuan

    2010-08-01

    This paper describes the concepts of wind induced vibration and galloping of power transmission lines, indicates the necessity of evaluation in wind induced vibration and galloping test environment, proposes the evaluation method of wind induced vibration and galloping, summarizes and analyzes the measured PMD performance data of OPGW optical fiber obtained from wind induced vibration and galloping tests on OPGW, and reaches a conclusion that the PMD performance parameters of OPGW cable stocks meet the industry standard in wind induced vibration and galloping environment, and will play an important role in project construction guidance and operation maintenance.

  1. Light-induced basilar membrane vibrations in the sensitive cochlea

    Grosh, Karl; Ren, Tianying; He, Wenxuan; Fridberger, Anders; Li, Yizeng; Nankali, Amir

    2015-12-01

    The exceptional sensitivity of mammalian hearing organ is attributed to an outer hair cell-mediated active process, where forces produced by sensory cells boost sound-induced vibrations, making soft sounds audible. This process is thought to be local, with each section of the hearing organ capable of amplifying sound-evoked movement, and nearly instantaneous, since amplification can work for sounds at frequencies up to 100 kHz in some species. To test these precepts, we developed a method for focally stimulating the living hearing organ with light. Light pulses caused intense and highly damped mechanical responses followed by traveling waves that developed with considerable delay. The delayed response was identical to movements evoked by click-like sounds. A physiologically based mathematical model shows that such waves engage the active process, enhancing hearing sensitivity. The experiments and the theoretical analysis show that the active process is neither local nor instantaneous, but requires mechanical waves traveling from the cochlear base toward its apex.

  2. Suppressing molecular vibrations in organic semiconductors by inducing strain

    Kubo, Takayoshi; Häusermann, Roger; Tsurumi, Junto; Soeda, Junshi; Okada, Yugo; Yamashita, Yu; Akamatsu, Norihisa; Shishido, Atsushi; Mitsui, Chikahiko; Okamoto, Toshihiro; Yanagisawa, Susumu; Matsui, Hiroyuki; Takeya, Jun

    2016-04-01

    Organic molecular semiconductors are solution processable, enabling the growth of large-area single-crystal semiconductors. Improving the performance of organic semiconductor devices by increasing the charge mobility is an ongoing quest, which calls for novel molecular and material design, and improved processing conditions. Here we show a method to increase the charge mobility in organic single-crystal field-effect transistors, by taking advantage of the inherent softness of organic semiconductors. We compress the crystal lattice uniaxially by bending the flexible devices, leading to an improved charge transport. The mobility increases from 9.7 to 16.5 cm2 V-1 s-1 by 70% under 3% strain. In-depth analysis indicates that compressing the crystal structure directly restricts the vibration of the molecules, thus suppresses dynamic disorder, a unique mechanism in organic semiconductors. Since strain can be easily induced during the fabrication process, we expect our method to be exploited to build high-performance organic devices.

  3. Analysis of Vortex Induced Vibrations of Marine Risers

    Karl E. Kaasen

    2003-04-01

    Full Text Available Vortex induced vibrations (VIV can be a severe problem to marine risers with regard to fatigue damage and drag loading. In order to design marine risers, therefore, it is necessary to have good theoretical and numerical models for prediction of VIV. Full-scale data are needed for verification of the models. To this end, three drilling risers were instrumented with accelerometers and rotation-rate devices for measurement of VIV. Also, sea current was measured at number of depths for reference. A large quantity of data was collected during the time the instrument system was in operation. In order to choose data records for further investigation and comparison with theoretical models the raw data had to be conditioned and converted to a suitable form. The paper describes how the riser lateral displacements were derived from the measurements. A major task has been to rid the acceleration measurements of the influence of gravity due to the riser's rotations out of the vertical and include the measurements of angular motion in a consistent way. This has been done using modal decomposition and a least-squares method combined with frequency-domain calculation to estimate the modal weights. MATLAB was used for the calculations and the presentation of results. An example of results is given.

  4. Regimes of flow induced vibration for tandem, tethered cylinders

    Nave, Gary; Stremler, Mark

    2015-11-01

    In the wake of a bluff body, there are a number of dynamic response regimes that exist for a trailing bluff body depending on spacing, structural restoring forces, and the mass-damping parameter m* ζ . For tandem cylinders with low values of m* ζ , two such regimes of motion are Gap Flow Switching and Wake Induced Vibration. In this study, we consider the dynamics of a single degree-of-freedom rigid cylinder in the wake of another in these regimes for a variety of center-to-center cylinder spacings (3-5 diameters) and Reynolds numbers (4,000-11,000). The system consists of a trailing cylinder constrained to a circular arc around a fixed leading cylinder, which, for small angle displacements, bears a close resemblance to the transversely oscillating cylinders found more commonly in existing literature. From experiments on this system, we compare and contrast the dynamic response within these two regimes. Our results show sustained oscillations in the absence of a structural restoring force in all cases, providing experimental support for the wake stiffness assumption, which is based on the mean lift toward the center line of flow.

  5. Harbor Seal Vibrissa Morphology Reduces Vortex-Induced Vibrations

    Beem, Heather; Dahl, Jason; Triantafyllou, Michael

    2011-11-01

    Studies show that harbor seals are adept at tracking small movements in the water, such as those left in the wake of fish, by using their highly sensitive whiskers to detect fluid structures, even without auditory or visual cues. The present work investigates the intriguing claim that the unique morphology of the harbor seal whisker suppresses Vortex Induced Vibrations (VIV). This implies that the geometry is specialized to reduce the background noise caused by the whisker's own wake in the detection of the upstream target. Forces on a rigid whisker model (scale: 50x) being towed steadily down a water tank while experiencing imposed oscillations are measured. A range of frequencies and amplitudes are tested, the hydrodynamic lift coefficient in phase with velocity (CL,v) is calculated for each, and values are combined in a contour plot. The region of positive CL,v peaks at an amplitude ratio of 0.1, indicating that the whisker's undulatory, asymmetric structure considerably reduces (but does not entirely suppress) regions where the structure experiences VIV in comparison with a standard cylinder, whose peak reaches an amplitude ratio of 0.8.

  6. Wind-induced Vibrations in the European Court Towers

    Hansen, Jannick B.; Brincker, Rune; Andersen, Ken G.; Andersen, Steffen; Georgakis, Christos T.

    2012-01-01

    Issues regarding occupancy comfort in vibration-sensitive structures are the motivation of this study concerning windinduced vibrations in the European Court Towers in Luxembourg. In one of the two identical towers tuned liquid dampers (TLD) have been installed. Recent studies investigate the cha...

  7. Experimental investigation of vibration, flow and acoustic characteristics of a model of human larynx

    Horáček, Jaromír; Bula, Vítězslav; Radolf, Vojtěch; Vampola, T.; Dušková, M.

    Plzeň : University of West Bohemia, 2013 - (Adámek, V.; Zajíček, M.; Jonášová, A.). s. 43-44 ISBN 978-80-261-0282-3. [Computational Mechanics 2013 /29./. 04.11.2013-06.11.2013, Špičák] R&D Projects: GA ČR GAP101/12/1306 Institutional support: RVO:61388998 Keywords : biomechanics of voice * self-oscillations * vocal folds model Subject RIV: BI - Acoustics

  8. Smartphones as experimental tools to measure acoustical and mechanical properties of vibrating rods

    González, Manuel Á.; González, Miguel Á.

    2016-07-01

    Modern smartphones have calculation and sensor capabilities that make them suitable for use as versatile and reliable measurement devices in simple teaching experiments. In this work a smartphone is used, together with low cost materials, in an experiment to measure the frequencies emitted by vibrating rods of different materials, shapes and lengths. The results obtained with the smartphone have been compared with theoretical calculations and the agreement is good. Alternatively, physics students can perform the experiment described here and use their results to determine the dependencies of the obtained frequencies on the rod characteristics. In this way they will also practice research methods that they will probably use in their professional life.

  9. Laser-induced acoustic imaging of underground objects

    Li, Wen; DiMarzio, Charles A.; McKnight, Stephen W.; Sauermann, Gerhard O.; Miller, Eric L.

    1999-02-01

    This paper introduces a new demining technique based on the photo-acoustic interaction, together with results from photo- acoustic experiments. We have buried different types of targets (metal, rubber and plastic) in different media (sand, soil and water) and imaged them by measuring reflection of acoustic waves generated by irradiation with a CO2 laser. Research has been focused on the signal acquisition and signal processing. A deconvolution method using Wiener filters is utilized in data processing. Using a uniform spatial distribution of laser pulses at the ground's surface, we obtained 3D images of buried objects. The images give us a clear representation of the shapes of the underground objects. The quality of the images depends on the mismatch of acoustic impedance of the buried objects, the bandwidth and center frequency of the acoustic sensors and the selection of filter functions.

  10. FLOW-INDUCED VIBRATION IN PIPES: CHALLENGESS AND SOLUTIONS - A REVIEW

    M. SIBA

    2016-03-01

    Full Text Available The Flow-induced vibration has recently been the topic of experimental, numerical, and theoretical studies. It was intended to implement better applications for controlling the flow using orifice technique. Having the flow under control, the orifice becomes an instrument for measuring the flow. The flow of all fluid such as water, oil, gas and vapours through an orifice was tested and mathematical models were developed adequately. The basic theme for these enormous studies was the need for the very accurate flow measurements through orifices. All experimental, theoretical, numerical, and analytical studies have agreed that there is more than one avenue to develop, modify, and enhance such measurements. However, one factor that affects the flow measurements is the vibration which was not treated as required until the mid-20th century due to enormous discoveries that damages could be rooted to vibration. Researchers have studied vibration and then proposed mathematical models in conjunction with the pressure and velocity measurements of the flowing fluids and then the effect of the vibration, induced or not induced, has been under continuous investigation. This paper is an attempt to review the previous studies regarding understanding the nature of the vibration and the possible effects of vibration on the flow and on the piping structure in order to limit the damage caused by the vibration. This study shows that the need for more experimental studies and more comprehensive analytical approaches are, in particular, very essential to develop better results.

  11. Study on thermally induced vibration of flexible boom in various thermal environments of vacuum chamber

    Kong, Changduk; Oh, Kyung-Won; Park, Hyun-Bum; Sugiyama, Y.

    2005-02-01

    In order to simulate the thermally-induced vibration phenomenon of the flexible thin boom structure of the spacecraft such as the thin solar panel and the flexible cantilever with the attached tip mass in space, the thermally-induced vibration including thermal flutter of the flexible thin boom with the concentrated tip mass was experimentally investigated at various thermal environments using a heat lamp and both vacuum and air condition using the vacuum chamber. In this experimental study, divergence speed, natural frequency and thermal strains of the thermally-induced vibration were comparatively evaluated at various thermal environment conditions. Finally the thermally-induced vibration of the flexible boom structure of the earth orbit satellite in solar radiation environment from the earth eclipse region including umbra and penumbra was simulated using the vacuum chamber and power control of the heating lamp.

  12. Raman scattering from ZnO incorporating Fe nanoparticles: Vibrational modes and low-frequency acoustic modes

    Romcevic, N., E-mail: romcevi@ipb.ac.r [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Kostic, R.; Hadzic, B.; Romcevic, M. [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Kuryliszyn-Kudelska, I.; Dobrowolski, W.D. [Institute of Physics PAS, Al. Lotnikow 32/46, 02/668 Warsaw (Poland); Narkiewicz, U.; Sibera, D. [Szcecin University of Tehnology, Institute of Chemical and Environmental Engineering, Puleskiego 10, 70-322 Szczecin, Warsaw (Poland)

    2010-10-08

    Research highlights: Nanocrystaline samples of ZnO(Fe) were synthesized by wet chemical method. Samples were characterized by X-ray diffraction to determine composition of the samples (ZnO, Fe{sub 2}O{sub 3}, ZnFe{sub 2}O{sub 4}) and the mean crystalline size (8-52 nm). Small amount (5 wt.%) of Fe{sub 2}O{sub 3} at the beginning of the synthesis results in forming of ZnFe{sub 2}O{sub 4} nanoparticles. Large amount (90 wt.%) of Fe{sub 2}O{sub 3} at the beginning of the synthesis results in forming Fe{sub 2}O{sub 3} nanoparticles. Both samples contain ZnO phase which is not registered by XRD, but is clearly seen in the Raman spectra. Main characteristics of experimental Raman spectrum in 200-1600 cm{sup -1} spectral region are: sharp peak at 436 cm{sup -1} and broad two-phonon structure at {approx}1150 cm{sup -1}, typical for ZnO; broad structure below 700 cm{sup -1} that has different position and shape in case of ZnFe{sub 2}O{sub 4} or Fe{sub 2}O{sub 3} nanoparticles. In low-frequency Raman spectra of ZnFe{sub 2}O{sub 4} nanoparticles registered peaks agree well with the calculated frequencies of acoustic phonons. As a result we identified (0,2), (0,0), (2,2) and (1,0) modes. - Abstract: Nanocrystaline samples of ZnO(Fe) were synthesized by wet chemical method. Samples were characterized by X-ray diffraction to determine composition of the samples (ZnO, Fe{sub 2}O{sub 3}, ZnFe{sub 2}O{sub 4}) and the mean crystalline size (8-52 nm). In this paper we report the experimental spectra of Raman scattering. Main characteristics of experimental Raman spectrum in 200-1600 cm{sup -1} spectral region are: sharp peak at 436 cm{sup -1} and broad two-phonon structure at {approx}1150 cm{sup -1}, typical for ZnO; broad structure below 700 cm{sup -1} that has different position and shape in case of ZnFe{sub 2}O{sub 4} or Fe{sub 2}O{sub 3} nanoparticles. Low-frequency Raman modes were measured and assigned according to confined acoustic vibrations of spherical nanoparticles

  13. Optimal Design and Acoustic Assessment of Low-Vibration Rotor Blades

    G. Bernardini

    2016-01-01

    Full Text Available An optimal procedure for the design of rotor blade that generates low vibratory hub loads in nonaxial flow conditions is presented and applied to a helicopter rotor in forward flight, a condition where vibrations and noise become severe. Blade shape and structural properties are the design parameters to be identified within a binary genetic optimization algorithm under aeroelastic stability constraint. The process exploits an aeroelastic solver that is based on a nonlinear, beam-like model, suited for the analysis of arbitrary curved-elastic-axis blades, with the introduction of a surrogate wake inflow model for the analysis of sectional aerodynamic loads. Numerical results are presented to demonstrate the capability of the proposed approach to identify low vibratory hub loads rotor blades as well as to assess the robustness of solution at off-design operating conditions. Further, the aeroacoustic assessment of the rotor configurations determined is carried out in order to examine the impact of low-vibration blade design on the emitted noise field.

  14. A stator flux oriented current vector control of a sensorless 6/4 SRM for reduction of acoustic noise and vibration

    In this paper, a stator flux oriented current vector control of a sensorless three-phase 6/4 switched reluctance motor without position sensors is presented. Space current vector control technology based on torque angle estimation was used to reduce the acoustic noise and vibration of the motor drive system. The power converter for the 6/4 switched reluctance motor is three-phase full bridge inverter. The experimental results show that the maximum level of acoustic noises and vibration are 73 dB and 8 dB; m/s/s, respectively, and the steady speed error of the drive system is less than 0.1% operated at the rated load when the drive system was operated below 1500 rpm. In addition, the transient speed performance is also satisfactory

  15. Fast reactor flow induced vibration with particular reference to PFR and conceptual CDFR design

    This paper describes development work and basic design criteria as applied to vibration induced by fluid flow for the United Kingdom LMFBR programme. Possible harmful effects that could result from excessive vibration levels are highlighted with the associated excitation mechanisms. Instances of flow-induced vibration encountered in development models and in PFR are described. Basic design requirements and the overall philosophy are considered with respect to PFR and notional CDFRs. Ongoing research objectives are outlined giving some insight into the broad strategy involved. Finally, details are given concerning projects presently in progress along with more long term proposals. (author)

  16. Study on Vibrations induced by Parametric Excitations on Strings

    Guarena, Armando Enrique León

    2007-01-01

    The present thesis work studies the parametrically excited vibrations on bridge stay cables when the natural frequency of the bridge tower is half of the resonance frequency of the cable. This condition is found at the longest stay cables of the Øresund Bridge. Experimental and numerical analysis is carried out based on a simplified scaled model (1:200) of this bridge, replacing the cables by strings made of steel. When parametrically excited vibrations are studied, certain relations between ...

  17. Railway ground vibrations induced by wheel and rail singular defects

    Kouroussis, Georges; Connolly, David P.; Alexandrou, Georgios; Vogiatzis, Konstantinos

    2015-10-01

    Railway local irregularities are a growing source of ground-borne vibration and can cause negative environmental impacts, particularly in urban areas. Therefore, this paper analyses the effect of railway track singular defects (discontinuities) on ground vibration generation and propagation. A vehicle/track/soil numerical railway model is presented, capable of accurately predicting vibration levels. The prediction model is composed of a multibody vehicle model, a flexible track model and a finite/infinite element soil model. Firstly, analysis is undertaken to assess the ability of wheel/rail contact models to accurately simulate the force generation at the wheel/rail contact, in the presence of a singular defect. It is found that, although linear contact models are sufficient for modelling ground vibration on smooth tracks, when singular defects are present higher accuracy wheel/rail models are required. Furthermore, it is found that the variation in wheel/rail force during the singular defect contact depends on the track flexibility, and thus requires a fully coupled vehicle/track/foundation model. Next, a parametric study of ground vibrations generated by singular rail and wheel defects is undertaken. Six shapes of discontinuity are modelled, representing various defect types such as transition zones, switches, crossings, rail joints and wheel flats. The vehicle is modelled as an AM96 train set and it is found that ground vibration levels are highly sensitive to defect height, length and shape.

  18. Acoustic Resonance Frequency Elimination Device for Safety Relief Valves

    Industry experience has shown that Safety Relief Valves (SRVs) and Steam Dryers installed in Boiling Water Reactors (BWRs) experience vibration induced degradation and failures caused by acoustic resonance vibration of the main steam lines, resulting in decreased reliability and potential safety issues. The resonance is caused by vortex shedding from the standpipe inlet and acoustic standing waves in the standpipe, occurring when the two frequencies match. (Author)

  19. The postural disorientation induced by neck muscle vibration subsides on lightly touching a stationary surface or aiming at it.

    Bove, M; Bonzano, L; Trompetto, C; Abbruzzese, G; Schieppati, M

    2006-12-28

    The aim of this study was to investigate whether the standing body spatial disorientation, induced by neck muscle vibration, and the related post-effects can be suppressed by light finger touch (LFT) of a stationary surface. Continuous (60 s) vibration of dorsal neck or sternocleidomastoid muscle was administered with eyes closed. The center of foot pressure (CFP) displacement, measured by a stabilometric platform, indicated the degree of vibration-induced body tilt. We also investigated whether sensory information from LFT itself was necessary or anticipation of a more secure posture was enough for reducing vibration effects. To this aim, we administered a vibration pulse (5 s) to dorsal neck or sternocleidomastoid muscle and during reaching to the stationary surface. CFP was recorded during both vibration and post-vibration condition and during the aiming task. Neck vibration induced significant CFP displacement in the direction opposite to vibration site. Post-vibration, CFP slowly returned to control values with ample oscillations. LFT during vibration reduced body tilt. LFT was more effective when fingertip contact was in the plane of the greatest tilt. LFT applied during either vibration or post-vibration period reduced post-vibration effects. Reaching toward the stationary surface was enough for reducing vibration-induced body tilt to values close to those observed during actual LFT. The novel conclusions of this study are: 1) LFT is able to relieve the effects of vibration-induced abnormal proprioceptive input from the neck, a segment central to postural control and orientation; 2) LFT during vibration also attenuates vibration post-effects, further suggesting that its action is not merely mechanical; 3) the intention to stabilize the body generates a new postural 'set' sufficient for diminishing body tilt. PMID:17071008

  20. Investigation of vibration of the heating cylindrical rod induced by boiling and condensation phenomena

    Flow induced vibrations (FIVs) are important and interesting phenomena from the view point of reactor safety. In nuclear power plants, fuel pins in reactor cores, heat exchange tubes in steam generators and some other complex structures can cause FIVs. Especially, in Boiling Water Reactor, subcooled or saturated boiling flows induce vibrations. These vibrations result in fretting wear of the structures and may cause a radioactive leakage. This paper deals with an experimental investigation of the cylindrical rod's vibrations induced from boiling an condensation phenomena on the circumferential surface of itself. The measurements were conducted changing the bulk water temperature from the saturation temperature at an atmospheric pressure to the degree of subcooling up to around 30 K. (author)

  1. Flow-induced vibration for light water reactors. Program final report

    The Flow-Induced Vibrations for Light Water Reactors Program was a five-year effort to develop basic knowledge and understanding needed to improve the flow-induced vibration design of light water reactors. Major tasks included analytical and test investigations of the flow-induced vibration of cylinders in isolation and arrays in smooth and turbulent single-vibration testing of reactor components including reactor inlet plenum components, jet pumps, low-pressure coolant injection coupling, and fuel rods. Cases of self-excited limit cycle response were encountered which required design modifications. The fuel rod tests were made in axially flowing water and steam/water mixtures under adiabatic and boiling conditions

  2. Flow Induced Acoustic Resonance in In-line Tube Banks

    Hiromitsu Hamakawa; Tohru Fukano; Eiichi Nishida; Yoshikazu Satou

    2006-01-01

    In the present paper the attention is focused on the relation between vortex shedding phenomena and acoustic resonance which occurred in the two-dimensional model of boiler. There were tube banks with in-line arrangement for small tube pitch ratio. We measured the sound pressure level, the phase delay of acoustic pressures, the spectrum of velocity fluctuation and the gap velocity. As a result, we found two peak frequencies of sound pressure level with different Strouhal numbers St, mainly about 0.26 and 0.52. The noise of St=0.26 was the resonance of transverse mode and St=0.52 was longitudinal mode. The vortex shedding of St=0.15 was generated inside the tube banks without acoustic resonance. As gap velocity increased, we observed that the peak level of spectrum was weak and broad-banded. The onset velocity of the acoustic resonance of longitudinal mode was lower than that of transverse mode.

  3. The Effects of Acute Stress-Induced Sleep Disturbance on Acoustic Trauma-Induced Tinnitus in Rats

    Stiles, Lucy; Darlington, Cynthia L.; Smith, Paul F.

    2014-01-01

    Chronic tinnitus is a debilitating condition and often accompanied by anxiety, depression, and sleep disturbance. It has been suggested that sleep disturbance, such as insomnia, may be a risk factor/predictor for tinnitus-related distress and the two conditions may share common neurobiological mechanisms. This study investigated whether acute stress-induced sleep disturbance could increase the susceptibility to acoustic trauma-induced tinnitus in rats. The animals were exposed to unilateral acoustic trauma 24 h before sleep disturbance being induced using the cage exchange method. Tinnitus perception was assessed behaviourally using a conditioned lick suppression paradigm 3 weeks after the acoustic trauma. Changes in the orexin system in the hypothalamus, which plays an important role in maintaining long-lasting arousal, were also examined using immunohistochemistry. Cage exchange resulted in a significant reduction in the number of sleep episodes and acoustic trauma-induced tinnitus with acoustic features similar to a 32 kHz tone at 100 dB. However, sleep disturbance did not exacerbate the perception of tinnitus in rats. Neither tinnitus alone nor tinnitus plus sleep disturbance altered the number of orexin-expressing neurons. The results suggest that acute sleep disturbance does not cause long-term changes in the number of orexin neurons and does not change the perception of tinnitus induced by acoustic trauma in rats. PMID:25162023

  4. Coriolis induced vibration and rotation mixing in formaldehyde

    The effect of Coriolis interaction on the intramolecular dynamics of formaldehyde is investigated theoretically. Classical dynamics calculations are presented that include all seven degrees of freedom, i.e., the six vibrational modes and the rotational mode associated with K, the projection of total angular momentum on a body-fixed axis. These calculations show that vibrational modes 4 (out of plane bend) and 6 (HCO bend) can be significantly coupled due to Coriolis interaction. The qualitative features of such coupling is further understood via study of a reduced dimension model that includes just modes 4, 6, and the rotational degree of freedom. Two interesting classical consequences of Coriolis interaction are noted. First, for large K (e.g., for chemical bondKchemical bond/similar to/J) we find vibrational mixing can occur without significant deterioration of K. We find that this mixing is not due to the usual ''Chirikov'' or pendulum picture of nonlinear resonance. Second, we find that both vibrational and rotational mixing can occur when the rotational frequency is in resonance with the difference in vibrational frequencies. In this situation, the resonances lead to a partial K mixing. Chaos about the resonances can lead to a more extensive K mixing. Quantum calculations are also performed for the reduced dimension model and the nature of the quantum eigenstates is discussed in relation to the corresponding classical dynamics

  5. Control of wind-induced vibration of long-span bridges and tall buildings

    GU Ming

    2007-01-01

    With the rapid increase in scales of structures,research on controlling wind-induced vibration of large-scale structures,such as long-span bridges and super-tall buildings,has been an issue of great concern.For wind-induced vibration of large-scale structures,vibration frequencies and damping modes vary with wind speed.Passive,semiactive,and active control strategies are developed to improve the windresistance performance of the structures in this paper.The multiple tuned mass damper (MTMD) system is applied to control vertical bending buffeting response.A new semiactive lever-type tuned mass damper (TMD) with an adjustable frequency is proposed to control vertical bending buffeting and torsional buffeting and flutter in the whole velocity range of bridge decks.A control strategy named sinusoidal reference strategy is developed for adaptive control of wind-induced vibration of super-tall buildings.Multiple degrees of freedom general building aeroelastic model with a square cross-section is tested in a wind tunnel.The results demonstrate that the proposed strategies can reduce vibration effectively,and can adapt to wind-induced vibration control of large-scale structures in the uncertain dynamic circumstance.

  6. Application of inertia-induced excitation theory for nonlinear acoustic modes in colloidal plasma equilibrium flow

    P K Karmakar

    2007-04-01

    Application of inertia-induced acoustic excitation theory offers a new resonant excitation source channel of acoustic turbulence in the transonic domain of plasma flow. In bi-ion plasmas like colloidal plasma, two well-defined transonic points exist corresponding to the parent ion and the dust grain-associated acoustic modes. As usual, the modified ion acoustic mode (also known as dust ion-acoustic (DIA) wave) dynamics associated with parent ion inertia is excitable for both nanoscale- and micronscale-sized dust grains. It is found that the so-called (ion) acoustic mode (also known as dust-acoustic (DA) wave) associated with nanoscale dust grain inertia is indeed resonantly excitable through the active role of weak but finite parent ion inertia. It is interestingly conjectured that the same excitation physics, as in the case of normal plasma sound mode, operates through the active inertial role of plasma thermal species. Details of the nonlinear acoustic mode analyses of current interest in transonic domains of such impure plasmas in hydrodynamic flow are presented.

  7. Numerical simulation of flow induced airfoil vibrations with large amplitudes

    Sváček, Petr; Feistauer, M.; Horáček, Jaromír

    2007-01-01

    Roč. 23, - (2007), s. 391-411. ISSN 0889-9746 R&D Projects: GA AV ČR IAA200760613 Institutional research plan: CEZ:AV0Z20760514 Keywords : aeroelasticity * flutter * nonlinear oscillations Subject RIV: BI - Acoustics Impact factor: 0.821, year: 2007

  8. Numerical simulation of flow induced airfoil vibrations with large amplitudes

    Sváček, P.; Feistauer, M.; Horáček, Jaromír

    2005-01-01

    Roč. 2005, č. 1 (2005), s. 1-30 R&D Projects: GA ČR(CZ) GA101/02/0391 Institutional research plan: CEZ:AV0Z20760514 Keywords : aeroelasticity * flutter * finite element method Subject RIV: BI - Acoustics

  9. Vibration-Induced Conductivity Fluctuation Measurement for Soil Bulk Density Analysis

    Kishne, Andrea Sz; Chang, Hung-Chih; Kish, Laszlo B

    2007-01-01

    Soil bulk density affects water storage, water and nutrient movement, and plant root activity in the soil profile. Its measurement is difficult in field conditions. Vibration-induced conductivity fluctuation was investigated to quantify soil bulk density with possible field applications in the future. The AC electrical conductivity of soil was measured using a pair of blade-like electrodes while exposing the soil to periodic vibration. The blades were positioned longitudinally and transversally to the direction of the induced vibration to enable the calculation of a normalized index. The normalized index was expected to provide data independent from the vibration strength and to reduce the effect of soil salinity and water content. The experiment was conducted on natural and salinized fine sand at two moisture conditions and four bulk densities. The blade-shaped electrodes improved electrode-soil contact compared to cylindrical electrodes, and thereby, reduced measurement noise. Simulations on a simplified re...

  10. Computational insights into intriguing vibration-induced pulsing diradical character in perfluoropentacene and the perfluorination effect.

    Zhang, Fengying; Feng, Yiwei; Song, Xinyu; Bu, Yuxiang

    2016-06-28

    As an n-type organic semiconductor compound, perfluoropentacene has more widespread applications in organic electronics because of its higher electron mobility compared with its parent pentacene. Herein, we explore intriguing dynamic electronic properties of perfluoropentacene caused by structural vibrations using density functional theory calculations. Perfluoropentacene could exhibit diradical character because of the persistent vibrations, although it belongs to a closed-shell singlet molecule in its equilibrium configuration. Not all the vibration-induced structural changes can induce diradical character, but only those leading to a small singlet-triplet energy gap, especially the small HOMO-LUMO gap, as well as the short cross-linking C-C bonds and distorted carbon ring structures in polyacetylene chains make great contributions. Due to molecular vibrations, the diradical character of dynamic perfluoropentacene exhibits pulsing behavior. Compared with pentacene, its perfluorination can not only considerably stabilize two frontier molecular orbitals, but also reduce the HOMO-LUMO gap, thus leading to an increase of the number of vibrational modes which can make the diradical character appear. In particular, perfluorination makes 19 diradical vibrational modes appear in the low frequency region. These observations indicate that some low energy pulses can trigger perfluoropentacene molecular vibrations according to some low energy modes and thus the appearance of pulsing diradical character or molecular magnetism. Clearly, the observed novel characters of a molecule possessing hidden pulsing diradical character and tunable magnetism in this work would contribute to opening up promising areas for designing peculiar magnetic materials. PMID:27250923

  11. Experimental Investigation on Flow-Induced Vibration of Fuel Rods in Supercritical Water Loop

    Licun Wu

    2014-01-01

    Full Text Available The supercritical water-cooled reactor (SCWR is one of the most promising Generation IV reactors. In order to make the fuel qualification test for SCWR, a research plan is proposed to test a small scale fuel assembly in a supercritical water loop. To ensure the structure safety of fuel assembly in the loop, a flow-induced vibration experiment was carried out to investigate the vibration behavior of fuel rods, especially the vibration caused by leakage flow. From the experiment result, it can be found that: the vibration of rods is mainly caused by turbulence when flow rate is low. However, the effects of leakage flow become obvious as flow rate increases, which could changes the distribution of vibrational energy in spectrum, increasing the vibrational energy in high-frequency band. That is detrimental to the structure safety of fuel rods. Therefore, it is more reasonable to improve the design by using the spacers with blind hole, which can eliminate the leakage flow, to assemble the fuel rods in supercritical water loop. On the other hand, the experimental result could provide a benchmark for the theoretical studies to validate the applicability of boundary condition set for the leakage-flow-induced vibration.

  12. Incorporating a disturbance observer with direct velocity feedback for control of human-induced vibrations

    Nyawako, Donald; Reynolds, Paul; Hudson, Emma

    2016-04-01

    Feedback control strategies are desirable for disturbance rejection of human-induced vibrations in civil engineering structures as human walking forces cannot easily be measured. In relation to human-induced vibration control studies, most past researches have focused on floors and footbridges and the widely used linear controller implemented in the trials has been the direct velocity feedback (DVF) scheme. With appropriate compensation to enhance its robustness, it has been shown to be effective at damping out the problematic modes of vibration of the structures in which the active vibration control systems have been implemented. The work presented here introduces a disturbance observer (DOB) that is used with an outer-loop DVF controller. Results of analytical studies presented in this work based on the dynamic properties of a walkway bridge structure demonstrate the potential of this approach for enhancing the vibration mitigation performance offered by a purely DVF controller. For example, estimates of controlled frequency response functions indicate improved attenuation of vibration around the dominant frequency of the walkway bridge structure as well as at higher resonant frequencies. Controlled responses from three synthesized walking excitation forces on a walkway bridge structure model show that the inclusion of the disturbance observer with an outer loop DVF has potential to improve on the vibration mitigation performance by about 3.5% at resonance and 6-10% off-resonance. These are realised with hard constraints being imposed on the low frequency actuator displacements.

  13. Theoretical study of time-dependent, ultrasound-induced acoustic streaming in microchannels

    Muller, Peter Barkholt; Bruus, Henrik

    2015-12-01

    Based on first- and second-order perturbation theory, we present a numerical study of the temporal buildup and decay of unsteady acoustic fields and acoustic streaming flows actuated by vibrating walls in the transverse cross-sectional plane of a long straight microchannel under adiabatic conditions and assuming temperature-independent material parameters. The unsteady streaming flow is obtained by averaging the time-dependent velocity field over one oscillation period, and as time increases, it is shown to converge towards the well-known steady time-averaged solution calculated in the frequency domain. Scaling analysis reveals that the acoustic resonance builds up much faster than the acoustic streaming, implying that the radiation force may dominate over the drag force from streaming even for small particles. However, our numerical time-dependent analysis indicates that pulsed actuation does not reduce streaming significantly due to its slow decay. Our analysis also shows that for an acoustic resonance with a quality factor Q , the amplitude of the oscillating second-order velocity component is Q times larger than the usual second-order steady time-averaged velocity component. Consequently, the well-known criterion v1≪cs for the validity of the perturbation expansion is replaced by the more restrictive criterion v1≪cs/Q . Our numerical model is available as supplemental material in the form of comsol model files and matlab scripts.

  14. Laser-induced acoustic wave generation/propagation/interaction in water in various internal channels

    Ko, Seung Hwan; Lee, Daeho; Pan, Heng; Ryu, Sang-Gil; Grigoropoulos, Costas P.; Kladias, Nick; Panides, Elias; Domoto, Gerald A.

    2010-01-01

    Short pulsed laser-induced single acoustic wave generation, propagation, interaction within a water-filled internal channel are experimentally and numerically studied. A large-area, short-duration, single-plane acoustic wave was generated by the thermoelastic interaction of a homogenized nanosecond pulsed laser beam with a liquid–solid interface and propagated at the speed of sound in water. Laser flash Schlieren photography was used to visualize the transient interaction of the plane acousti...

  15. Enhanced acoustic cavitation following laser-induced bubble formation : long-term memory effect

    Yavaṣ, Oğuz; Leiderer, Paul; Park, Hee K.; Grigoropoulos, Costas P.; Poon, Chie C.; Tam, Andrew C.

    1994-01-01

    The enhancement of acoustic caviation at a liquid-solid interface following laser-induced bubble formation is studied. The experiment results indicate that metastable ultramicroscopic bubbles formed on the solid surface cause a long-term memory effect on acoustic cavitation. By performing a double-pulse experiment using two excimer lasers, the temporal decay of this memory effect is determined for two different liquids on a chromium surface. An explanation of the observed decay mode by a ...

  16. Vibration-induced jitter control in satellite optical communication

    Xue, Zheng-yan; Qi, Bo; Ren, Ge

    2013-08-01

    Laser satellite communication has become especially attractive in recent years. However, because the laser beam is very narrow and there is a long distance between satellites, the laser communication channel is very sensitive to vibrations of the optical platform. These vibrations cause optical jitter, leading to the reduction of received signals and bit-error rate degradation. Consequently, optical jitter control with PAT (pointing acquisition and tracking) subsystems is a critical problem in laser satellite communication. To compensate for the platform vibration effectively in realtime, in this paper, an adaptive feedback control technique based on Youla-parameterization is presented, which can adapt to the current disturbance acting on the laser beam by adjusting its parameters in realtime to maintain optimal performance. The main idea is to use the well-known Youla parameterization formula to construct a feedback control scheme with the guaranteed closed loop stability, and the feedback controller is a function of plant coprime factors and a free parameter Q. For adaptive disturbance estimation, the free parameter Q is set to an adaptive finite impulse response (FIR) filter, the coefficients of which are updated by a recursive least-squares (RLS) algorithm in realtime. It is shown in experiment that the adaptive feedback control technique based on Youla-parameterization can reject the optical jitter caused by satellite platform vibration effectively and improve the performance of the system.

  17. Train induced vibrations in geosynthetic reinforced railway embankments

    Zania, Varvara; Hededal, Ole; Krogsbøll, Anette

    2011-01-01

    High–speed trains may generate ground vibrations which cause undesirable environmental and economical impacts such as nuisance of the passengers, deflections along the rail, and possibly impairment of the stability of the embankments. The increase of the velocity of a moving load on homogeneous...

  18. A simple model to predict train-induced vibration: theoretical formulation and experimental validation

    No suitable handy tool is available to predict train-induced vibration on environmental impact assessment. A simple prediction model is proposed which has been calibrated for high speed trains. The model input data are train characteristics, train speed and track properties; model output data are soil time-averaged velocity and velocity level. Model results have been compared with numerous vibration data retrieved from measurement campaigns led along the most important high-speed European rail tracks. Model performances have been tested by comparing measured and predicted vibration values

  19. The Torsional Vibration of Turbo Axis Induced by Unsteady Aerodynamic Force on Rotor blade

    ChenZuoyi; WuXiaofeng

    1998-01-01

    An algorithm for computing the 3-D oscillating flow field of the balde passage under the torsional vibration of the rotor is applied to analyze the stability in turbomachines.The induced flow field responding to blade vibration is computed by Oscillating Fluid Mechanics Method and parametric Polynomial Method.After getting the solution of the unsteady flow field,the work done by the unsteay aerodynamic force acting on the blade can be obtained.The negative or positive work is the criterion of the aeroelastic stability.Numerical results indicate that there are instabilities of the torsional vibration in some frequency bands.

  20. Vortex-induced vibration of a square-section cylinder with incidence angle variation

    Zhao, Jisheng; Nemes, Andras; Lo Jacono, David; Sheridan, John

    2010-01-01

    Vortex-induced vibration (VIV) occurs when vortex shedding from a body results in fluctuating forces that, in turn, cause the body to vibrate. This can result in undesired large-amplitude vibrations leading to structural damage or catastrophic failure. While much has been done on the VIV of a circular cylinder less has been done on other canonical bluff bodies, such as rectangular cylinders. The present experimental work studied the VIV of a square cross-section cylinder in a water channel, w...

  1. Interference-induced angle-independent acoustical transparency

    It is revealed that the Fano-like interference leads to the extraordinary acoustic transmission through a slab metamaterial of thickness much smaller than the wavelength, with each unit cell consisting of a Helmholtz resonator and a narrow subwavelength slit. More importantly, both the theoretical analysis and experimental measurement show that the angle-independent acoustical transparency can be realized by grafting a Helmholtz resonator and a quarter-wave resonator to the wall of a narrow subwavelength slit in each unit cell of a slit array. The observed phenomenon results from the interferences between the waves propagating in the slit, those re-radiated by the Helmholtz resonator, and those re-radiated by the quarter-wave resonator. The proposed design may find its applications in designing angle-independent acoustical filters and controlling the phase of the transmitted waves

  2. Interference-induced angle-independent acoustical transparency

    Qi, Lehua; Yu, Gaokun, E-mail: gkyu@ouc.edu.cn; Wang, Ning [Department of Marine Technology, Ocean University of China, Qingdao 266100 (China); Wang, Xinlong [Key Laboratory of Modern Acoustics and Institute of Acoustics, Nanjing University, Nanjing 210093 (China); Wang, Guibo [Shipbuilding Information Center of China, Beijing 100012 (China)

    2014-12-21

    It is revealed that the Fano-like interference leads to the extraordinary acoustic transmission through a slab metamaterial of thickness much smaller than the wavelength, with each unit cell consisting of a Helmholtz resonator and a narrow subwavelength slit. More importantly, both the theoretical analysis and experimental measurement show that the angle-independent acoustical transparency can be realized by grafting a Helmholtz resonator and a quarter-wave resonator to the wall of a narrow subwavelength slit in each unit cell of a slit array. The observed phenomenon results from the interferences between the waves propagating in the slit, those re-radiated by the Helmholtz resonator, and those re-radiated by the quarter-wave resonator. The proposed design may find its applications in designing angle-independent acoustical filters and controlling the phase of the transmitted waves.

  3. Action spectroscopy for single-molecule motion induced by vibrational excitation with a scanning tunneling microscope

    Ueba, H.; Persson, B.N.J.

    2007-01-01

    We propose an action spectroscopy for single-molecule motion induced by vibrational excitation with a scanning tunneling microscope (STM). Calculations of the inelastic tunneling current for excitation of the C-O stretch mode of the CO molecule on metal surfaces are combined with a theory which describes how the energy in the vibrational mode is transferred to a reaction coordinate mode to overcome the activation barrier. The calculated rate for CO hopping on Pd (110) as a function of the bia...

  4. Robust saturated control of human-induced floor vibrations via a proof-mass actuator

    Diaz, I.M.; Reynolds, P.

    2009-01-01

    This paper is concerned with the design of a robust active vibration control system that makes use of a proof-mass actuator for the mitigation of human-induced vibrations in floor structures. Ideally, velocity feedback control (VFC) is unconditionally stable and robust to spillover effects, interlacing of poles and zeros of collocated control is then accomplished. However, the use of a proof-mass actuator influences the system dynamics and the alternating pole-zero pattern of the system forme...

  5. Vibrational wave packet induced oscillations in two-dimensional electronic spectra. I. Experiments

    Nemeth, Alexandra; Milota, Franz; Mancal, Tomas; Lukes, Vladimir; Hauer, Juergen; Kauffmann, Harald F.; Sperling, Jaroslaw

    2010-01-01

    This is the first in a series of two papers investigating the effect of electron-phonon coupling in two-dimensional Fourier transformed electronic spectroscopy. We present a series of one- and two-dimensional nonlinear spectroscopic techniques for studying a dye molecule in solution. Ultrafast laser pulse excitation of an electronic transition coupled to vibrational modes induces a propagating vibrational wave packet that manifests itself in oscillating signal intensities and line-shapes. For...

  6. Flow-induced vibrations of two tandem cylinders in a channel

    Jiang Ren-Jie

    2012-01-01

    We numerically studied flow-induced vibrations of two tandem cylinders in transverse direction between two parallel walls. The effect of the horizontal separation between two cylinders, ranging from 1.1 to 10, on the motions of the cylinders and the flow structures were investigated and a variety of periodic and non-periodic vibration regimes were observed. The results show that when two cylinders are placed in close proximity to each other, compared with the case of an isolated cylinde...

  7. Texture-induced vibrations in the forearm during tactile exploration

    Delhaye, Benoit; Hayward, Vincent; Lefèvre, Philippe; Thonnard, Jean-Louis

    2012-01-01

    Humans can detect and discriminate between fine variations of surface roughness using active touch. It is hitherto believed that roughness perception is mediated mostly by cutaneous and subcutaneous afferents located in the fingertips. However, recent findings have shown that following abolishment of cutaneous afferences resulting from trauma or pharmacological intervention, the ability of subjects to discriminate between textures roughness was not significantly altered. These findings suggest that the somatosensory system is able to collect textural information from other sources than fingertip afference. It follows that signals resulting of the interaction of a finger with a rough surface must be transmitted to stimulate receptor populations in regions far away from the contact. This transmission was characterized by measuring in the wrist vibrations originating at the fingertip and thus propagating through the finger, the hand and the wrist during active exploration of textured surfaces. The spectral analysis of the vibrations taking place in the forearm tissues revealed regularities that were correlated with the scanned surface and the speed of exploration. In the case of periodic textures, the vibration signal contained a fundamental frequency component corresponding to the finger velocity divided by the spatial period of the stimulus. This regularity was found for a wide range of textural length scales and scanning velocities. For non-periodic textures, the spectrum of the vibration did not contain obvious features that would enable discrimination between the different stimuli. However, for both periodic and non-periodic stimuli, the intensity of the vibrations could be related to the microgeometry of the scanned surfaces. PMID:22783177

  8. Stochastic Response of Energy Balanced Model for Vortex-Induced Vibration

    Nielsen, Søren R.K.; Krenk, S.

    A double oscillator model for vortex-induced oscillations of structural elements based on exact power exchange between fluid and structure, recently proposed by authors, is extended to include the effect of the turbulent component of the wind. In non-turbulent flow vortex-induced vibrations of li...

  9. Thermally induced vibration of composite solar array with honeycomb panels in low earth orbit

    Solar arrays are critical appendages that provide primary power sources for spacecrafts. This paper presents a numerical method to characterize the thermal response of a composite solar array subjected to space heat flux. Thermally induced vibration is investigated based on this method. The thermally induced vibrations of a solar array using two commonly used materials are also compared. Thermally induced vibrations in different thermal environments, incident angles of solar radiation, and material properties of honeycomb panel are discussed to reveal the causes of thermally induced vibration. Simulation results reveal the dynamic response of the solar array in low earth orbit under transient temperature, which could provide guidance for designers to optimize the structure utilized in minimizing the influence of the space thermal environment. - Highlights: • A method to characterize the thermal response of a rigid solar array is presented. • Composite material and orbital thermal environments are considered in the model. • Thermally induced vibration is investigated based on this model. • The effects of different parameters are discussed. • Incident angle and parameters of honeycomb composite have significant influence

  10. Numerical Approximation of Flow Induced Vibration of Vocal Folds

    Sváček, P.; Horáček, Jaromír

    Berlin : Springer, 2011 - (Clavero, C.; Gracia, J.; Lisbona, F.), s. 227-234 ISBN 978-3-642-19664-5. ISSN 1439-7358. [BAIL 2010. Zaragoza (ES), 05.07.2010-09.07.2010] R&D Projects: GA MŠk OC09019 Institutional research plan: CEZ:AV0Z20760514 Keywords : FEM * fluid-structure interaction * biomechanics of voice Subject RIV: BI - Acoustics

  11. Numerical modelling of flow induced airfoil vibrations problem

    Sváček, Petr; Feistauer, M.; Horáček, Jaromír

    Queen´s University Belfast: CEIAT, Queen´s University Belfast, Nothern Ireland, 2005, s. 1-10. [International Conference on Innovation and Integration in Aerospace Sciences /1./. Queen´s University Belfast (GB), 04.04.2004-05.04.2004] R&D Projects: GA MPO(CZ) FT-TA/026 Institutional research plan: CEZ:AV0Z20760514 Keywords : unsteady viscous flows * aeroelasticity * flutter Subject RIV: BI - Acoustics

  12. Sympathetic Tone Induced by High Acoustic Tempo Requires Fast Respiration.

    Watanabe, Ken; Ooishi, Yuuki; Kashino, Makio

    2015-01-01

    Many studies have revealed the influences of music, and particularly its tempo, on the autonomic nervous system (ANS) and respiration patterns. Since there is the interaction between the ANS and the respiratory system, namely sympatho-respiratory coupling, it is possible that the effect of musical tempo on the ANS is modulated by the respiratory system. Therefore, we investigated the effects of the relationship between musical tempo and respiratory rate on the ANS. Fifty-two healthy people aged 18-35 years participated in this study. Their respiratory rates were controlled by using a silent electronic metronome and they listened to simple drum sounds with a constant tempo. We varied the respiratory rate-acoustic tempo combination. The respiratory rate was controlled at 15 or 20 cycles per minute (CPM) and the acoustic tempo was 60 or 80 beats per minute (BPM) or the environment was silent. Electrocardiograms and an elastic chest band were used to measure the heart rate and respiratory rate, respectively. The mean heart rate and heart rate variability (HRV) were regarded as indices of ANS activity. We observed a significant increase in the mean heart rate and the low (0.04-0.15 Hz) to high (0.15-0.40 Hz) frequency ratio of HRV, only when the respiratory rate was controlled at 20 CPM and the acoustic tempo was 80 BPM. We suggest that the effect of acoustic tempo on the sympathetic tone is modulated by the respiratory system. PMID:26284521

  13. Sympathetic Tone Induced by High Acoustic Tempo Requires Fast Respiration.

    Ken Watanabe

    Full Text Available Many studies have revealed the influences of music, and particularly its tempo, on the autonomic nervous system (ANS and respiration patterns. Since there is the interaction between the ANS and the respiratory system, namely sympatho-respiratory coupling, it is possible that the effect of musical tempo on the ANS is modulated by the respiratory system. Therefore, we investigated the effects of the relationship between musical tempo and respiratory rate on the ANS. Fifty-two healthy people aged 18-35 years participated in this study. Their respiratory rates were controlled by using a silent electronic metronome and they listened to simple drum sounds with a constant tempo. We varied the respiratory rate-acoustic tempo combination. The respiratory rate was controlled at 15 or 20 cycles per minute (CPM and the acoustic tempo was 60 or 80 beats per minute (BPM or the environment was silent. Electrocardiograms and an elastic chest band were used to measure the heart rate and respiratory rate, respectively. The mean heart rate and heart rate variability (HRV were regarded as indices of ANS activity. We observed a significant increase in the mean heart rate and the low (0.04-0.15 Hz to high (0.15-0.40 Hz frequency ratio of HRV, only when the respiratory rate was controlled at 20 CPM and the acoustic tempo was 80 BPM. We suggest that the effect of acoustic tempo on the sympathetic tone is modulated by the respiratory system.

  14. STUDY ON VIBRATION SENSITIVITY DIFFERENT BODY AREAS IN PATIENTS WITH VIBRATION-INDUCER DISEASES EXPOSED TO A LOCAL VIBRATION AND IN PATIENTS WITH AN OCCUPATIONAL NEUROSENSORIC DULLNESS OF HEARING

    Kartapoltseva, N.

    2008-01-01

    The pathological disorders in the state of the peripheral nerves based on the data of the vibration sensitivity studies were observed to be in both the patients with the vibration-induced diseases as a result of the local vibration exposure and in the patients with an occupational neurosensoric dullness of hearing. This may assume a total effect mechanism of the physical factors on the human organism. In the former case the alterations observedshowed a more pronounced character.

  15. Capabilities, Design, Construction and Commissioning of New Vibration, Acoustic, and Electromagnetic Capabilities Added to the World's Largest Thermal Vacuum Chamber at NASA's Space Power Facility

    Motil, Susan M.; Ludwiczak, Damian R.; Carek, Gerald A.; Sorge, Richard N.; Free, James M.; Cikanek, Harry A., III

    2011-01-01

    NASA s human space exploration plans developed under the Exploration System Architecture Studies in 2005 included a Crew Exploration Vehicle launched on an Ares I launch vehicle. The mass of the Crew Exploration Vehicle and trajectory of the Ares I coupled with the need to be able to abort across a large percentage of the trajectory generated unprecedented testing requirements. A future lunar lander added to projected test requirements. In 2006, the basic test plan for Orion was developed. It included several types of environment tests typical of spacecraft development programs. These included thermal-vacuum, electromagnetic interference, mechanical vibration, and acoustic tests. Because of the size of the vehicle and unprecedented acoustics, NASA conducted an extensive assessment of options for testing, and as result, chose to augment the Space Power Facility at NASA Plum Brook Station, of the John H. Glenn Research Center to provide the needed test capabilities. The augmentation included designing and building the World s highest mass capable vibration table, the highest power large acoustic chamber, and adaptation of the existing World s largest thermal vacuum chamber as a reverberant electromagnetic interference test chamber. These augmentations were accomplished from 2007 through early 2011. Acceptance testing began in Spring 2011 and will be completed in the Fall of 2011. This paper provides an overview of the capabilities, design, construction and acceptance of this extraordinary facility.

  16. Acoustically enhanced heat transport

    Ang, Kar M.; Hung, Yew Mun; Tan, Ming K., E-mail: tan.ming.kwang@monash.edu [School of Engineering, Monash University Malaysia, 47500 Bandar Sunway, Selangor (Malaysia); Yeo, Leslie Y. [Micro/Nanophysics Research Laboratory, RMIT University, Melbourne, VIC 3001 (Australia); Friend, James R. [Department of Mechanical and Aerospace Engineering, University of California, San Diego, California 92093 (United States)

    2016-01-15

    We investigate the enhancement of heat transfer in the nucleate boiling regime by inducing high frequency acoustic waves (f ∼ 10{sup 6} Hz) on the heated surface. In the experiments, liquid droplets (deionized water) are dispensed directly onto a heated, vibrating substrate. At lower vibration amplitudes (ξ{sub s} ∼ 10{sup −9} m), the improved heat transfer is mainly due to the detachment of vapor bubbles from the heated surface and the induced thermal mixing. Upon increasing the vibration amplitude (ξ{sub s} ∼ 10{sup −8} m), the heat transfer becomes more substantial due to the rapid bursting of vapor bubbles happening at the liquid-air interface as a consequence of capillary waves travelling in the thin liquid film between the vapor bubble and the air. Further increases then lead to rapid atomization that continues to enhance the heat transfer. An acoustic wave displacement amplitude on the order of 10{sup −8} m with 10{sup 6} Hz order frequencies is observed to produce an improvement of up to 50% reduction in the surface temperature over the case without acoustic excitation.

  17. Fluid induced structural vibrations in steam generators and heat exchangers

    Fluid-elastic instability (FEI) in tube bundle heat exchangers was studied experimentally. The motion of an array of 15 stainless steel vibrating tubes (Φ 25.4mm) in water cross-flow, suspended using stainless steel piano wire has been recorded with a CCD camera. The individual motion and relative motion of the tubes are reported and can be used for computational model validation. The relative displacement of the tubes allows identification of the most potentially damaging patterns of tube bundle vibration. A critical reduced velocity may be determined by specification of an allowable limit on tube motion amplitude. Measurements were made for various tube array configurations, tube natural frequencies and flow conditions. (author)

  18. Tyre induced vibrations of the car-trailer system

    Beregi, S.; Takács, D.; Stépán, G.

    2016-02-01

    The lateral and yaw dynamics of the car-trailer combination are analysed by means of a single track model. The equations of motion are derived rigorously by means of the Appell-Gibbs equations for constant longitudinal velocity of the vehicle. The tyres are described with the help of the so-called delayed tyre model, which is based on a brush model with pure rolling contact. The lateral forces and aligning torques of the tyre/road interaction are calculated via the instantaneous lateral deformations in the contact patches. The linear stability analysis of the rectilinear motion is performed via the analytically determined characteristic function of the system. Stability charts are constructed with respect to the vehicle longitudinal velocity and the payload position on the trailer. Self-excited lateral vibrations are detected with different vibration modes at low and at high longitudinal speeds of the vehicle. The effects of the tyre parameters are also investigated.

  19. Mitigation of Ice-Induced Vibrations for Offshore Platforms Using Tuned Mass Damper

    ZHANG Li; YUE Qian-jin; ZHANG Wen-shou

    2008-01-01

    The problems of ice-induced vibration have been noticed and concerned since the 1960s, but it has not been well resolved. One reason is that the dynamic interaction between ice and structure is so complicated that practical ice force model has not been developed. The recent full-scale tests conducted on jacket platforms in the Bohai Sea presented that ice could cause intense vibrations which endanger the facilities on the deck and make discomfort for the crew. In this paper, the strategy of mitigation of ice-induced offshore structure vibration is discussed. Based on field observations and understanding of the interaction between ice and structure, the absorption mitigation method to suppress ice-induced vibration is presented. The numerical simulations were conducted for a simplified model of platform attached with a Tuned Mass Damper (TMD) under ice force function and ice force time history. The simulation results show that TMD can favorably reduce ice-induced vibrations, therefore, it can be considered to be an alternative approach to utilize. Finally, the application possibilities of utilizing TMDs on other miniature offshore structures in ice-covered areas of marginal oil fields are discussed.

  20. Vortex-Induced Vibration Suppression of a Circular Cylinder with Vortex Generators

    Shi-bo Tao

    2016-01-01

    Full Text Available The vortex-induced vibration is one of the most important factors to make the engineering failure in wind engineering. This paper focuses on the suppression method of vortex-induced vibration that occurs on a circular cylinder fitted with vortex generators, based on the wind tunnel experiment. The effect of the vortex generators is presented with comparisons including the bare cylinder. The experimental results reveal that the vortex generators can efficiently suppress vortex-induced vibration of the circular cylinder. Vortex generator control can make the boundary layer profile fuller and hence more resistant to separation. The selections of skew angles and the angular position have a significant influence on the vortex generator control effect. By correlation analysis, it can be concluded that the vortex generators can inhibit the communication between the two shear layers and produce streamwise vortices to generate a disturbance in the spanwise direction.

  1. Vibration Mitigation without Dissipative Devices: First Large-Scale Testing of a State Switched Inducer

    Daniel Tirelli

    2014-01-01

    Full Text Available A new passive device for mitigating cable vibrations is proposed and its efficiency is assessed on 45-meter long taut cables through a series of free and forced vibration tests. It consists of a unilateral spring attached perpendicularly to the cable near the anchorage. Because of its ability to change the cable dynamic behaviour through intermittent activation, the device has been called state switched inducer (SSI. The cable behaviour is shown to be deeply modified by the SSI: the forced vibration response is anharmonicc and substantially reduced in amplitude whereas the free vibration decay is largely sped up through a beating phenomenon. The vibration mitigation effect is mainly due to the activation and coupling of various vibration modes, as evidenced in the response spectra of the equipped cable. This first large-scale experimental campaign shows that the SSI outperforms classical passive devices, thus paving the way to a new kind of low-cost vibration mitigation systems which do not rely on dissipation.

  2. MULTI-MODE OF VORTEX-INDUCED VIBRATION OF A FLEXIBLE CIRCULAR CYLINDER

    XIE Fang-fang; DENG Jian; ZHENG Yao

    2011-01-01

    The vortex-induced vibration of a flexible circular cylinder is investigated at a constant Reynolds number of 1 000.The finite-volume method on moving meshes is applied for the fluid flow,and the Euler-Bemoulli beam theory is used to model the dynamic response of a flexible cylinder.The relationship between the reduced velocity and the amplitude response agrees well with the experimental results.Moreover,five different vibrating modes appear in the simulation.From the comparisons of their vortex structures,the strength of the wake flow is related to the exciting vibrating mode and different vortex patterns arise for different vibrating modes.Only 2P pattern appears in the first vibrating mode while 2S-2P patterns occur in the other vibrating modes if monitoring at different sections along the length of the cylinder.The vibration of the flexible cylinder can also greatly alter the three-dimensionality in the wake,which needs further studies in our future work,especially in the transition region for the Reynolds number from 170 to 300.

  3. Shallow Water Acoustic Laboratory

    Federal Laboratory Consortium — FUNCTION: Supports experimental research where high-frequency acoustic scattering and surface vibration measurements of fluid-loaded and non-fluid-loaded structures...

  4. Tactile perception of skin and skin cream by friction induced vibrations.

    Ding, Shuyang; Bhushan, Bharat

    2016-11-01

    Skin cream smooths, softens, and moistens skin by altering surface roughness and tribological properties of skin. Sliding generates vibrations that activate mechanoreceptors located in skin. The brain interprets tactile information to identify skin feel. Understanding the tactile sensing mechanisms of skin with and without cream treatment is important to numerous applications including cosmetics, textiles, and robotics sensors. In this study, frequency spectra of friction force and friction induced vibration signals were carried out to investigate tactile perception by an artificial finger sliding on skin. The influence of normal load, velocity, and cream treatment time were studied. Coherence between friction force and vibration signals were found. The amplitude of vibration decreased after cream treatment, leading to smoother perception. Increasing normal load or velocity between contacting surfaces generated a smoother perception with cream treatment, but rougher perception without treatment. As cream treatment time increases, skin becomes smoother. The related mechanisms are discussed. PMID:27474814

  5. First international symposium on Flow Induced Noise and Vibration Issues and Aspects

    Rosa, Sergio; Franco, Francesco; Guyader, Jean-Louis; Hambric, Stephen; Flinovia - Flow Induced Noise and Vibration Issues and Aspects

    2015-01-01

    Flow induced vibration and noise (FIVN) remains a critical research topic. Even after over 50 years of intensive research, accurate and cost-effective FIVN simulation and measurement techniques remain elusive. This book gathers the latest research from some of the most prominent experts in the field. It describes methods for characterizing wall pressure fluctuations, including subsonic and supersonic turbulent boundary layer flows over smooth and rough surfaces using computational methods like Large Eddy Simulation;
for inferring wall pressure fluctuations using inverse techniques based on panel vibrations or holographic pressure sensor arrays;
for calculating the resulting structural vibrations and radiated sound using traditional finite element methods, as well as advanced methods like Energy Finite Elements;
for using scaling approaches to universally collapse flow-excited vibration and noise spectra; and for computing time histories of structural response, including alternating stresses. This book p...

  6. Scale-model characterization of flow-induced vibrational response of FFTF reactor internals

    Fast Test Reactor core internal and peripheral components were assessed for flow-induced vibrational characteristics under scaled and simulated prototype flow conditions in the Hydraulic Core Mockup as an integral part of the Fast Test Reactor Vibration Program. The Hydraulic Core Mockup was an 0.285 geometric scale model of the Fast Test Reactor internals designed to simulate prototype vibrational and hydraulic characteristics. Using water to simulate sodium coolant, vibrational characteristics were measured and determined for selected model components over the scaled flow range of 36 to 110%. Additionally, in-situ shaker tests were conducted on selected Hydraulic Core Mockup outlet plenum components to establish modal characteristics. Most components exhibited resonant response at all test flow rates; however, the measured dynamic response was neither abnormal nor anomalously flow-rate dependent, and the predicted prototype components' response were deemed acceptable

  7. Calculation of the ex-core neutron noise induced by fuel vibrations in PWRs

    Calculation of the neutron noise induced by fuel assembly vibrations in two pressurized water reactor (PWR) cores has been performed to investigate the effect of cycle burnup on the properties of the ex-core detector noise. Pendular vibrations of individual fuel assemblies were assumed to occur at different locations in the core. The auto power spectra density (APSD) of the ex-core detector noise was evaluated with the assumption of stochastic vibrations along a random two-dimensional trajectory. The results show that no general monotonic variation of APSD was found. The increase of APSD occurs predominantly for peripheral assemblies. Assuming simultaneous vibrations of a number of fuel assemblies uniformly distributed over the core with the more realistic perturbation model, the effect of the peripheral assemblies will dominate and the increase of the amplitude of the ex-core neutron noise with burnup can be confirmed. (author)

  8. Low dose ionizing radiation induced acoustic neuroma: A putative link?

    Sachin A Borkar

    2012-01-01

    Full Text Available Although exposure to high dose ionizing radiation (following therapeutic radiotherapy has been incriminated in the pathogenesis of many brain tumors, exposure to chronic low dose ionizing radiation has not yet been shown to be associated with tumorigenesis. The authors report a case of a 50-year-old atomic reactor scientist who received a cumulative dose of 78.9 mSv over a 10-year period and was detected to have an acoustic neuroma another 15 years later. Although there is no proof that exposure to ionizing radiation was the cause for the development of the acoustic neuroma, this case highlights the need for extended follow-up periods following exposure to low dose ionizing radiation.

  9. Flow-induced vibration analysis of heat exchanger and steam generator designs

    Tube and shell heat exchange components such as steam generators, heat exchangers and condensers are essential parts of CANDU nuclear power stations. Excessive flow-induced vibration may cause tube failures by fatigue or more likely by fretting-wear. Such failures may lead to station shutdowns that are very undesirable in terms of lost production. Hence good performance and reliability dictate a thorough flow-induced vibration analysis at the design stage. This paper presents our approach and techniques in this respect. (author)

  10. Fluidic harvesters in free stream turbulence undergoing flow-induced vibrations or flutter

    Gomez, Joan; Azadeh Ranjbar, Vahid; Goushcha, Oleg; Andreopoulos, Yiannis; Elvin, Niell

    2015-11-01

    In the present experimental work we investigated the performance of fluidic harvesters consisting of cylindrical body mounted of the tip of a flexible beam in the presence of nearly homogeneous and isotropic turbulence. Circular, semi-circular and square shapes have been tested. It was found that turbulence interferes with resonance conditions between the flow and the structure in the case of vortex induced vibrations and has absolutely no effect in flutter dominated case. As a result, turbulence increases the power output of non-linear harvesters subjected to vortex induces vibration and it has no effect in harvester under flutter conditions. Supported by NSF Grant: CBET #1033117.