WorldWideScience

Sample records for acoustically induced vibration

  1. Acoustically Induced Vibration of Structures: Reverberant Vs. Direct Acoustic Testing

    Science.gov (United States)

    Kolaini, Ali R.; O'Connell, Michael R.; Tsoi, Wan B.

    2009-01-01

    Large reverberant chambers have been used for several decades in the aerospace industry to test larger structures such as solar arrays and reflectors to qualify and to detect faults in the design and fabrication of spacecraft and satellites. In the past decade some companies have begun using direct near field acoustic testing, employing speakers, for qualifying larger structures. A limited test data set obtained from recent acoustic tests of the same hardware exposed to both direct and reverberant acoustic field testing has indicated some differences in the resulting structural responses. In reverberant acoustic testing, higher vibration responses were observed at lower frequencies when compared with the direct acoustic testing. In the case of direct near field acoustic testing higher vibration responses appeared to occur at higher frequencies as well. In reverberant chamber testing and direct acoustic testing, standing acoustic modes of the reverberant chamber or the speakers and spacecraft parallel surfaces can strongly couple with the fundamental structural modes of the test hardware. In this paper data from recent acoustic testing of flight hardware, that yielded evidence of acoustic standing wave coupling with structural responses, are discussed in some detail. Convincing evidence of the acoustic standing wave/structural coupling phenomenon will be discussed, citing observations from acoustic testing of a simple aluminum plate. The implications of such acoustic coupling to testing of sensitive flight hardware will be discussed. The results discussed in this paper reveal issues with over or under testing of flight hardware that could pose unanticipated structural and flight qualification issues. Therefore, it is of paramount importance to understand the structural modal coupling with standing acoustic waves that has been observed in both methods of acoustic testing. This study will assist the community to choose an appropriate testing method and test setup in

  2. Droplet Manipulation Using Acoustic Streaming Induced by a Vibrating Membrane.

    Science.gov (United States)

    Phan, Hoang Van; Alan, Tuncay; Neild, Adrian

    2016-06-01

    We present a simple method for on-demand manipulation of aqueous droplets in oil. With numerical simulations and experiments, we show that a vibrating membrane can produce acoustic streaming. By making use of this vortical flow, we manage to repulse the droplets away from the membrane edges. Then, by simply aligning the membrane at 45° to the flow, the droplets can be forced to follow the membrane's boundaries, thus steering them across streamlines and even between different oil types. We also characterize the repulsion and steering effect with various excitation voltages at different water and oil flow rates. The maximum steering frequency we have achieved is 165 Hz. The system is extremely robust and reliable: the same membrane can be reused after many days and with different oils and/or surfactants at the same operating frequency.

  3. 3D Characteristic Diagram of Acoustically Induced Surface Vibration with Different Landmines Buried

    Institute of Scientific and Technical Information of China (English)

    吴智强; 张燕丽; 王驰; 朱俊; 徐文文; 袁志文

    2016-01-01

    The 3Dcharacteristic diagram of acoustically induced surface vibration was employed to study the influence of different buried landmines on the acoustic detection signal. By using the vehicular experimental system for acoustic landmine detection and the method of scanning detection, the 3D characteristic diagrams of surface vibration were measured when different objects were buried underground, including big plastic landmine, small plastic landmine, big metal landmine and bricks. The results show that, under the given conditions, the surface vi-bration amplitudes of big plastic landmine, big metal landmine, small plastic landmine and bricks decrease in turn. The 3D characteristic diagrams of surface vibration can be used to further identify the locations of buried land-mines.

  4. Acoustic streaming induced by ultrasonic flexural vibrations and associated enhancement of convective heat transfer.

    Science.gov (United States)

    Loh, Byoung-Gook; Hyun, Sinjae; Ro, Paul I; Kleinstreuer, Clement

    2002-02-01

    Acoustic streaming induced by ultrasonic flexural vibrations and the associated convection enhancement are investigated. Acoustic streaming pattern, streaming velocity, and associated heat transfer characteristics are experimentally observed. Moreover, analytical analysis based on Nyborg's formulation is performed along with computational fluid dynamics (CFD) simulation using a numerical solver CFX 4.3. Two distinctive acoustic streaming patterns in half-wavelength of the flexural vibrations are observed, which agree well with the theory. However, acoustic streaming velocities obtained from CFD simulation, based on the incompressible flow assumption, exceed the theoretically estimated velocity by a factor ranging from 10 to 100, depending upon the location along the beam. Both CFD simulation and analytical analysis reveal that the acoustic streaming velocity is proportional to the square of the vibration amplitude and the wavelength of the vibrating beam that decreases with the excitation frequency. It is observed that the streaming velocity decreases with the excitation frequency. Also, with an open-ended channel, a substantial increase in streaming velocity is observed from CFD simulations. Using acoustic streaming, a temperature drop of 40 degrees C with a vibration amplitude of 25 microm at 28.4 kHz is experimentally achieved.

  5. Signal analysis of acoustic and flow-induced vibrations of BWR main steam line

    Energy Technology Data Exchange (ETDEWEB)

    Espinosa-Paredes, G., E-mail: gepe@xanum.uam.mx [División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana-Iztapalapa, México, D.F. 09340 (Mexico); Prieto-Guerrero, A. [División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana-Iztapalapa, México, D.F. 09340 (Mexico); Núñez-Carrera, A. [Comisión Nacional de Seguridad Nuclear y Salvaguardias, Doctor Barragán 779, Col. Narvarte, México, D.F. 03020 (Mexico); Vázquez-Rodríguez, A. [División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana-Iztapalapa, México, D.F. 09340 (Mexico); Centeno-Pérez, J. [Instituto Politécnico Nacional, Escuela Superior de Física y Matemáticas Unidad Profesional “Adolfo López Mateos”, Av. IPN, s/n, México, D.F. 07738 (Mexico); Espinosa-Martínez, E.-G. [Departamento de Sistemas Energéticos, Universidad Nacional Autónoma de México, México, D.F. 04510 (Mexico); and others

    2016-05-15

    Highlights: • Acoustic and flow-induced vibrations of BWR are analyzed. • BWR performance after extended power uprate is considered. • Effect of acoustic side branches (ASB) is analyzed. • The ASB represents a reduction in the acoustic loads to the steam dryer. • Methodology developed for simultaneous analyzing the signals in the MSL. - Abstract: The aim of this work is the signal analysis of acoustic waves due to phenomenon known as singing in Safety Relief Valves (SRV) of the main steam lines (MSL) in a typical BWR5. The acoustic resonance in SRV standpipes and fluctuating pressure is propagated from SRV to the dryer through the MSL. The signals are analyzed with a novel method based on the Multivariate Empirical Mode Decomposition (M-EMD). The M-EMD algorithm has the potential to find common oscillatory modes (IMF) within multivariate data. Based on this fact, we implement the M-EMD technique to find the oscillatory mode in BWR considering the measurements obtained collected by the strain gauges located around the MSL. These IMF, analyzed simultaneously in time, allow obtaining an estimation of the effects of the multiple-SRV in the MSL. Two scenarios are analyzed: the first is the signal obtained before the installation of the acoustic dampers (ASB), and the second, the signal obtained after installation. The results show the effectiveness of the ASB to damp the strong resonances when the steam flow increases, which represents an important reduction in the acoustic loads to the steam dryer.

  6. International Conference on Acoustics and Vibration

    CERN Document Server

    Chaari, Fakher; Walha, Lasaad; Abdennadher, Moez; Abbes, Mohamed; Haddar, Mohamed

    2017-01-01

    The book provides readers with a snapshot of recent research and industrial trends in field of industrial acoustics and vibration. Each chapter, accepted after a rigorous peer-review process, reports on a selected, original piece of work presented and discussed at International Conference on Acoustics and Vibration (ICAV2016), which was organized by the Tunisian Association of Industrial Acoustics and Vibration (ATAVI) and held March 21-23, in Hammamet, Tunisia. The contributions, mainly written by north African authors, covers advances in both theory and practice in a variety of subfields, such as: smart materials and structures; fluid-structure interaction; structural acoustics as well as computational vibro-acoustics and numerical methods. Further topics include: engines control, noise identification, robust design, flow-induced vibration and many others.This book provides a valuable resource for both academics and professionals dealing with diverse issues in applied mechanics. By combining advanced theori...

  7. Nonlinear vibration and radiation from a panel with transition to chaos induced by acoustic waves

    Science.gov (United States)

    Maestrello, Lucio; Frendi, Abdelkader; Brown, Donald E.

    1992-01-01

    The dynamic response of an aircraft panel forced at resonance and off-resonance by plane acoustic waves at normal incidence is investigated experimentally and numerically. Linear, nonlinear (period doubling) and chaotic responses are obtained by increasing the sound pressure level of the excitation. The response time history is sensitive to the input level and to the frequency of excitation. The change in response behavior is due to a change in input conditions, triggered either naturally or by modulation of the bandwidth of the incident waves. Off-resonance, bifurcation is diffused and difficult to maintain, thus the panel response drifts into a linear behavior. The acoustic pressure emanated by the panel is either linear or nonlinear as is the vibration response. The nonlinear effects accumulate during the propagation with distance. Results are also obtained on the control of the panel response using damping tape on aluminum panel and using a graphite epoxy panel having the same size and weight. Good agreement is obtained between the experimental and numerical results.

  8. Coupling between plate vibration and acoustic radiation

    Science.gov (United States)

    Frendi, Abdelkader; Maestrello, Lucio; Bayliss, Alvin

    1993-01-01

    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.

  9. Acoustic and vibration environments for laboratory experiments in space

    Science.gov (United States)

    Rader, W. P.

    1981-01-01

    The basic parameters of random noise and vibration are described, and typical environments for the launch phase and orbital operations are presented. For the latter, both acoustically induced and structure-borne, thruster-included vibration are addressed, using data obtained during the Skylab and Titan programs.

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

    Energy Technology Data Exchange (ETDEWEB)

    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

  11. 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

    Institute of Scientific and Technical Information of China (English)

    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.

  12. Acoustic and Vibration Environment for Crew Launch Vehicle Mobile Launcher

    Science.gov (United States)

    Vu, Bruce T.

    2007-01-01

    A launch-induced acoustic environment represents a dynamic load on the exposed facilities and ground support equipment (GSE) in the form of random pressures fluctuating around the ambient atmospheric pressure. In response to these fluctuating pressures, structural vibrations are generated and transmitted throughout the structure and to the equipment items supported by the structure. Certain equipment items are also excited by the direct acoustic input as well as by the vibration transmitted through the supporting structure. This paper presents the predicted acoustic and vibration environments induced by the launch of the Crew Launch Vehicle (CLV) from Launch Complex (LC) 39. The predicted acoustic environment depicted in this paper was calculated by scaling the statistically processed measured data available from Saturn V launches to the anticipated environment of the CLV launch. The scaling was accomplished by using the 5-segment Solid Rocket Booster (SRB) engine parameters. Derivation of vibration environment for various Mobile Launcher (ML) structures throughout the base and tower was accomplished by scaling the Saturn V vibration environment.

  13. Force Measurements in Vibration and Acoustic Tests

    Science.gov (United States)

    Scharton, T. D.

    1996-01-01

    The advent of triaxial, piezoelectric force gages and the associated signal processing is a precursor to several dynamics testing innovations. This new technology is applicable to spacecraft programs that JPL manages. An application of force measurement is force limiting (when testing spacecraft in random vibration tests). Base-drive and acoustic modal testing is a potential application.

  14. Surface acoustic wave (SAW) vibration sensors.

    Science.gov (United States)

    Filipiak, Jerzy; Solarz, Lech; Steczko, Grzegorz

    2011-01-01

    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.

  15. Surface Acoustic Wave (SAW Vibration Sensors

    Directory of Open Access Journals (Sweden)

    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.

  16. Vibration and acoustic testing of spacecraft

    Science.gov (United States)

    Scharton, T. D.

    2002-01-01

    Spacecraft are subjected to a variety of dynamics environments, which may include: quasi-static, vibration and acoustic loads at launch: pyrotechnic shocks generated by separation mechanisms; on orbit jitter; and sometimes, planetary landing loads. There is a trend in the aerospace industry to rely more on structural analyses and less on testing to simulate these environments, because dynamics testing of spacecraft is time consuming, risky and expensive.

  17. Vibration and acoustic environments for payload/cargo integration

    Science.gov (United States)

    Hill, R. E.; Coody, M. C.

    1983-01-01

    Shuttle orbiter launch vibration and acoustic environments for cargo bay/payload interfaces are predicted. Data acquired during Shuttle flight tests are compared with the preflight estimates. Vibration response data for payload attachment locations are presented, along with acoustic data in the form of noise-level spectra measured at various locations in the cargo bay and space averages of the noise levels. It is shown that the payload-bay vibration and acoustic environments are generally less severe than predicted.

  18. Damping of acoustic vibrations in gold nanoparticles

    Science.gov (United States)

    Pelton, Matthew; Sader, John E.; Burgin, Julien; Liu, Mingzhao; Guyot-Sionnest, Philippe; Gosztola, David

    2009-08-01

    Studies of acoustic vibrations in nanometre-scale particles can provide fundamental insights into the mechanical properties of materials because it is possible to precisely characterize and control the crystallinity and geometry of such nanostructures. Metal nanoparticles are of particular interest because they allow the use of ultrafast laser pulses to generate and probe high-frequency acoustic vibrations, which have the potential to be used in a variety of sensing applications. So far, the decay of these vibrations has been dominated by dephasing due to variations in nanoparticle size. Such inhomogeneities can be eliminated by performing measurements on single nanoparticles deposited on a substrate, but unknown interactions between the nanoparticles and the substrate make it difficult to interpret the results of such experiments. Here, we show that the effects of inhomogeneous damping can be reduced by using bipyramidal gold nanoparticles with highly uniform sizes. The inferred homogeneous damping is due to the combination of damping intrinsic to the nanoparticles and the surrounding solvent; the latter is quantitatively described by a parameter-free model.

  19. Coherent acoustic vibration of metal nanoshells.

    Science.gov (United States)

    Guillon, C; Langot, P; Del Fatti, N; Vallée, F; Kirakosyan, A S; Shahbazyan, T V; Cardinal, T; Treguer, M

    2007-01-01

    Using time-resolved pump-probe spectroscopy, we have performed the first investigation of the vibrational modes of gold nanoshells. The fundamental isotropic mode launched by a femtosecond pump pulse manifests itself in a pronounced time-domain modulation of the differential transmission probed at the frequency of nanoshell surface plasmon resonance. The modulation amplitude is significantly stronger, and the period is longer than that in a gold nanoparticle of the same overall size, in agreement with theoretical calculations. This distinct acoustical signature of nanoshells provides a new and efficient method for identifying these versatile nanostructures and for studying their mechanical and structural properties.

  20. Sensitive acoustic vibration sensor using single-mode fiber tapers.

    Science.gov (United States)

    Li, Yi; Wang, Xiaozhen; Bao, Xiaoyi

    2011-05-01

    Optical fiber sensors are a good alternative to piezoelectric devices in electromagnetic sensitive environments. In this study, we reported a fiber acoustic sensor based on single-mode fiber (SMF) tapers. The fiber taper is used as the sensing arm in a Mach-Zehnder interferometer. Benefiting from their micrometer dimensions, fiber tapers have shown higher sensitivities to the acoustic vibrations than SMFs. Under the same conditions, the thinnest fiber taper in this report, with a diameter of 1.7 µm, shows a 20 dB improvement in the signal to noise ratio as compared to that of an SMF. This acoustic vibration sensor can detect the acoustic waves over the frequencies of 30 Hz-40 kHz, which is limited by the acoustic wave generator in experiments. We also discussed the phase changes of fiber tapers with different diameters under acoustic vibrations.

  1. Materials for Damping Ambient Acoustic and Vibration Signals Project

    Data.gov (United States)

    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...

  2. Man-Induced Vibrations

    DEFF Research Database (Denmark)

    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...... concerned with spectator-induced vertical vibrations on grandstands. The idea is to use impulse response analysis and base the load description on the load impulse. If the method is feasable, it could be used in connection with the formulation of requirements in building codes. During the last two decades...

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

    Institute of Scientific and Technical Information of China (English)

    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.

  4. Acoustic buffeting by infrasound in a low vibration facility

    Science.gov (United States)

    MacLeod, B. P.; Hoffman, J. E.; Burke, S. A.; Bonn, D. A.

    2016-09-01

    Measurement instruments and fabrication tools with spatial resolution on the atomic scale require facilities that mitigate the impact of vibration sources in the environment. One approach to protection from vibration in a building's foundation is to place the instrument on a massive inertia block, supported on pneumatic isolators. This opens the questions of whether or not a massive floating block is susceptible to acoustic forces, and how to mitigate the effects of any such acoustic buffeting. Here this is investigated with quantitative measurements of vibrations and sound pressure, together with finite element modeling. It is shown that a particular concern, even in a facility with multiple acoustic enclosures, is the excitation of the lowest fundamental acoustic modes of the room by infrasound in the low tens of Hz range, and the efficient coupling of the fundamental room modes to a large inertia block centered in the room.

  5. Acoustic buffeting by infrasound in a low vibration facility.

    Science.gov (United States)

    MacLeod, B P; Hoffman, J E; Burke, S A; Bonn, D A

    2016-09-01

    Measurement instruments and fabrication tools with spatial resolution on the atomic scale require facilities that mitigate the impact of vibration sources in the environment. One approach to protection from vibration in a building's foundation is to place the instrument on a massive inertia block, supported on pneumatic isolators. This opens the questions of whether or not a massive floating block is susceptible to acoustic forces, and how to mitigate the effects of any such acoustic buffeting. Here this is investigated with quantitative measurements of vibrations and sound pressure, together with finite element modeling. It is shown that a particular concern, even in a facility with multiple acoustic enclosures, is the excitation of the lowest fundamental acoustic modes of the room by infrasound in the low tens of Hz range, and the efficient coupling of the fundamental room modes to a large inertia block centered in the room.

  6. A comparison of acoustic and random vibration testing of spacecraft

    Science.gov (United States)

    Bangs, W. F.

    1974-01-01

    Before selecting the most suitable testing technique in a particular case, it has to be considered which of the two methods duplicates better the distribution of vibration responses to be expected during the actual launch phase. An investigation is conducted of the case of a large, low density spacecraft launched by a vehicle which produces significant acoustic noise and transmits relatively little vibration through the mechanical path provided by the vehicle structure in the area of the spacecraft interface. Criteria for vibration-acoustic equivalence are discussed along with tests conducted with the Synchronous Meteorological Satellite, the Radio Astronomy Explorer, and the Orbiting Geophysical Spacecraft. The investigation indicates that the vibration test is generally a poor substitute for an acoustic study.-

  7. Multi-objective optimization of acoustic black hole vibration absorbers.

    Science.gov (United States)

    Shepherd, Micah R; Feurtado, Philip A; Conlon, Stephen C

    2016-09-01

    Structures with power law tapers exhibit the acoustic black hole (ABH) effect and can be used for vibration reduction. However, the design of ABHs for vibration reduction requires consideration of the underlying theory and its regions of validity. To address the competing nature of the best ABH design for vibration reduction and the underlying theoretical assumptions, a multi-objective approach is used to find the lowest frequency where both criteria are sufficiently met. The Pareto optimality curve is estimated for a range of ABH design parameters. The optimal set could then be used to implement an ABH vibration absorber.

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

    Institute of Scientific and Technical Information of China (English)

    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.

  9. Band Width of Acoustic Resonance Frequency Relatively Natural Frequency of Fuel Rod Vibration

    Energy Technology Data Exchange (ETDEWEB)

    Proskuryakov, Konstantin Nicolaevich; Moukhine, V.S.; Novikov, K.S.; Galivets, E.Yu. [MPEI - TU, 14, Krasnokazarmennaya str., Moscow, 111250 (Russian Federation)

    2009-06-15

    In flow induced vibrations the fluid flow is the energy source that causes vibration. Acoustic resonance in piping may lead to severe problems due to over-stressing of components or significant losses of efficiency. Steady oscillatory flow in NPP primary loop can be induced by the pulsating flow introduced by reactor circulating pump or may be set up by self-excitation. Dynamic forces generated by the turbulent flow of coolant in reactor cores cause fuel rods (FR) and fuel assembly (FA) to vibrate. Flow-induced FR and FA vibrations can generally be broken into three groups: large amplitude 'resonance type' vibrations, which can cause immediate rod failure or severe damage to the rod and its support structure, middle amplitude 'within bandwidth of resonance frequency type' vibrations responsible for more gradual wear and fatigue at the contact surface between the fuel cladding and rod support and small amplitude vibrations, 'out of bandwidth of resonance frequency type' responsible for permissible wear and fatigue at the contact surface between the fuel cladding and rod support. Ultimately, these vibration types can result in a cladding breach, and therefore must be accounted for in the thermal hydraulic design of FR and FA and reactor internals. In paper the technique of definition of quality factor (Q) of acoustic contour of the coolant is presented. The value of Q defines a range of frequencies of acoustic fluctuations of the coolant within which the resonance of oscillations of the structure and the coolant is realized. Method of evaluation of so called band width (BW) of acoustic resonance frequency is worked out and presented in the paper. BW characterises the range of the frequency of coolant pressure oscillations within which the frequency of coolant pressure oscillations matches the fuel assembly's natural frequency of vibration (its resonance frequency). Paper show the way of detuning acoustic resonance from natural

  10. Vibration and acoustic testing of TOPEX/Poseidon satellite

    Science.gov (United States)

    Boatman, Dave; Scharton, Terry; Hershfeld, Donald; Larkin, Paul

    1992-01-01

    The satellite was subjected to a 1.5G swept sine vibration test and a 146 dB overall level acoustic test, in accordance with Ariane launch vehicle requirements, at the NASA Goddard Space Flight Center. Extensive pretest analysis of the sine test was conducted to plan the input notching and to justify vibration testing the satellite only in the longitudinal axis. A unique measurement system was utilized to determine the six components of interface force between the shaker and the satellite in the sine vibration test. The satellite was heavily instrumented in both the sine vibration and acoustic test in order to insure that the launch loads were enveloped with appropriate margin and that satellite responses did not exceed the compatibilities of the structure and equipment. The test specification, objectives, instrumentation, and test results are described herein.

  11. Understanding acoustics an experimentalist’s view of acoustics and vibration

    CERN Document Server

    Garrett, Steven L

    2017-01-01

    This textbook provides a unified approach to acoustics and vibration suitable for use in advanced undergraduate and first-year graduate courses on vibration and fluids. The book includes thorough treatment of vibration of harmonic oscillators, coupled oscillators, isotropic elasticity, and waves in solids including the use of resonance techniques for determination of elastic moduli. Drawing on 35 years of experience teaching introductory graduate acoustics at the Naval Postgraduate School and Penn State, the author presents a hydrodynamic approach to the acoustics of sound in fluids that provides a uniform methodology for analysis of lumped-element systems and wave propagation that can incorporate attenuation mechanisms and complex media. This view provides a consistent and reliable approach that can be extended with confidence to more complex fluids and future applications. Understanding Acoustics opens with a mathematical introduction that includes graphing and statistical uncertainty, followed by five chap...

  12. A 24 channel acoustic/vibration test power amplifier

    Science.gov (United States)

    Barlett, F. R.

    1978-01-01

    In the present paper, the advantages and drawbacks of a multichannel amplifier operating in a vibration or acoustic facility are discussed. The configuration of the facility and the multichannel amplifier proposed is a compromise based on the particular requirements and anticipated work load in a specific case under consideration.

  13. Vibration Induced Microfluidic Atomization

    Science.gov (United States)

    Yeo, Leslie; Qi, Aisha; Friend, James

    2008-11-01

    We demonstrate rapid generation of micron aerosol droplets in a microfluidic device in which a fluid drop is exposed to surface vibration as it sits atop a piezoelectric substrate. Little, however, is understood about the processes by which these droplets form due to the complex hydrodynamic processes that occur across widely varying length and time scales. Through experiments, scaling theory and numerical modelling, we elucidate the interfacial destabilization mechanisms that lead to droplet formation. Droplets form due to the axisymmetric break-up of cylindrical liquid jets ejected as a consequence of interfacial destabilization. Their 10 μm size correlates with the jet radius and the instability wavelength, both determined from a viscous-capillary dominant force balance and confirmed through a numerical solution. With the exception of drops that spread into thin films with thicknesses on the order of the boundary layer dimension, the free surface is always observed to vibrate at the capillary-viscous resonance frequency despite the surface vibration frequency being several orders larger. This is contrary to common assumptions used in deriving subharmonic models resulting in a Mathieu equation, which has commonly led to spurious predictions in the droplet size.

  14. Chaotic vortex induced vibrations

    Energy Technology Data Exchange (ETDEWEB)

    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.

  15. Acoustically-Induced Electrical Signals

    Science.gov (United States)

    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.

  16. Active vibration and noise control by hybrid active acoustic panels

    Energy Technology Data Exchange (ETDEWEB)

    Stoebener, U.; Gaul, L. [Stuttgart Univ. (Germany). Inst. A fuer Mechanik

    2001-07-01

    In the present paper a hybrid passive and active treatment for vibration and noise reduction of plate type structures is proposed. The treatment is manufactured as sandwich structure and is called hybrid active acoustic panel. The passive component is used to reduce the vibration and sound radiation for high frequencies whereas the active part of the system is designed for the low frequency range. By selecting the thickness of the passive damping layer a certain frequency limit is defined, which divides the high and low frequency range. The actuator and sensor layout of the active component is evaluated by using the mode shapes of the low frequency range. According to the evaluated layout a hybrid active acoustic panel is manufactured and experimentally tested. The experimental results validate the proposed concept. (orig.)

  17. Vibration and Acoustic Testing for Mars Micromission Spacecraft

    Science.gov (United States)

    Kern, Dennis L.; Scharton, Terry D.

    1999-01-01

    The objective of the Mars Micromission program being managed by the Jet Propulsion Laboratory (JPL) for NASA is to develop a common spacecraft that can carry telecommunications equipment and a variety of science payloads for exploration of Mars. The spacecraft will be capable of carrying robot landers and rovers, cameras, probes, balloons, gliders or aircraft, and telecommunications equipment to Mars at much lower cost than recent NASA Mars missions. The lightweight spacecraft (about 220 Kg mass) will be launched in a cooperative venture with CNES as a TWIN auxiliary payload on the Ariane 5 launch vehicle. Two or more Mars Micromission launches are planned for each Mars launch opportunity, which occur every 26 months. The Mars launch window for the first mission is November 1, 2002 through April 2003, which is planned to be a Mars airplane technology demonstration mission to coincide with the 100 year anniversary of the Kittyhawk flight. Several subsequent launches will create a telecommunications network orbiting Mars, which will provide for continuous communication with lenders and rovers on the Martian surface. Dedicated science payload flights to Mars are slated to start in 2005. This new cheaper and faster approach to Mars exploration calls for innovative approaches to the qualification of the Mars Micromission spacecraft for the Ariane 5 launch vibration and acoustic environments. JPL has in recent years implemented new approaches to spacecraft testing that may be effectively applied to the Mars Micromission. These include 1) force limited vibration testing, 2) combined loads, vibration and modal testing, and 3) direct acoustic testing. JPL has performed nearly 200 force limited vibration tests in the past 9 years; several of the tests were on spacecraft and large instruments, including the Cassini and Deep Space One spacecraft. Force limiting, which measures and limits the spacecraft base reaction force using triaxial force gages sandwiched between the

  18. Vibration and acoustic response of an orthotropic composite laminated plate in a hygroscopic environment.

    Science.gov (United States)

    Zhao, Xin; Geng, Qian; Li, Yueming

    2013-03-01

    This paper is a study of the vibration and acoustic response characteristics of orthotropic laminated composite plate with simple supported boundary conditions excited by a harmonic concentrated force in a hygroscopic environment. First the natural vibration of the plate with the in-plane forces induced by hygroscopic stress is obtained analytically. Secondly, the sound pressure distribution of the plate at the far field is obtained using the Rayleigh integral. Furthermore, the sound radiation efficiency is deduced. Third, different ratios of elastic modulus in material principal directions are set to research the effects of increasing stiffness of the orthotropic plate on the vibration and acoustic radiation characteristics. Finally, to verify the theoretical solution, numerical simulations are also carried out with commercial finite software. It is found that the natural frequencies decrease with the increase of the moisture content and the first two order modes interconvert at high moisture content. The dynamic response and sound pressure level float to lower frequencies with elevated moisture content. Acoustic radiation efficiency generally floats to the low frequencies and decreases with an increase of moisture content. The dynamic and acoustic responses reduce and the coincidence frequency decreases with the enhanced stiffness.

  19. Surface Acoustic Wave Vibration Sensors for Measuring Aircraft Flutter

    Science.gov (United States)

    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.

  20. Prediction and Measurement of the Vibration and Acoustic Radiation of Panels Subjected to Acoustic Loading

    Science.gov (United States)

    Turner, Travis L.; Rizzi, Stephen A.

    1995-01-01

    Interior noise and sonic fatigue are important issues in the development and design of advanced subsonic and supersonic aircraft. Conventional aircraft typically employ passive treatments, such as constrained layer damping and acoustic absorption materials, to reduce the structural response and resulting acoustic levels in the aircraft interior. These techniques require significant addition of mass and only attenuate relatively high frequency noise transmitted through the fuselage. Although structural acoustic coupling is in general very important in the study of aircraft fuselage interior noise, analysis of noise transmission through a panel supported in an infinite rigid baffle (separating two semi-infinite acoustic domains) can be useful in evaluating the effects of active/adaptive materials, complex loading, etc. Recent work has been aimed at developing adaptive and/or active methods of controlling the structural acoustic response of panels to reduce the transmitted noise1. A finite element formulation was recently developed to study the dynamic response of shape memory alloy (SMA) hybrid composite panels (conventional composite panel with embedded SMA fibers) subject to combined acoustic and thermal loads2. Further analysis has been performed to predict the far-field acoustic radiation using the finite element dynamic panel response prediction3. The purpose of the present work is to validate the panel vibration and acoustic radiation prediction methods with baseline experimental results obtained from an isotropic panel, without the effect of SMA.

  1. The current status of measurement standards for acoustics and vibration at Inmetro

    OpenAIRE

    Ripper, Gustavo Palmeira; Hoffmann, Walter Erico

    2002-01-01

    ABSTRACT: The Division of Acoustics and Vibration (DIAVI) of INMETRO establishes, validates and maintains the Brazilian national measurement standards used for the realization of the units of physical quantities related to the field of acoustics and vibration. The basic vibration quantity realized by DIAVI is translational acceleration, from which the other motion quantities, i.e., velocity and displacement can be derived. Acoustical physical quantities include sound pressure and sound power...

  2. Analysis of Vibration and Acoustic Noise in Permanent Magnet Motors.

    Science.gov (United States)

    Hwang, Sangmoon

    The drive motor is a frequent source of vibration and acoustic noise in many precision spindle motors. One of the electromagnetic sources of vibration in permanent magnet motors is the torque ripple, consisting of the reluctance torque and electromagnetic torque fluctuation. This type of vibration is becoming more serious with the advent of new high-grade magnets with increased flux density. Acoustic noise of electromagnetic origin is difficult to predict and its exact mechanism is unclear. The mechanism of noise generation should be revealed to design a quieter motor which is the modern customer's demand. For motor operation at low speeds and loads, torque ripple due to the reluctance torque is often a source of vibration and control difficulty. The reluctance torque in a motor was calculated from the flux density by a finite element method and the Maxwell stress method. Effects of design parameters, such as stator slot width, permanent slot width, airgap length and magnetization direction, were investigated. Magnet pole shaping, by gradually decreasing the magnet thickness toward edges, yields a sinusoidal shape of the reluctance torque with reduced harmonics, thus reducing the vibration. This dissertation also presents two motor design techniques: stator tooth notching and rotor pole skewing with magnet pole shaping, and the effect of each method on the output torque. The analysis shows that the reluctance torque can be nearly eliminated by the suggested designs, with minimal sacrifice of the output torque. In permanent magnet DC motors, the most popular design type is the trapezoidal back electro-motive force (BEMF), for switched DC controllers. It is demonstrated that the output torque profile of one phase energized is qualitatively equivalent to the BEMF profile for motors with reduced reluctance torque. It implies that design of BEMF profile is possible by magnetic modeling of a motor, without expensive and time-consuming experiments for different designs

  3. Interferometric correlator for acoustic radiation and underlying structural vibration

    Science.gov (United States)

    Apostol, Adela; Kilpatrick, James; Markov, Vladimir; Bendiksen, Oddvar O.

    2016-12-01

    In this paper we discuss the background and principles of an optical non-contact sensor fusion concept, the Interferometric Correlator for Acoustic Radiation and Underlying Structural Vibration (ICARUSV) and give practical example of its capabilities, focusing on its ability to simultaneously capture, visualize and quantitatively characterize full-field non-stationary structural dynamics and unsteady radiated sound fields or transient flow fields around the structure of interest. The ICARUSV's multi-sensor design is based on a parallel architecture and therefore the data capture is fast and inherently support a wide variety of spatio-temporal or spatio-spectral analysis methods which characterize the structural or acoustic/flow field dynamics as it occurs in real time, including short-lived transient events. No other technology available today offers this level of multi-parameter multi-dimensional data1.

  4. Embedded Acoustic Black Holes for semi-passive broadband vibration attenuation in thin-walled structures

    Science.gov (United States)

    Zhao, Liuxian; Semperlotti, Fabio

    2017-02-01

    We explore the use of structure-embedded Acoustic Black Holes (ABH) to design thin-walled structural components exhibiting broadband vibration attenuation characteristics. The ABH is a geometric taper with a power-law profile fully integrated into the structural component and able to induce a smooth and progressive decrease of both the velocity and the wavelength of flexural waves. Previous studies have shown these characteristics to be critical to enable highly efficient vibration attenuation systems. The performance of ABH thin-walled structures is numerically and experimentally evaluated under both transient and steady state excitation conditions. Both numerical and experimental results suggest that the proposed approach enables highly efficient and broadband vibration attenuation performance.

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

    Directory of Open Access Journals (Sweden)

    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.

  6. Acoustic vibration sensor based on nonadiabatic tapered fibers.

    Science.gov (United States)

    Xu, Ben; Li, Yi; Sun, Miao; Zhang, Zhen-Wei; Dong, Xin-Yong; Zhang, Zai-Xuan; Jin, Shang-Zhong

    2012-11-15

    A simple and low-cost vibration sensor based on single-mode nonadiabatic fiber tapers is proposed and demonstrated. The environmental vibrations can be detected by demodulating the transmission loss of the nonadiabatic fiber taper. Theoretical simulations show that the transmission loss is related to the microbending of the fiber taper induced by vibrations. Unlike interferometric sensors, this vibration sensor does not need any feedback loop to control the quadrature point to obtain a stable performance. In addition, it has no requirement for the coherence of the light source and is insensitive to temperature changes. Experimental results show that this sensing system has a wide frequency response range from a few hertz to tens of kilohertz with the maximal signal to noise ratio up to 73 dB.

  7. Characteristics of Vibration Induced by Cavitation

    Institute of Scientific and Technical Information of China (English)

    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.

  8. Vibration damping using a spiral acoustic black hole.

    Science.gov (United States)

    Lee, Jae Yeon; Jeon, Wonju

    2017-03-01

    This study starts with a simple question: can the vibration of plates or beams be efficiently reduced using a lightweight structure that occupies a small space? As an efficient technique to damp vibration, the concept of an acoustic black hole (ABH) is adopted with a simple modification of the geometry. The original shape of an ABH is a straight wedge-type profile with power-law thickness, with the reduction of vibration in beams or plates increasing as the length of the ABH increases. However, in real-world applications, there exists an upper bound of the length of an ABH due to space limitations. Therefore, in this study, the authors propose a curvilinear shaped ABH using the simple mathematical geometry of an Archimedean spiral, which allows a uniform gap distance between adjacent baselines of the spiral. In numerical simulations, the damping performance increases as the arc length of the Archimedean spiral increases, regardless of the curvature of the spiral in the mid- and high-frequency ranges. Adding damping material to an ABH can also strongly enhance the damping performance while not significantly increasing the weight. In addition, the radiated sound power of a spiral ABH is similar to that of a standard ABH.

  9. Piezoelectric Shunt Vibration Damping of F-15 Panel under High Acoustic Excitation

    Science.gov (United States)

    Wu, Shu-Yau; Turner, Travis L.; Rizzi, Stephen A.

    2000-01-01

    At last year's SPIE symposium, we reported results of an experiment on structural vibration damping of an F-15 underbelly panel using piezoelectric shunting with five bonded PZT transducers. The panel vibration was induced with an acoustic speaker at an overall sound pressure level (OASPL) of about 90 dB. Amplitude reductions of 13.45 and 10.72 dB were achieved for the first and second modes, respectively, using single- and multiple-mode shunting. It is the purpose of this investigation to extend the passive piezoelectric shunt-damping technique to control structural vibration induced at higher acoustic excitation levels, and to examine the controllability and survivability of the bonded PZT transducers at these high levels. The shunting experiment was performed with the Thermal Acoustic Fatigue Apparatus (TAFA) at the NASA Langley Research Center using the same F-15 underbelly panel. The TAFA is a progressive wave tube facility. The panel was mounted in one wall of the TAFA test section using a specially designed mounting fixture such that the panel was subjected to grazing-incidence acoustic excitation. Five PZT transducers were used with two shunt circuits designed to control the first and second modes of the structure between 200 and 400 Hz. We first determined the values of the shunt inductance and resistance at an OASPL of 130 dB. These values were maintained while we gradually increased the OASPL from 130 to 154 dB in 6-dB steps. During each increment, the frequency response function between accelerometers on the panel and the acoustic excitation measured by microphones, before and after shunting, were recorded. Good response reduction was observed up to the 148dB level. The experiment was stopped at 154 dB due to wire breakage from vibration at a transducer wire joint. The PZT transducers, however, were still bonded well on the panel and survived at this high dB level. We also observed shifting of the frequency peaks toward lower frequency when the OASPL

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

    Institute of Scientific and Technical Information of China (English)

    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.

  11. Vibration-induced droplet atomization

    Science.gov (United States)

    Vukasinovic, Bojan

    The atomization of liquid drops is investigated experimentally using laser vibrometry, high-speed imaging, and particle tracking techniques. The spray is generated by a novel vibration-induced droplet atomization (VIDA) process in which a sessile drop is atomized by an underlying vibrating thin metal diaphragm, resulting in rapid ejection of small secondary droplets from the free surface of the primary drop. Under some conditions, the primary drop can be atomized extremely rapidly by a bursting-like mechanism (e.g., a 0.1 ml water drop can be atomized in 0.4 seconds). The present research has focused on four major areas: global characteristics of VIDA process, instability modes and free surface dynamics of the forced drop, mechanisms of the interface breakup, and parametric characterization of the ensuing spray. Prior to atomization, the drop free surface undergoes three transitions: from axisymmetric standing waves to azimuthal waves, to a newly-observed lattice mode, and to a disordered pre-ejection state. The droplet ejection results from localized collapse of surface troughs and initiation and ultimate breakup of momentary liquid spikes. Breakup begins with capillary pinch-off from spike tips and can be followed by additional pinching of liquid droplets. For a relatively low-viscosity liquid, e.g., water, a capillary-wave instability of the spike is observed in some cases, while for a very viscous liquid, e.g., a glycerin/water solution, the first breakup occurs near the stem of the spike, with or without subsequent breakup of the detached, elongated thread. Different mechanisms dominating the primary breakup of the spike are operative in the low- and high-viscosity ejection regimes. When ejection of the secondary droplets is triggered, the evolution and rate of atomization depend on the coupled dynamics of the primary drop and the vibrating diaphragm. Due to these dynamics, the process can be either self-intensifying or self-decaying. The resulting VIDA spray

  12. Wake Shield Facility Modal Survey Test in Vibration Acoustic Test Facility

    Science.gov (United States)

    1994-01-01

    Astronaut Ronald M. Sega stands beside the University of Houston's Wake Shield Facility before it undergoes a Modal Survey Test in the Vibration and Acoustic Test Facility Building 49, prior to being flown on space shuttle mission STS-60.

  13. Phase-sensitive imaging of tissue acoustic vibrations using spectrally encoded interferometry.

    Science.gov (United States)

    Ilgayev, Ovadia; Yelin, Dvir

    2013-08-26

    Acoustic vibrations in tissue are often difficult to image, requiring high-speed scanning, high sensitivity and nanometer-scale axial resolution. Here we use spectrally encoded interferometry to measure the vibration pattern of two-dimensional surfaces, including the skin of a volunteer, at nanometric resolution, without the need for rapid lateral scanning and with no prior knowledge of the driving acoustic waveform. Our results demonstrate the feasibility of this technique for measuring tissue biomechanics using simple and compact imaging probes.

  14. Light scattering from acoustic vibrational modes in confined structures

    Science.gov (United States)

    Bandhu, Rudra Shyam

    The acoustic vibrational modes and their light scattering intensities in confined structures such as supported films, double layer free-standing membrane and sub-micron sized wires on a free-standing membrane have been studied using Brillouin Light Scattering (BLS). Standing wave type acoustic phonons were recently observed in supported thin films of silicon oxy-nitride. We build upon this finding to study the acoustic modes in thin zinc selenide (ZnSe) films on gallium arsenide (GaAs). The surprising behaviour of the Brillouin intensities of the standing wave modes in ZnSe are explained in terms of interference of the elasto-optic scattering amplitudes from the film and substrate. Numerical calculations of the scattering cross-section, which takes into account ripple and elasto-optic scattering mechanism, agrees well with the experimental data. Light scattering studies of standing wave type modes in free-standing polymethyl methacrylate (PMMA) layer on Si3N4 were carried out. In these bilayer structures PMMA is much softer than Si3N 4, a property that leads to confinement of low frequency modes associated with the PMMA layer to within its boundaries. In addition, the flexural and the dilatational modes from the Si3N4 layer are observed and are found to hybridize with the standing wave modes from the PMMA layer. Our study of phonon modes in PMMA wires supported on a free-standing Si3N4 membrane extends our work on free-standing double layer membranes. In recent years there is much interest in the study of phonon modes in nano-scale structures such as wires or dots. Although much theoretical work has been carried out in this direction, no experiments exist that explore the dispersion of the phonon modes in such structures. Brillouin Light scattering is ideally suited for studying phonons in such reduced dimensions and our work represents the first effort in this direction. The spectra reveal modes which are quantized both along the width, as well along the thickness

  15. Vibration of a single microcapsule with a hard plastic shell in an acoustic standing wave field.

    Science.gov (United States)

    Koyama, Daisuke; Kotera, Hironori; Kitazawa, Natsuko; Yoshida, Kenji; Nakamura, Kentaro; Watanabe, Yoshiaki

    2011-04-01

    Observation techniques for measuring the small vibration of a single microcapsule of tens of nanometers in an acoustic standing wave field are discussed. First, simultaneous optical observation of a microbubble vibration by two methods is investigated, using a high-speed video camera, which permits two-dimensional observation of the bubble vibration, and a laser Doppler vibrometer (LDV), which can observe small bubble vibration amplitudes at high frequency. Bubbles of tens of micrometers size were trapped at the antinode of an acoustic standing wave generated in an observational cell. Bubble vibration at 27 kHz could be observed and the experimental results for the two methods showed good agreement. The radial vibration of microcapsules with a hard plastic shell was observed using the LDV and the measurement of the capsule vibration with radial oscillation amplitude of tens of nanometers was successful. The acoustic radiation force acting on microcapsules in the acoustic standing wave was measured from the trapped position of the standing wave and the radial oscillation amplitude of the capsules was estimated from the theoretical equation of the acoustic radiation force, giving results in good agreement with the LDV measurements. The radial oscillation amplitude of a capsule was found to be proportional to the amplitude of the driving sound pressure. A larger expansion ratio was observed for capsules closer to the resonance condition under the same driving sound pressure and frequency.

  16. Control of boundary layer transition location and plate vibration in the presence of an external acoustic field

    Science.gov (United States)

    Maestrello, L.; Grosveld, F. W.

    1991-01-01

    The experiment is aimed at controlling the boundary layer transition location and the plate vibration when excited by a flow and an upstream sound source. Sound has been found to affect the flow at the leading edge and the response of a flexible plate in a boundary layer. Because the sound induces early transition, the panel vibration is acoustically coupled to the turbulent boundary layer by the upstream radiation. Localized surface heating at the leading edge delays the transition location downstream of the flexible plate. The response of the plate excited by a turbulent boundary layer (without sound) shows that the plate is forced to vibrate at different frequencies and with different amplitudes as the flow velocity changes indicating that the plate is driven by the convective waves of the boundary layer. The acoustic disturbances induced by the upstream sound dominate the response of the plate when the boundary layer is either turbulent or laminar. Active vibration control was used to reduce the sound induced displacement amplitude of the plate.

  17. Vibration-induced liquefaction of granular suspensions.

    Science.gov (United States)

    Hanotin, C; Kiesgen de Richter, S; Marchal, P; Michot, L J; Baravian, C

    2012-05-11

    We investigate the mechanical behavior of granular suspensions subjected to coupled vibrations and shear. At high shear stress, whatever the mechanical vibration energy and bead size, the system behaves like a homogeneous suspension of hard spheres. At low shear stress, in addition to a dependence on bead size, vibration energy drastically influences the viscosity of the material that can decrease by more than 2 orders of magnitude. All experiments can be rationalized by introducing a hydrodynamical Peclet number defined as the ratio between the lubrication stress induced by vibrations and granular pressure. The behavior of vibrated wet and dry granular materials can then be unified by assimilating the hookean stress in dry media to the lubrication stress in suspensions.

  18. Towards identifying the dynamics of sliding by acoustic emission and vibration

    Science.gov (United States)

    Korchuganov, M. A.; Filippov, A. V.; Tarasov, S. Yu.; Podgornyh, O. A.; Shamarin, N. N.; Filippova, E. O.

    2016-11-01

    The results of experiments with high load and sliding speed sliding conditions on tribologically mated pairs such as steel 1045/steel 1045 (test 1), steel 1045/basalt (test 2) and Hadfield steel/basalt (test 3) have been carried out in order to identify their response in terms of the acoustic emission and vibration signals. The steel to rock and rock to steel transfer has been revealed by examining the worn surfaces of both steel and rock samples with the use of laser scanning microscopy. The AE signal characteristics have been determined for the tribological pairs studied. The dynamics of sliding has been evaluated by measuring the vibration accelerations. Relationship between wear mode and either acoustic emission signal or vibration signal has been established. The minimal vibration oscillations amplitude and acoustic emission signal energy have been found out in sliding Hadfield steel/basalt pair.

  19. Pulse-induced acoustoelectric vibrations in surface-gated GaAs-based quantum devices

    Science.gov (United States)

    Rahman, S.; Stace, T. M.; Langtangen, H. P.; Kataoka, M.; Barnes, C. H. W.

    2007-05-01

    We present the results of a numerical investigation which show the excitation of acoustoelectric modes of vibration in GaAs-based heterostructures due to sharp nanosecond electric-field pulses applied across surface gates. In particular, we show that the pulses applied in quantum information processing applications are capable of exciting acoustoelectric modes of vibration including surface acoustic modes which propagate for distances greater than conventional device dimensions. We show that the pulse-induced acoustoelectric vibrations are capable of inducing significant undesired perturbations to the evolution of quantum systems.

  20. Flow induced vibration studies on PFBR control plug components

    Energy Technology Data Exchange (ETDEWEB)

    Prakash, V., E-mail: prakash@igcar.gov.in [Fast Reactor Technology Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamilnadu (India); Kumar, P. Anup; Anandaraj, M.; Thirumalai, M.; Anandbabu, C.; Rajan, K.K. [Fast Reactor Technology Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamilnadu (India)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer Flow induced vibration studies on Prototype Fast Breeder Reactor control plug model carried out. Black-Right-Pointing-Pointer Velocity similitude was followed for the study. Black-Right-Pointing-Pointer Frequencies and amplitude of vibrations of various control plug components measured. Black-Right-Pointing-Pointer Overall values of vibration are well within permissible limits. - Abstract: The construction of Prototype Fast Breeder Reactor (PFBR), a 500 MWe liquid sodium cooled reactor, is in progress at Kalpakkam in India. Control plug (CP) is located right above the core subassemblies in the hot pool. Control plug is an important component as many of the critical reactor parameters are sensed and controlled by the components housed in the control plug assembly. In PFBR primary circuit, components are basically thin walled, slender shells with diameter to thickness ratio ranging from 100 to 650. These components are prone to flow induced vibrations. The existence of free liquid (sodium) surfaces, which is the source of sloshing phenomenon and the operation of primary sodium pump in the primary pool are other potential sources of vibration of reactor components. Control plug is a hollow cylindrical shell structure and provides passages and support for 12 absorber rod drive mechanisms (ARDM) which consists of 9 control and safety rods and 3 diverse safety rods, 210 thermo wells to measure the sodium temperature at the exit of various fuel subassemblies, three failed fuel localization modules (FFLM) and acoustic detectors. It consists of a core cover plate (CCP), which forms the bottom end, two intermediate supports plate, i.e. lower stay plate (LSP) and upper stay plate (USP) and an outer shell. The CCP is located at a distance of 1.3 m from the core top. With such a gap, there will be long free hanging length of the thermocouple sleeves, Delayed neutron detector (DND) sampling tubes and ARDM shroud tubes and hence they are

  1. Prediction of induced vibrations in stall

    Energy Technology Data Exchange (ETDEWEB)

    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)

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

    CERN Document Server

    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.

  3. Vibration and Acoustic Radiation from Orthogonally Stiffened Infinite Circular Cylindrical Shells in Water

    Institute of Scientific and Technical Information of China (English)

    陈军明; 黄玉盈; 曾革委

    2002-01-01

    Based on the motion differential equations of vibration and acoustic coupling system for thin elastic shells with ribs,by means of the Fourier integral transformation and the Fourier inverse transformation, as well as the stationary phasemethod, an analytic solution, which has satisfying computational effectiveness and precision, is derived for the solution tothe vibration and acoustic radiation from a submerged stiffened infinite circular cylinder with both ring and axial ribs. It iseasy to analyze the effect of stiffening supports in the acoustic radiation field by use of the formulas obtainod by the pre-sented method and corresponding numerical computation. It is shown that the axial-stiffeners can improve the mechanicaland acoustical characteristics. Moreover, the present method can be used to study the acoustic radiation mechanism of thetype of structure.

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

    Institute of Scientific and Technical Information of China (English)

    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.

  5. Characterization of vibration and acoustic noise in a gradient-coil insert.

    Science.gov (United States)

    Yao, G Z; Mechefske, C K; Rutt, B K

    2004-09-01

    High-speed switching of current in gradient coils within high magnetic field strength magnetic resonance imaging (MRI) scanners results in high acoustic sound pressure levels (SPL) in and around these machines. To characterize the vibration properties as well as the acoustic noise properties of the gradient coil, a finite-element (FE) model was developed using the dimensional design specifications of an available gradient-coil insert and the concentration of the copper windings in the coil. This FE model was then validated using experimentally collected vibration data. A computational acoustic noise model was then developed based on the validated FE model. The validation of the finite-element analysis results was done using experimental modal testing of the same gradient coil in a free-free state (no boundary constraints). Based on the validated FE model, boundary conditions (supports) were added to the model to simulate the operating condition when the gradient-coil insert is in place in an MRI machine. Vibration analysis results from the FE model were again validated through experimental vibration testing with the gradient-coil insert installed in the MRI scanner and excited using swept sinusoidal time waveforms. The simulation results from the computational acoustic noise model were also validated through experimental noise measurement from the gradient-coil insert in the MRI scanner using swept sinusoidal time waveform inputs. Comparisons show that the FE model predicts the vibration properties and the computational acoustic noise model predicts the noise characteristic properties extremely accurately.

  6. Seismic features of vibration induced by train

    Institute of Scientific and Technical Information of China (English)

    陈棋福; 李丽; 李纲; 陈凌; 彭文涛; 汤毅; 陈颙; 王夫运

    2004-01-01

    Based on schematically formulation of the vibrations induced by moving trains, this paper analyses the waveforms along the Datong-Qinhuangdao railroad in Northern China recorded in the suburban Huairou district of Beijing on March 8, 2003. It is illustrated that vibrations induced by train, except traditional recognized noises and interference effects, could be used as a seismic source to detect crustal structures with its advantage of abundant frequency spectrum, repeatability and no additional harm to the environment. It will bring lights to the traditional exploration seismology with the further studies of signal processing and interpretation methods, and related models and new observing systems.

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

    Institute of Scientific and Technical Information of China (English)

    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.

  8. Stochastic analysis of self-induced vibrations

    DEFF Research Database (Denmark)

    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...

  9. Acoustic vibration modes and electron-lattice coupling in self-assembled silver nanocolumns.

    Science.gov (United States)

    Burgin, J; Langot, P; Arbouet, A; Margueritat, J; Gonzalo, J; Afonso, C N; Vallée, F; Mlayah, A; Rossell, M D; Van Tendeloo, G

    2008-05-01

    Using ultrafast spectroscopy, we investigated electron-lattice coupling and acoustic vibrations in self-assembled silver nanocolumns embedded in an amorphous Al2O3 matrix. The measured electron-lattice energy exchange time is smaller in the nanocolumns than in bulk silver, with a value very close to that of isolated nanospheres with comparable surface to volume ratio. Two vibration modes were detected and ascribed to the breathing and extensional mode of the nanocolumns, in agreement with numerical simulations.

  10. A novel prediction method of vibration and acoustic radiation for rectangular plate with particle dampers

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Dongqiang; Wu, Chengjun [Xi' an Jiaotong University, Xi' an (China)

    2016-03-15

    Particle damping technology is widely used in mechanical and structural systems or civil engineering to reduce vibration and suppress noise as a result of its high efficiency, simplicity and easy implementation, low cost, and energy-saving characteristic without the need for any auxiliary power equipment. Research on particle damping theory has focused on the vibration response of the particle damping structure, but the acoustic radiation of the particle damping structure is rarely investigated. Therefore, a feasible modeling method to predict the vibration response and acoustic radiation of the particle damping structure is desirable to satisfy the actual requirements in industrial practice. In this paper, a novel simulation method based on multiphase flow theory of gas particle by COMSOL multiphysics is developed to study the vibration and acoustic radiation characteristics of a cantilever rectangular plate with Particle dampers (PDs). The frequency response functions and scattered far-field sound pressure level of the plate without and with PDs under forced vibration are predicted, and the predictions agree well with the experimental results. Results demonstrate that the added PDs have a significant effect on vibration damping and noise reduction for the primary structure. The presented work in this paper shows that the theoretical work is valid, which can provide important theoretical guidance for low-noise optimization design of particle damping structure. This model also has an important reference value for the noise control of this kind of structure.

  11. Vibration-induced drop atomization and bursting

    Science.gov (United States)

    James, A. J.; Vukasinovic, B.; Smith, Marc K.; Glezer, A.

    2003-02-01

    A liquid drop placed on a vibrating diaphragm will burst into a fine spray of smaller secondary droplets if it is driven at the proper frequency and amplitude. The process begins when capillary waves appear on the free surface of the drop and then grow in amplitude and complexity as the acceleration amplitude of the diaphragm is slowly increased from zero. When the acceleration of the diaphragm rises above a well-defined critical value, small secondary droplets begin to be ejected from the free-surface wave crests. Then, quite suddenly, the entire volume of the drop is ejected from the vibrating diaphragm in the form of a spray. This event is the result of an interaction between the fluid dynamical process of droplet ejection and the vibrational dynamics of the diaphragm. During droplet ejection, the effective mass of the drop diaphragm system decreases and the resonance frequency of the system increases. If the initial forcing frequency is above the resonance frequency of the system, droplet ejection causes the system to move closer to resonance, which in turn causes more vigorous vibration and faster droplet ejection. This ultimately leads to drop bursting. In this paper, the basic phenomenon of vibration-induced drop atomization and drop bursting will be introduced, demonstrated, and characterized. Experimental results and a simple mathematical model of the process will be presented and used to explain the basic physics of the system.

  12. Experimental Study on Piezoelectric Energy Harvesting from Vortex-Induced Vibrations and Wake-Induced Vibrations

    Directory of Open Access Journals (Sweden)

    Min Zhang

    2016-01-01

    Full Text Available A rigid circular cylinder with two piezoelectric beams attached on has been tested through vortex-induced vibrations (VIV and wake-induced vibrations (WIV by installing a big cylinder fixed upstream, in order to study the influence of the different flow-induced vibrations (FIV types. The VIV test shows that the output voltage increases with the increases of load resistance; an optimal load resistance exists for the maximum output power. The WIV test shows that the vibration of the small cylinder is controlled by the vortex frequency of the large one. There is an optimal gap of the cylinders that can obtain the maximum output voltage and power. For a same energy harvesting device, WIV has higher power generation capacity; then the piezoelectric output characteristics can be effectively improved.

  13. Acoustic determination of cracks in welded joints. [by resonant structural vibration measurements

    Science.gov (United States)

    Baltanoiu, M.; Criciotoiu, E.

    1974-01-01

    The acoustic analysis method permits detection of any cracks that might take place and their manner of propagation. The study deals with the cracks produced in experiments to determine the welding technology for a welded gray cast iron workpiece by using piezoelectric transducers to determine vibration acceleration.

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

    Science.gov (United States)

    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. Measurements of Acoustic Properties of Porous and Granular Materials and Application to Vibration Control

    Science.gov (United States)

    Park, Junhong; Palumbo, Daniel L.

    2004-01-01

    For application of porous and granular materials to vibro-acoustic controls, a finite dynamic strength of the solid component (frame) is an important design factor. The primary goal of this study was to investigate structural vibration damping through this frame wave propagation for various poroelastic materials. A measurement method to investigate the vibration characteristics of the frame was proposed. The measured properties were found to follow closely the characteristics of the viscoelastic materials - the dynamic modulus increased with frequency and the degree of the frequency dependence was determined by its loss factor. The dynamic stiffness of hollow cylindrical beams containing porous and granular materials as damping treatment was measured also. The data were used to extract the damping materials characteristics using the Rayleigh-Ritz method. The results suggested that the acoustic structure interaction between the frame and the structure enhances the dissipation of the vibration energy significantly.

  16. Pedestrian-induced lateral vibrations of footbridges

    DEFF Research Database (Denmark)

    Ingólfsson, Einar Thór; Georgakis, Christos T.; Jönsson, Jeppe

    2012-01-01

    The earliest scientific descriptions of excessive pedestrian-induced lateral vibrations are dated back to the 1970s, but it was not until the beginning of the new millennium that bridge engineers fully comprehended the potential negative effect of pedestrian crowds on long-span footbridges....... Following the unexpected serviceability failures of Paris’ Solférino and London’s Millennium footbridges in 1999 and 2000, a new tract of research was initiated, focused on understanding the phenomenon which has become known as Synchronous Lateral Excitation (SLE). In this paper, a comprehensive review...... of studies related to pedestrian-induced lateral vibrations of footbridges is provided, primarily focusing on studies published within the last decade. Research in this field can generally be split into three categories; (i) fullscale testing of existing bridges subject to crowd loading, (ii) laboratory...

  17. Nonlinear Scattering of Acoustic Waves by Vibrating Obstacles.

    Science.gov (United States)

    1983-06-01

    usual to simplify Eq. (14) under the assumption of adiabatic compressibility. According to Morse & Ingard [41], adiabatic compressibility is achieved...standard 58 acoustic text, such as Morse and Ingard [44]. They are w r cc r P Po[Jo(-R-) + 2 mcosOJa( T) , (107) 0 2ll 0 a D( 1 ) w r i Pscatt Am ) pt...Comments on the Interaction of Sound With Sound," presentation at 98th Mtg. of Acoust. Soc. Am., Nov 1979. 29. P.M. Morse & K.U. Ingard , Theoretical

  18. Impact of acoustic airflow on intrasinus drug deposition: New insights into the vibrating mode and the optimal acoustic frequency to enhance the delivery of nebulized antibiotic

    OpenAIRE

    2015-01-01

    International audience; Aim: We investigated the impact of vibrating acoustic airflow, the high frequency (f ≥ 100 Hz) and the low frequency (f ≤ 45 Hz) sound waves, on the enhancement of intrasinus drug deposition.Methods: 81mKr-gas ventilation study was performed in a plastinated human cast with and without the addition of vibrating acoustic airflow. Similarly, intrasinus drug deposition in a nasal replica using gentamicin as a marker was studied with and without the superposition of differ...

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

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    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.

  1. CFD Simulations of Vibration Induced Droplet Ejection.

    Science.gov (United States)

    James, Ashley; Smith, Marc K.; Glezer, Ari

    1998-11-01

    Vibration-induced droplet ejection is a process that occurs when a liquid droplet is placed on a vibrating membrane. Above a critical value of the excitation amplitude, Faraday waves form on the surface of the drop. As the amplitude is increased secondary drops are ejected from the wave crests. A Navier-Stokes solver designed to simulate the transient fluid mechanics of the process is presented. The solver is based on a MAC method on a staggered grid. A volume of fluid method is implemented to track the free surface. The volume fraction is advected via a second-order, unsplit method that minimizes numerical diffusion of the interface. Surface tension is incorporated as a continuum surface force. This work is intended to provide a comprehensive description of the fluid dynamics involved in vibration-induced droplet ejection, with the aim of understanding the mechanism behind the ejection process. The evolution of the interface through droplet ejection will be simulated. The dependence of the ejection process on the driving parameters will be evaluated and the resonance characteristics of the drop will be determined. The results of the computations will be compared with experimental results.

  2. Machine Fault Detection Based on Filter Bank Similarity Features Using Acoustic and Vibration Analysis

    Directory of Open Access Journals (Sweden)

    Mauricio Holguín-Londoño

    2016-01-01

    Full Text Available Vibration and acoustic analysis actively support the nondestructive and noninvasive fault diagnostics of rotating machines at early stages. Nonetheless, the acoustic signal is less used because of its vulnerability to external interferences, hindering an efficient and robust analysis for condition monitoring (CM. This paper presents a novel methodology to characterize different failure signatures from rotating machines using either acoustic or vibration signals. Firstly, the signal is decomposed into several narrow-band spectral components applying different filter bank methods such as empirical mode decomposition, wavelet packet transform, and Fourier-based filtering. Secondly, a feature set is built using a proposed similarity measure termed cumulative spectral density index and used to estimate the mutual statistical dependence between each bandwidth-limited component and the raw signal. Finally, a classification scheme is carried out to distinguish the different types of faults. The methodology is tested in two laboratory experiments, including turbine blade degradation and rolling element bearing faults. The robustness of our approach is validated contaminating the signal with several levels of additive white Gaussian noise, obtaining high-performance outcomes that make the usage of vibration, acoustic, and vibroacoustic measurements in different applications comparable. As a result, the proposed fault detection based on filter bank similarity features is a promising methodology to implement in CM of rotating machinery, even using measurements with low signal-to-noise ratio.

  3. Pedestrian-induced lateral vibrations of footbridges

    DEFF Research Database (Denmark)

    Ingólfsson, Einar Thór

    The dissertation investigates the phenomenon of excessive pedestrian-induced lateral vibrations as observed on several high-profile footbridges. In particular, the temporary closures of both Paris’ Solferino Bridge (1999) and the London Millennium Bridge (2000) have led to an understanding...... on the part of engineers and architects of the need to evaluate the potential for footbridge vibrations that can be attributed to pedestrians. Within the scientific community, the closures have also led to the initiation of a new tract of research, focused on the understanding of pedestrian loading, bridge...... is presented, solely focused on pedestrianinduced lateral forces, their effect on footbridges and existing theoretical models of humanstructure interaction. It is shown that different hypotheses exist about the nature of this interaction, many of which are only supported by theoretical modelling and lack...

  4. Thermally induced acoustic waves in porous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Gavrilchenko, Iryna V.; Shulimov, Yuriy G.; Skryshevsky, Valeriy A. [Radiophysics Department, Kyiv National Taras Shevchenko University, Kyiv (Ukraine); Benilov, Arthur I. [Radiophysics Department, Kyiv National Taras Shevchenko University, Kyiv (Ukraine); Laboratoire d' Electronique, Optoelectronique et Microsystemes, Ecole Centrale de Lyon, Ecully (France)

    2009-07-15

    Thermally induced acoustic waves in structures with porous silicon have been studied. Two different schemas of acoustic phenomena recording are compared: in the first one a signal from microphone was measured as function of output frequency, in second one the resistance of porous silicon was measured using Wheatstone bridge. For both methods, the resonance peak is situated in same frequencies depending on difference in thermal properties between porous silicon and c-Si as well as geometry of studied structures. 1.0 kHz shifting of resonance peak in saturated alcohol vapors comparing to ambient air is observed. It can be applied as new transducer for chemical sensors based on porous silicon. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

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

    Institute of Scientific and Technical Information of China (English)

    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.

  6. A theoretical study of the vibration and acoustics of ancient Chinese bells.

    Science.gov (United States)

    Jing, M

    2003-09-01

    In this paper, the acoustics of an ancient Chinese bell, which was made some 3000 years B.C., is studied theoretically. In ancient times, a set of the bells was used as a musical instrument. Unlike a western church bell and an ancient Indian bell, an ancient Chinese bell has two interesting acoustics. First, two tones can be heard separately as the bell is struck at two special points. The interval between the two pitches is always a minor or major third. Second, tones of the bell attenuate quickly, which is necessary for a musical instrument. So, an ancient Chinese bell is sometimes called a two-tone bell or a music bell. Although a three-dimensional model should be used to simulate the acoustics of the bell, a simplified model proposed in this paper does give some insight. Based on the lens-shaped cross section of an ancient Chinese bell, two tones of an ancient Chinese bell can be simulated by the vibration of a double-circular arch and the quick attenuation of tones can be simulated by acoustics of a cylinder with the lens-shaped cross section like a double-circular arch. Numerical results on the vibration and acoustics of the models are presented.

  7. Wind induced vibration analysis of composite footbridge

    Directory of Open Access Journals (Sweden)

    Bartosz Sobczyk

    2015-03-01

    Full Text Available In the work, we describe a simplified method for numerical analysis of a FRP composite footbridge in the field of wind induced vibrations. We consider a simply supported structure with a span length of 16 m and U-shape cross-section. Firstly, a two dimensional flow analysis is performed of the fixed bridge cross-section which is subjected to a lateral wind action with 10 m/s velocity. Calculations are performed using ANSYSSYSSYS FLUENT 14 software. Results of the flow analysis (Strouhal’s number are compared with the results presented in a monograph by A. Flaga, entitled Inżynieria Wiatrowa. Podstawy i zastosowania (Wind Engineering. The bases and applications (in Polish, Arkady, Warszawa, 2008, in order to validate calculations. After that, a three dimensional spatial model of the footbridge is built in ABAQUS 6.12-3 finite element method software. A modal dynamics problem is solved, where the loading conditions are adopted on the basis of the flow analysis and applied as an evenly distributed pressure on the bridge deck surface. Finally, the users’ vibration comfort criterion is checked for the considered structure.[b]Keywords[/b]: composite shell footbridge, wind flow, modal method, footbridges vibrations

  8. Vibrational and acoustical characteristics of the piano soundboard

    CERN Document Server

    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 ...

  9. Guidelines for numerical vibration and acoustic analysis of disc brake squeal using simple models of brake systems

    Science.gov (United States)

    Oberst, S.; Lai, J. C. S.; Marburg, S.

    2013-04-01

    Brake squeal has become of increasing concern to the automotive industry but guidelines on how to confidently predict squeal propensity are yet to be established. While it is standard practice to use the complex eigenvalue analysis to predict unstable vibration modes, there have been few attempts to calculate their acoustic radiation. Here guidelines are developed for numerical vibration and acoustic analysis of brake squeal using models of simplified brake systems with friction contact by considering (1) the selection of appropriate elements, contact and mesh; (2) the extraction of surface velocities via forced response; and (3) the calculation of the acoustic response itself. Results indicate that quadratic tetrahedral elements offer the best option for meshing more realistic geometry. A mesh has to be sufficiently fine especially in the contact region to predict mesh-independent unstable vibration modes. Regarding the vibration response, only the direct, steady-state method with a pressurised pad and finite sliding formulation (allowing contact separation) should be used. Comparison of different numerical methods suggest that a obroadband fast multi-pole boundary element method with the Burton-Miller formulation would efficiently solve the acoustic radiation of a full brake system. Results also suggest that a pad lift-off can amplify the acoustic radiation similar to a horn effect. A horn effect is also observed for chamfered pads which are used in practice to reduce the number and strength of unstable vibration modes. These results highlight the importance of optimising the pad shape to reduce acoustic radiation of unstable vibration modes.

  10. COMPLEX HEAT TRANSFER ENHANCEMENT BY FLUID INDUCED VIBRATION

    Institute of Scientific and Technical Information of China (English)

    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.

  11. Probing elasticity at the nanoscale: Terahertz acoustic vibration of small metal nanoparticles.

    Science.gov (United States)

    Juvé, Vincent; Crut, Aurélien; Maioli, Paolo; Pellarin, Michel; Broyer, Michel; Del Fatti, Natalia; Vallée, Fabrice

    2010-05-12

    The acoustic response of surface-controlled metal (Pt) nanoparticles is investigated in the small size range, between 1.3 and 3 nm (i.e., 75-950 atoms), using time-resolved spectroscopy. Acoustic vibration of the nanoparticles is demonstrated, with frequencies ranging from 1.1 to 2.6 THz, opening the way to the development of THz acoustic resonators. The frequencies, measured with a noncontact optical method, are in excellent agreement with the prediction of a macroscopic approach based on the continuous elastic model, together with the bulk material elastic constants. This demonstrates the validity of this model at the nanoscale and the weak impact of size reduction on the elastic properties of a material, even for nanoparticles formed by less than 100 atoms.

  12. Gearbox tooth cut fault diagnostics using acoustic emission and vibration sensors--a comparative study.

    Science.gov (United States)

    Qu, Yongzhi; He, David; Yoon, Jae; Van Hecke, Brandon; Bechhoefer, Eric; Zhu, Junda

    2014-01-14

    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.

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

    Directory of Open Access Journals (Sweden)

    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.

  14. Damping of acoustic vibrations of immobilized single gold nanorods in different environments.

    Science.gov (United States)

    Yu, Kuai; Zijlstra, Peter; Sader, John E; Xu, Qing-Hua; Orrit, Michel

    2013-06-12

    We present measurements of the acoustic vibrations of single gold nanorods deposited on a glass substrate immersed in air and water by ultrafast pump-probe spectroscopy. The nanorods display two vibration modes, the breathing mode and the extensional mode. The damping time of the two modes is influenced by the environment, and a reduction of the quality factor is observed when the particles are immersed in water. The reduced quality factor of the breathing mode is in good agreement with a model that takes into account viscous damping and radiation of sound waves into the medium. The extension mode, however, is heavily damped when the particles are immersed in water, which is attributed to hydrodynamic lubrication forces between the nanoparticle and the glass substrate. Our results identify a new mode of damping in supported nanoparticles and indicate that the immersion medium can have different effects on different modes of vibration.

  15. Bond-selective photoacoustic imaging by converting molecular vibration into acoustic waves.

    Science.gov (United States)

    Hui, Jie; Li, Rui; Phillips, Evan H; Goergen, Craig J; Sturek, Michael; Cheng, Ji-Xin

    2016-03-01

    The quantized vibration of chemical bonds provides a way of detecting specific molecules in a complex tissue environment. Unlike pure optical methods, for which imaging depth is limited to a few hundred micrometers by significant optical scattering, photoacoustic detection of vibrational absorption breaks through the optical diffusion limit by taking advantage of diffused photons and weak acoustic scattering. Key features of this method include both high scalability of imaging depth from a few millimeters to a few centimeters and chemical bond selectivity as a novel contrast mechanism for photoacoustic imaging. Its biomedical applications spans detection of white matter loss and regeneration, assessment of breast tumor margins, and diagnosis of vulnerable atherosclerotic plaques. This review provides an overview of the recent advances made in vibration-based photoacoustic imaging and various biomedical applications enabled by this new technology.

  16. Bond-selective photoacoustic imaging by converting molecular vibration into acoustic waves

    Directory of Open Access Journals (Sweden)

    Jie Hui

    2016-03-01

    Full Text Available The quantized vibration of chemical bonds provides a way of detecting specific molecules in a complex tissue environment. Unlike pure optical methods, for which imaging depth is limited to a few hundred micrometers by significant optical scattering, photoacoustic detection of vibrational absorption breaks through the optical diffusion limit by taking advantage of diffused photons and weak acoustic scattering. Key features of this method include both high scalability of imaging depth from a few millimeters to a few centimeters and chemical bond selectivity as a novel contrast mechanism for photoacoustic imaging. Its biomedical applications spans detection of white matter loss and regeneration, assessment of breast tumor margins, and diagnosis of vulnerable atherosclerotic plaques. This review provides an overview of the recent advances made in vibration-based photoacoustic imaging and various biomedical applications enabled by this new technology.

  17. Coupling of Excitons and Discrete Acoustic Phonons in Vibrationally Isolated Quantum Emitters.

    Science.gov (United States)

    Werschler, Florian; Hinz, Christopher; Froning, Florian; Gumbsheimer, Pascal; Haase, Johannes; Negele, Carla; de Roo, Tjaard; Mecking, Stefan; Leitenstorfer, Alfred; Seletskiy, Denis V

    2016-09-14

    The photoluminescence emission by mesoscopic condensed matter is ultimately dictated by the fine-structure splitting of the fundamental exciton into optically allowed and dipole-forbidden states. In epitaxially grown semiconductor quantum dots, nonradiative equilibration between the fine-structure levels is mediated by bulk acoustic phonons, resulting in asymmetric spectral broadening of the excitonic luminescence. In isolated colloidal quantum dots, spatial confinement of the vibrational motion is expected to give rise to an interplay between the quantized electronic and phononic degrees of freedom. In most cases, however, zero-dimensional colloidal nanocrystals are strongly coupled to the substrate such that the charge relaxation processes are still effectively governed by the bulk properties. Here we show that encapsulation of single colloidal CdSe/CdS nanocrystals into individual organic polymer shells allows for systematic vibrational decoupling of the semiconductor nanospheres from the surroundings. In contrast to epitaxially grown quantum dots, simultaneous quantization of both electronic and vibrational degrees of freedom results in a series of strong and narrow acoustic phonon sidebands observed in the photoluminescence. Furthermore, an individual analysis of more than 200 compound particles reveals that enhancement or suppression of the radiative properties of the fundamental exciton is controlled by the interaction between fine-structure states via the discrete vibrational modes. For the first time, pronounced resonances in the scattering rate between the fine-structure states are directly observed, in good agreement with a quantum mechanical model. The unambiguous assignment of mediating acoustic modes to the observed scattering resonances complements the experimental findings. Thus, our results form an attractive basis for future studies on subterahertz quantum opto-mechanics and efficient laser cooling at the nanoscale.

  18. Vortex-Induced Vibrations of Marine Cables and Structures.

    Science.gov (United States)

    2014-09-26

    10. D.T. Tsahalis, "Vortex-induced Vibrations of a Flexible Cylinder Near a Plane Boundary Exposed to Steady and Wave -Induced Currents," Trans...ASME, J. Energy Resources Tech., Vol. 106, 206- 213, 1984. 11. D.T. Tsahalis, "Vortex-Induced Vibrations Due to Steady and Wave -Induced Currents of a...AD-Ai57 481 VORTEX-INDUCED VIBRATIONS OF MARINE CABLES AND i/i STRUCTURES(U) NAVAL RESEARCH LAB WASHINGTON DC 0 M GRIFFIN 19 JUN 85 NRL-5600

  19. Water Induced Vibration in the NSRRC

    CERN Document Server

    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..

  20. Environmental problems of vibrations induced by railway traffic

    Institute of Scientific and Technical Information of China (English)

    XIA He; CAO Yanmei; De Roeck Guido; Degrande Geert

    2007-01-01

    In this paper, a general review is made on the problems of vibrations of the ground and nearby buildings induced by railway traffic, and on the researches on this sub- ject in theoretical analyses, numerical simulations, and field experiments. The characteristics of ground vibrations induced by railway traffic and their propagation, from the aspects of duration, intensity distribution, vehicle load and speed, are summarized. The vibration influences on the daily life of people, the operation of high-tech devices and the safety of buildings, and the vibration properties of subsoil and buildings adjacent to the underground, ground and elevated railway systems are introduced.

  1. Density-near-zero using the acoustically induced transparency of a Fano acoustic resonator

    KAUST Repository

    Elayouch, A.

    2017-01-05

    We report experimental results of near-zero mass density involving an acoustic metamaterial supporting Fano resonance. For this, we designed and fabricated an acoustic resonator with two closely coupled modes and measured its transmission properties. Our study reveals that the phenomenon of acoustically induced transparency is accompanied by an effect of near-zero density. Indeed, the dynamic effective parameters obtained from experimental data show the presence of a frequency band where the effective mass density is close to zero, with high transmission levels reaching 0.7. Furthermore, we demonstrate that such effective parameters lead to wave guiding in a 90-degrees-bent channel. This kind of acoustic metamaterial can, therefore, give rise to acoustic functions like controlling the wavefront, which may lead to very promising applications in acoustic cloacking or imaging.

  2. Identification of rocket-induced acoustic waves in the ionosphere

    Science.gov (United States)

    Mabie, Justin; Bullett, Terence; Moore, Prentiss; Vieira, Gerald

    2016-10-01

    Acoustic waves can create plasma disturbances in the ionosphere, but the number of observations is limited. Large-amplitude acoustic waves generated by energetic sources like large earthquakes and tsunamis are more readily observed than acoustic waves generated by weaker sources. New observations of plasma displacements caused by rocket-generated acoustic waves were made using the Vertically Incident Pulsed Ionospheric Radar (VIPIR), an advanced high-frequency radar. Rocket-induced acoustic waves which are characterized by low amplitudes relative to those induced by more energetic sources can be detected in the ionosphere using the phase data from fixed frequency radar observations of a plasma layer. This work is important for increasing the number and quality of observations of acoustic waves in the ionosphere and could help improve the understanding of energy transport from the lower atmosphere to the thermosphere.

  3. Vibration Control Induced by Ice of a Jacket Platform

    Institute of Scientific and Technical Information of China (English)

    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.

  4. Remote vibration measurement: a wireless passive surface acoustic wave resonator fast probing strategy.

    Science.gov (United States)

    Friedt, J-M; Droit, C; Ballandras, S; Alzuaga, S; Martin, G; Sandoz, P

    2012-05-01

    Surface acoustic wave (SAW) resonators can advantageously operate as passive sensors which can be interrogated through a wireless link. Amongst the practical applications of such devices, structural health monitoring through stress measurement and more generally vibration characteristics of mechanical structures benefit from the ability to bury such sensors within the considered structure (wireless and battery-less). However, measurement bandwidth becomes a significant challenge when measuring wideband vibration characteristics of mechanical structures. A fast SAW resonator measurement scheme is demonstrated here. The measurement bandwidth is limited by the physical settling time of the resonator (Q/π periods), requiring only two probe pulses through a monostatic RADAR-like electronic setup to identify the sensor resonance frequency and hence stress on a resonator acting as a strain gauge. A measurement update rate of 4800 Hz using a high quality factor SAW resonator operating in the 434 MHz Industrial, Scientific and Medical band is experimentally demonstrated.

  5. Nonlinear thickness-stretch vibration of thin-film acoustic wave resonators

    Science.gov (United States)

    Ji, Xiaojun; Fan, Yanping; Han, Tao; Cai, Ping

    2016-03-01

    We perform a theoretical analysis on nonlinear thickness-stretch free vibration of thin-film acoustic wave resonators made from AlN and ZnO. The third-order or cubic nonlinear theory by Tiersten is employed. Using Green's identify, under the usual approximation of neglecting higher time harmonics, a perturbation analysis is performed from which the resonator frequency-amplitude relation is obtained. Numerical calculations are made. The relation can be used to determine the linear operating range of these resonators. It can also be used to compare with future experimental results to determine the relevant thirdand/or fourth-order nonlinear elastic constants.

  6. Vortex induced vibrations of free span pipelines

    Energy Technology Data Exchange (ETDEWEB)

    Koushan, Kamran

    2009-07-01

    Pipelines from offshore petroleum fields must frequently pass over areas with uneven sea floor. In such cases the pipeline may have free spans when crossing depressions. Hence, if dynamic loads can occur, the free span may oscillate and time varying stresses may give unacceptable fatigue damage. A major source for dynamic stresses in free span pipelines is vortex induced vibrations (VIV) caused by steady current. This effect is in fact dominating on deep water pipelines since wave induced velocities and accelerations will decay with increasing water depth. The challenge for the industry is then to verify that such spans can sustain the influence from the environment throughout the lifetime of the pipeline. The aim of the present project is to improve the understanding of vortex induced vibrations (VIV) of free span pipelines, and thereby improve methods, existing computer programs and guidelines needed for design verification. This will result in more cost effective and reliable offshore pipelines when laid on a very rugged sea floor. VIV for multiple span pipeline is investigated and the dynamical interaction between adjacent spans has been shown. The interaction may lead to increased or decreased response of each spans depending on the current speed and the properties for the two spans. The extension of the contact zone between the spans and sea floor parameters will of course also be important for the interaction effect. The influence from temperature variation on vortex induced vibrations has been demonstrated. The response frequency is influenced through changes in pipe tension and sag. Both increase and decrease of the response frequency may be experienced. Moreover, it is shown that the influence from snaking of the pipe on the temperature effect is small, at least for large diameter pipes. A free span pipeline will necessarily oscillate close to the seabed. The presence of the seabed will therefore have some influences on the ambient flow profile and also

  7. VORTEX INDUCED VIBRATIONS OF FINNED CYLINDERS

    Institute of Scientific and Technical Information of China (English)

    SHA Yong; WANG Yong-xue

    2008-01-01

    This article presents the results of a numerical simulation on the vortex induced vibration of various finned cylinders at low Reynolds number. The non-dimensional, incompressible Navier-Stokes equations and continuity equation were adopted to simulate the fluid around the cylinder. The cylinder (with or without fins) in fluid flow was approximated as a mass-spring system. The fluid-body interaction of the cylinder with fins and uniform flow was numerically simulated by applying the displacement and stress iterative computation on the fluid-body interfaces. Both vortex structures and response amplitudes of cylinders with various arrangements of fins were analyzed and discussed. The remarkable decrease of response amplitude for the additions of Triangle60 fins and Quadrangle45 fins was found to be comparable with that of bare cylinder. However, the additions of Triangle00 fins and Quadrangle00 fins enhance the response amplitude greatly. Despite the assumption of two-dimensional laminar flow, the present study can give a good insight into the phenomena of cylinders with various arrangements of fins.

  8. Strategy for predicting railway-induced vibrations in buildings

    DEFF Research Database (Denmark)

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

    2016-01-01

    for predicting vibrations in nearby buildings in an early stage of the building process. The strategy is based on that there is a fairly good knowledge of the properties of the ground and that some on-site vibration measurements are made. By combining these with finite-element analysis, the vibration level......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...

  9. Preliminary vibration, acoustic, and shock design and test criteria for components on the Lightweight External Tank (LWT)

    Science.gov (United States)

    1981-01-01

    The Space Shuttle LWT is divided into zones and subzones. Zones are designated primarily to assist in determining the applicable specifications. A subzone (general Specification) is available for use when the location of the component is known but component design and weight are not well defined. When the location, weight, and mounting configuration of the component are known, specifications for appropriate subzone weight ranges are available. Along with the specifications are vibration, acoustic, shock, transportation, handling, and acceptance test requirements and procedures. A method of selecting applicable vibration, acoustic, and shock specifications is presented.

  10. Acoustically induced transparency using Fano resonant periodic arrays

    KAUST Repository

    El-Amin, Mohamed

    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.

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

    Directory of Open Access Journals (Sweden)

    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.

  12. Flow-Induced Vibration of Circular Cylindrical Structures

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Shoei-Sheng [Argonne National Lab. (ANL), Argonne, IL (United States). Components Technology Division

    1985-06-01

    Flow-induced vibration is a term to denote those phenomena associated with the response of structures placed in or conveying fluid flow. More specifically, the terra covers those cases in which an interaction develops between fluid-dynamic forces and the inertia, damping or elastic forces in the structures. The study of these phenomena draws on three disciplines: (1) structural mechanics, (2) mechanical vibration, and (3) fluid dynamics. The vibration of circular cylinders subject to flow has been known to man since ancient times; the vibration of a wire at its natural frequency in response to vortex shedding was known in ancient Greece as aeolian tones. But systematic studies of the problem were not made until a century ago when Strouhal established the relationship between vortex shedding frequency and flow velocity for a given cylinder diameter. The early research in this area has beer summarized by Zdravkovich (1985) and Goldstein (1965). Flow-induced structural vibration has been experienced in numerous fields, including the aerospace industry, power generation/transmission (turbine blades, heat exchanger tubes, nuclear reactor components), civil engineering (bridges, building, smoke stacks), and undersea technology. The problems have usually been encountered or created accidentally through improper design. In most cases, a structural or mechanical component, designed to meet specific objectives, develops problems when the undesired effects of flow field have not been accounted for in the design. When a flow-induced vibration problem is noted in the design stage, the engineer has different options to eliminate the detrimental vibration. Unfortunately, in many situations, the problems occur after the components are already in operation; the "fix" usually is very costly. Flow-induced vibration comprises complex and diverse phenomena; subcritical vibration of nuclear fuel assemblies, galloping of transmission lines, flutter of pipes conveying fluid, and whirling

  13. Crowd-induced random vibration of footbridge and vibration control using multiple tuned mass dampers

    Science.gov (United States)

    Li, Quan; Fan, Jiansheng; Nie, Jianguo; Li, Quanwang; Chen, Yu

    2010-09-01

    This paper investigates vibration characteristics of footbridge induced by crowd random walking, and presents the application of multiple tuned mass dampers (MTMD) in suppressing crowd-induced vibration. A single foot force model for the vertical component of walking-induced force is developed, avoiding the phase angle inaccessibility of the continuous walking force. Based on the single foot force model, the crowd-footbridge random vibration model, in which pedestrians are modeled as a crowd flow characterized with the average time headway, is developed to consider the worst vibration state of footbridge. In this random vibration model, an analytic formulation is developed to calculate the acceleration power spectral density in arbitrary position of footbridge with arbitrary span layout. Resonant effect is observed as the footbridge natural frequencies fall within the frequency bandwidth of crowd excitation. To suppress the excessive acceleration for human normal walking comfort, a MTMD system is used to improve the footbridge dynamic characteristics. According to the random vibration model, an optimization procedure, based on the minimization of maximum root-mean-square (rms) acceleration of footbridge, is introduced to determine the optimal design parameters of MTMD system. Numerical analysis shows that the proposed MTMD designed by random optimization procedure, is more effective than traditional MTMD design methodology in reducing dynamic response during crowd-footbridge resonance, and that the proper frequency spacing enlargement will effectively reduce the off-tuning effect of MTMD.

  14. Trial Study of Vibration-Induced Effects on Spontaneous Potential

    Institute of Scientific and Technical Information of China (English)

    SunWeibin; QiuWeiting; HeZhanxiang

    2003-01-01

    Vibratory excitation generates not only reflections and refractions of wave fields on the subsurface interfaces but also electromagnetic waves with different frequencies. In this paper we address the vibration-induced effects on the spontaneous potential field. The effects of controllable vibration on the spontaneous potential field were studied under real field geologic conditions. Experimental data confirmed that the vibration-induced effects on the spontaneous potential field do exist under field conditions. Monitoring records over a long time interval showed that there existed three information zones in the vibration-induced effects on spontaneous potential field:These are the signal-variant zone, the extreme-stable zone and the relaxation-recovery zone. Combined with different well-site data, it was concluded that the time-variant features of the anomalies in the information zones was closely related to the properties of the subsurface liquid (oil and water).

  15. Comparative evaluation of Space Transportation System (STS)-3 flight and acoustic test random vibration response of the OSS-1 payload

    Science.gov (United States)

    On, F. J.

    1983-01-01

    A comparative evaluation of the Space Transportation System (STS)-3 flight and acoustic test random vibration response of the Office of Space Science-1 (OSS-1) payload is presented. The results provide insight into the characteristics of vibroacoustic response of pallet payload components in the payload bay during STS flights.

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

    Institute of Scientific and Technical Information of China (English)

    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.

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

    CERN Document Server

    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...

  18. Reduction of Train-induced Vibrations by using Barriers

    Directory of Open Access Journals (Sweden)

    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.

  19. Attenuation of cryocooler induced vibration in spaceborne infrared payloads

    Science.gov (United States)

    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.

  20. Vortex induced vibrations of pipe in high waves. Field measurements

    Energy Technology Data Exchange (ETDEWEB)

    Hansen Ottesen, N.-E.; Pedersen, B.

    1999-07-01

    Vortex induced vibrations have been measured full scale on an instrumented pipe placed vertically in the crest zone of high and steep waves. The Reynolds numbers were in the range 105 to 106. It was found that the vortex induced vibrations in the wave motion were generated within a reduced velocity range of 4 and 8. The vibrations grew intermittently with the passing waves. The vibrations took place in 2-3 modes simultaneously. One mode, however, dominated over the other. The growths of the VIV using a modal analysis were consistent with a basic correlation length of 3 diameters for a stationary pipe with a linear growth of the correlation length of 10 diameter for each 0.1 diameter amplitude. (au)

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

    Institute of Scientific and Technical Information of China (English)

    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.

  2. Interactions in an acoustic world

    CERN Document Server

    Simaciu, Ion; Borsos, Zoltan; Bradac, Mariana

    2016-01-01

    The present paper aims to complete an earlier paper where the acoustic world was introduced. This is accomplished by analyzing the interactions which occur between the inhomogeneities of the acoustic medium, which are induced by the acoustic vibrations traveling in the medium. When a wave packet travels in a medium, the medium becomes inhomogeneous. The spherical wave packet behaves like an acoustic spherical lens for the acoustic plane waves. According to the principle of causality, there is an interaction between the wave and plane wave packet. In specific conditions the wave packet behaves as an acoustic black hole.

  3. Advances in Forecasting and Prevention of Resonances Between Coolant Acoustical Oscillations and Fuel Rod Vibrations

    Energy Technology Data Exchange (ETDEWEB)

    Proskuryakov, Konstantin Nicolaevich [NPP, NPEI, 14, Krasnokazarmennaya str. Moscow, 111250 (Russian Federation)

    2009-06-15

    To prevent the appearance of the conditions for resonance interaction between the fluid flow and the reactor internals (RI), fuel rod (FR ) and fuel assemblies (FA) it is necessary to de-tune Eigen frequency of coolant pressure oscillations (EFCPO) and natural frequency of mechanical element's oscillations and also of the system which is formed by the comprising of these elements. Other words it is necessary to de-tune acoustic resonance frequency and natural frequencies of RI, FR and FA. While solving these problems it is necessary to have a theoretical and settlement substantiation of an oscillation frequency band of the coolant outside of which there is no resonant interaction with structure vibrations. The presented work is devoted to finding the solution of this problem. There are results of an estimation of width of such band as well as the examples of a preliminary quantitative estimation of Q - factors of coolant acoustic oscillatory circuit formed by the equipment of the NPP. Abnormal growth of intensity of pressure pulsations in a mode with definite value of reactor capacity have been found out by measurements on VVER - 1000 reactor. This phenomenon has been found out casually and its original reason had not been identified. Paper shows that disappearance of this effect could be reached by realizing outlet of EFCPO from so-called, pass bands of frequencies (PBF). PBF is located symmetrical on both parties from frequency of own oscillations of FA. Methods, algorithms of calculations and quantitative estimations are developed for EFCPO, Q and PBF in various modes of operation NPP with VVER-1000. Results of calculations allow specifying area of resonant interaction EFCPO with vibrations of FR, FA and a basket of reactor core. For practical realization of the received results it is offered to make corresponding additions to the design documentation and maintenance instructions of the equipment of the NPP with VVER-1000. The improvement of these documents

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

    Science.gov (United States)

    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.

  5. Floor Vibrations - as Induced and Reduced by Humans

    DEFF Research Database (Denmark)

    Pedersen, Lars

    . The appropriateness and accuracy of this modelling approach is evaluated. Implications of human-floor interaction are studied with focus on the impact of the interaction on the size of vibration levels of human-occupied floors and on the impact on floor dynamic characteristics. The influence of the interaction......The work is a contribution to the problem of modelling human-induced dynamic loads on floors and to the problem of modelling the interaction between stationary crowds of people and a vibrating floor. Experimental investigations are made to examine, update and refine currently available models....... As for dynamic loads focus is placed on heel impact excitation and actions of jumping people causing floor vibrations. As for interaction between stationary humans and the vibrating floor focus is on modelling humans as oscillating spring-mass-damper systems attached to the floor rather than as simple added mass...

  6. Experimental and analytical studies on pedestrian induced footbridge vibrations

    DEFF Research Database (Denmark)

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

    2007-01-01

    This paper presents results from experimental study on human-induced vibrations of three lively footbridges in Reykjavik. The project was funded by the Icelandic Public Roads Administration with two main focus areas; validating the FE-models used at the design stage in terms of dynamic characteri......This paper presents results from experimental study on human-induced vibrations of three lively footbridges in Reykjavik. The project was funded by the Icelandic Public Roads Administration with two main focus areas; validating the FE-models used at the design stage in terms of dynamic...

  7. A Randomized Trial on the Effect of Bone Tissue on Vibration-induced Muscle Strength Gain and Vibration-induced Reflex Muscle Activity

    OpenAIRE

    2014-01-01

    Background: Whole-body vibration (WBV) induces reflex muscle activity and leads to increased muscle strength. However, little is known about the physiological mechanisms underlying the effects of whole-body vibration on muscular performance. Tonic vibration reflex is the most commonly cited mechanism to explain the effects of whole-body vibration on muscular performance, although there is no conclusive evidence that tonic vibration reflex occurs. The bone myoregulation reflex is another neuro...

  8. Vibration, acoustic, and shock design and test criteria for components on the Solid Rocket Boosters (SRB), Lightweight External Tank (LWT), and Space Shuttle Main Engines (SSME)

    Science.gov (United States)

    1984-01-01

    The vibration, acoustics, and shock design and test criteria for components and subassemblies on the space shuttle solid rocket booster (SRB), lightweight tank (LWT), and main engines (SSME) are presented. Specifications for transportation, handling, and acceptance testing are also provided.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  10. Evaluating vehicular-induced bridge vibrations for energy harvesting applications

    Science.gov (United States)

    Reichenbach, Matthew; Fasl, Jeremiah; Samaras, Vasilis A.; Wood, Sharon; Helwig, Todd; Lindenberg, Richard

    2012-04-01

    Highway bridges are vital links in the transportation network in the United States. Identifying possible safety problems in the approximately 600,000 bridges across the country is generally accomplished through labor-intensive, visual inspections. Ongoing research sponsored by NIST seeks to improve inspection practices by providing real-time, continuous monitoring technology for steel bridges. A wireless sensor network with a service life of ten years that is powered by an integrated energy harvester is targeted. In order to achieve the target ten-year life for the monitoring system, novel approaches to energy harvesting for use in recharging batteries are investigated. Three main sources of energy are evaluated: (a) vibrational energy, (b) solar energy, and (c) wind energy. Assessing the energy produced from vehicular-induced vibrations and converted through electromagnetic induction is the focus of this paper. The goal of the study is to process acceleration data and analyze the vibrational response of steel bridges to moving truck loads. Through spectral analysis and harvester modeling, the feasibility of vibration-based energy harvesting for longterm monitoring can be assessed. The effects of bridge conditions, ambient temperature, truck traffic patterns, and harvester position on the power content of the vibrations are investigated. With sensor nodes continually recharged, the proposed real-time monitoring system will operate off the power grid, thus reducing life cycle costs and enhancing inspection practices for state DOTs. This paper will present the results of estimating the vibration energy of a steel bridge in Texas.

  11. Preliminary vibration, acoustic, and shock design and test criteria for components on the SRB, ET, and SSME

    Science.gov (United States)

    1976-01-01

    Specifications for vibration, acoustic and shock design for components and subassemblies on the External Tank (ET), Solid Rocket Booster (SRB), and Space Shuttle Main Engine (SSME). Included are vibration, acoustic, shock, transportation, handling, and acceptance test requirements and procedures. The space shuttle ET, SRB, and SSME have been divided into zones and subzones. Zones are designated primarily to assist in determining the applicable specifications. A subzone (General Specification) is available for use when the location of the component is known but component design and weight are not well defined. When the location, weight, and mounting configuration of the component are known, specifications for appropriate subzone weight ranges are available. Criteria for some specific components are also presented.

  12. Flow-induced vibrations of circular cylindrical structures. [LMFBR

    Energy Technology Data Exchange (ETDEWEB)

    Chen, S.

    1977-06-01

    The problems of flow-induced vibrations of circular cylindrical structures are reviewed. First, the general method of analysis and classification of structural responses are presented. Then, the presentation is broken up along the lines with stationary fluid, parallel flow, and cross flow. Finally, design considerations and future research needs are pointed out. 234 references.

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

    DEFF Research Database (Denmark)

    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...

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

    DEFF Research Database (Denmark)

    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...... of the full equations of motion. The expressions are used to estimate and explain the influence of system parameters....

  15. Flow-induced vibration of circular cylindrical structures

    Energy Technology Data Exchange (ETDEWEB)

    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)

  16. Active tuning of stroke-induced vibrations by tennis players.

    Science.gov (United States)

    Chadefaux, Delphine; Rao, Guillaume; Androuet, Philippe; Berton, Eric; Vigouroux, Laurent

    2016-09-06

    This paper investigates how tennis players control stroke-induced vibration. Its aim is to characterise how a tennis player deals with entering vibration waves or how he/she has the ability to finely adjust them. A specific experimental procedure was designed, based on simultaneously collecting sets of kinematic, vibration and electromyographic data during forehand strokes using various commercial rackets and stroke intensities. Using 14 expert players, a wide range of excitations at spectral and temporal levels were investigated. Energetic and spectral descriptors of stroke-induced vibration occurring at the racket handle and at the player's wrist and elbow were computed. Results indicated that vibrational characteristics are strongly governed by grip force and to a lower extent by the racket properties. Grip force management drives the amount of energy, as well as its distribution, into the forearm. Furthermore, hand-grip can be assimilated to an adaptive filter which can significantly modify the spectral parameters propagating into the player's upper limb. A significant outcome is that these spectral characteristics are as much dependent on the player as on the racket. This contribution opens up new perspectives in equipment manufacture by underlining the need to account for player/racket interaction in the design process.

  17. Acoustic Emissions to Measure Drought-Induced Cavitation in Plants

    Directory of Open Access Journals (Sweden)

    Linus De Roo

    2016-03-01

    Full Text Available Acoustic emissions are frequently used in material sciences and engineering applications for structural health monitoring. It is known that plants also emit acoustic emissions, and their application in plant sciences is rapidly increasing, especially to investigate drought-induced plant stress. Vulnerability to drought-induced cavitation is a key trait of plant water relations, and contains valuable information about how plants may cope with drought stress. There is, however, no consensus in literature about how this is best measured. Here, we discuss detection of acoustic emissions as a measure for drought-induced cavitation. Past research and the current state of the art are reviewed. We also discuss how the acoustic emission technique can help solve some of the main issues regarding quantification of the degree of cavitation, and how it can contribute to our knowledge about plant behavior during drought stress. So far, crossbreeding in the field of material sciences proved very successful, and we therefore recommend continuing in this direction in future research.

  18. Dictums for problem solving and approximation in mathematical acoustics: examples involving low-frequency vibration and radiation.

    Science.gov (United States)

    Pierce, Allan D; Thiam, Amadou G

    2012-03-01

    A sequence of dictums for mathematical acoustics is given representing opinions intended to be regarded as authoritative, but not necessarily universally agreed upon. The dictums are presented in the context of the detailed solution for a class of problems involving the forced vibration of a long cylinder protruding half-way into a half-space bounded by a compliant surface (impedance boundary) characterized by a spring constant. One limiting case corresponds to a cylinder vibrating within an infinite rigid baffle, and another limiting case corresponds to a vibrating cylinder on the compliant surface of an incompressible fluid. The second limiting case is identified as analogous to that of a floating half-submerged cylinder whose vibrations cause water waves to propagate over the surface. Attention is focused on vibrations at very low frequencies. Difficulties with insuring a causal solution are pointed out and dictums are given as to how one overcomes such difficulties. Various approximation techniques are described. The derivations involve application of the theory of complex variables and the method of matched asymptotic expansions, and the results include the apparent entrained mass in the near field of the cylinder and the radiation resistance per unit length experienced by the vibrating cylinder.

  19. Vibration and Acoustic Response of Rectangular Sandwich Plate under Thermal Environment

    Directory of Open Access Journals (Sweden)

    Yuan Liu

    2013-01-01

    Full Text Available In this paper, we focus on the vibration and acoustic response of a rectangular sandwich plate which is subjected to a concentrated harmonic force under thermal environment. The critical buckling temperature is obtained to decide the thermal load. The natural frequencies and modes as well as dynamic responses are acquired by using the analytical formulations based on equivalent non-classical theory, in which the effects of shear deformation and rotational inertia are taken into account. The rise of thermal load decreases the natural frequencies and moves response peaks to the low-frequency range. The specific features of sandwich plates with different formations are discussed subsequently. As the thickness ratio of facing to core increases, the natural frequencies are enlarged, and the response peaks float to the high-frequency region. Raising the Young's modulus of the core can cause the similar trends. The accuracy of the theoretical method is verified by comparing its results with those computed by the FEM/BEM.

  20. Asymptotic modal analysis of a rectangular acoustic cavity excited by wall vibration

    Science.gov (United States)

    Peretti, Linda F.; Dowell, Earl H.

    1992-01-01

    Asymptotic modal analysis, a method that has recently been developed for structural dynamical systems, has been applied to a rectangular acoustic cavity. The cavity had a flexible vibrating portion on one wall, and the other five walls were rigid. Banded white noise was transmitted through the flexible portion (plate) only. Both the location along the wall and the size of the plate were varied. The mean square pressure levels of the cavity interior were computed as a ratio of the result obtained from classical modal analysis to that obtained from asymptotic modal analysis for the various plate configurations. In general, this ratio converged to 1.0 as the number of responding modes increased. Intensification effects were found due to both the excitation location and the response location. The asymptotic modal analysis method was both efficient and accurate in solving the given problem. The method has advantages over the traditional methods that are used for solving dynamics problems with a large number of responding modes.

  1. High Resolution X-ray-Induced Acoustic Tomography

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    Salvado, José; Espírito-Santo, António; Calado, Maria

    2012-01-01

    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. PMID:22969364

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

    Directory of Open Access Journals (Sweden)

    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.

  4. An intelligent sensor array distributed system for vibration analysis and acoustic noise characterization of a linear switched reluctance actuator.

    Science.gov (United States)

    Salvado, José; Espírito-Santo, António; Calado, Maria

    2012-01-01

    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.

  5. Effects of induced vibration modes on droplet sliding phenomena

    Science.gov (United States)

    Mejia, Jose Eduardo; Alvarado, Jorge; Yao, Chun-Wei; Dropwise Condensation Collaboration; Engineered Surfaces Collaboration

    2016-11-01

    An analytical and experimental investigation has been undertaken to understand the effects of induced vibration modes on droplet sliding phenomena. A mathematical model has been postulated which is capable of estimating accurately droplet sliding angles when using hydrophobic and hydrophilic surfaces. The model, which takes into account equilibrium contact angle, contact angle hysteresis, and droplet volume, has been validated using experimental data. The model has been modified to be able to estimate droplet sliding angle when different modes of vibrations are imposed on the surfaces. Experimental results to date reveal that when resonance modes of vibrations are imposed, the droplet sliding angles decrease considerably. The results also indicate that the modified model can be used effectively to relate imposed resonance frequencies to the critical sliding angle of droplets. LSAMP sponsored NSF Fellowship.

  6. Piezoelectric energy harvesting from traffic-induced bridge vibrations

    Science.gov (United States)

    Peigney, Michaël; Siegert, Dominique

    2013-09-01

    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.

  7. Synchrotron x-ray imaging of acoustic cavitation bubbles induced by acoustic excitation

    Science.gov (United States)

    Jung, Sung Yong; Park, Han Wook; Park, Sung Ho; Lee, Sang Joon

    2017-04-01

    The cavitation induced by acoustic excitation has been widely applied in various biomedical applications because cavitation bubbles can enhance the exchanges of mass and energy. In order to minimize the hazardous effects of the induced cavitation, it is essential to understand the spatial distribution of cavitation bubbles. The spatial distribution of cavitation bubbles visualized by the synchrotron x-ray imaging technique is compared to that obtained with a conventional x-ray tube. Cavitation bubbles with high density in the region close to the tip of the probe are visualized using the synchrotron x-ray imaging technique, however, the spatial distribution of cavitation bubbles in the whole ultrasound field is not detected. In this study, the effects of the ultrasound power of acoustic excitation and working medium on the shape and density of the induced cavitation bubbles are examined. As a result, the synchrotron x-ray imaging technique is useful for visualizing spatial distributions of cavitation bubbles, and it could be used for optimizing the operation conditions of acoustic cavitation.

  8. Wind induced deformation and vibration of a Platanus acerifolia leaf

    Institute of Scientific and Technical Information of China (English)

    Chuan-Ping Shao; Ye-Jun Chen; Jian-Zhong Lin

    2012-01-01

    Deformation and vibration of twig-connected single leaf in wind is investigated experimentally.Results show that the Reynolds number based on wind speed and length of leaf blade is a key parameter to the aerodynamic problem.In case the front surface facing the wind and with an increase of Reynolds number,the leaf experiences static deformation,large amplitude and low frequency sway,reconfiguration to delta wing shape,flapping of tips,high frequency vibration of whole leaf blade,recovery of delta wing shape,and twig-leaf coupling vibration.Abrupt changes from one state to another occur at critical Reynolds numbers.In case the back surfacc facing the wind,the large amplitude and low frequency sway does not occur,the recovered delta wing shape is replaced by a conic shape,and the critical Reynolds numbers of vibrations are higher than the ones corresponding to the case with the front surface facing the wind.A pair of ram-horn vortex is observed behind the delta wing shaped leaf.A single vortex is found downstream of the conic shaped leaf.A lift is induced by the vortex,and this lift helps leaf to adjust position and posture,stabilize blade distortion and reduce drag and vibration.

  9. Prediction Model for Vortex-Induced Vibration of Circular Cylinder with Data of Forced Vibration

    Institute of Scientific and Technical Information of China (English)

    PAN Zhi-yuan; CUI Wei-cheng; LIU Ying-zhong

    2007-01-01

    A model based on the data from forced vibration experiments is developed for predicting the vortex-induced vibrations (VIV) of elastically mounted circular cylinders in flow. The assumptions for free and forced vibration tests are explored briefly. Energy equilibrium is taken into account to set up the relationship between the dynamic response of self-excited oscillations and the force coefficients from forced vibration experiments. The gap between these two cases is bridged straightforwardly with careful treatment of key parameters. Given reduced mass m* and material damping ratio ζ of an elastically mounted circular cylinder in flow, the response characteristics such as amplitude, frequency, lock-in range, added mass coefficient, cross-flow fluid force and the corresponding phase angle can be predicted all at once. Instances with different combination of reduced mass and material damping ratio are compared to investigate their effects on VIV. The hysteresis phenomenon can be interpreted reasonably. The predictions and the results from recent experiments carried out by Williamson's group are in rather good agreement.

  10. Optimal energy harvesting from vortex-induced vibrations of cables.

    Science.gov (United States)

    Antoine, G O; de Langre, E; Michelin, S

    2016-11-01

    Vortex-induced vibrations (VIV) of flexible cables are an example of flow-induced vibrations that can act as energy harvesting systems by converting energy associated with the spontaneous cable motion into electricity. This work investigates the optimal positioning of the harvesting devices along the cable, using numerical simulations with a wake oscillator model to describe the unsteady flow forcing. Using classical gradient-based optimization, the optimal harvesting strategy is determined for the generic configuration of a flexible cable fixed at both ends, including the effect of flow forces and gravity on the cable's geometry. The optimal strategy is found to consist systematically in a concentration of the harvesting devices at one of the cable's ends, relying on deformation waves along the cable to carry the energy towards this harvesting site. Furthermore, we show that the performance of systems based on VIV of flexible cables is significantly more robust to flow velocity variations, in comparison with a rigid cylinder device. This results from two passive control mechanisms inherent to the cable geometry: (i) the adaptability to the flow velocity of the fundamental frequencies of cables through the flow-induced tension and (ii) the selection of successive vibration modes by the flow velocity for cables with gravity-induced tension.

  11. Optimal energy harvesting from vortex-induced vibrations of cables

    Science.gov (United States)

    Antoine, G. O.; de Langre, E.; Michelin, S.

    2016-11-01

    Vortex-induced vibrations (VIV) of flexible cables are an example of flow-induced vibrations that can act as energy harvesting systems by converting energy associated with the spontaneous cable motion into electricity. This work investigates the optimal positioning of the harvesting devices along the cable, using numerical simulations with a wake oscillator model to describe the unsteady flow forcing. Using classical gradient-based optimization, the optimal harvesting strategy is determined for the generic configuration of a flexible cable fixed at both ends, including the effect of flow forces and gravity on the cable's geometry. The optimal strategy is found to consist systematically in a concentration of the harvesting devices at one of the cable's ends, relying on deformation waves along the cable to carry the energy towards this harvesting site. Furthermore, we show that the performance of systems based on VIV of flexible cables is significantly more robust to flow velocity variations, in comparison with a rigid cylinder device. This results from two passive control mechanisms inherent to the cable geometry: (i) the adaptability to the flow velocity of the fundamental frequencies of cables through the flow-induced tension and (ii) the selection of successive vibration modes by the flow velocity for cables with gravity-induced tension.

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

    OpenAIRE

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

    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 ...

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

    Science.gov (United States)

    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.

  14. Optimal Energy Harvesting from Vortex-Induced Vibrations of Cables

    CERN Document Server

    Antoine, G O; Michelin, S

    2016-01-01

    Vortex-induced vibrations (VIV) of flexible cables are an example of flow-induced vibrations that can act as energy harvesting systems by converting energy associated with the spontaneous cable motion into electricity. This work investigates the optimal positioning of the harvesting devices along the cable, using numerical simulations with a wake oscillator model to describe the unsteady flow forcing. Using classical gradient-based optimization, the optimal harvesting strategy is determined for the generic configuration of a flexible cable fixed at both ends, including the effect of flow forces and gravity on the cable's geometry. The optimal strategy is found to consist systematically in a concentration of the harvesting devices at one of the cable's ends, relying on deformation waves along the cable to carry the energy toward this harvesting site. Furthermore, we show that the performance of systems based on VIV of flexible cables is significantly more robust to flow velocity variations, in comparison with ...

  15. A Nonlinear Vortex Induced Vibration Model of Marine Risers

    Institute of Scientific and Technical Information of China (English)

    LIU Juan; HUANG Weiping

    2013-01-01

    With the exploitation of oil and gas in deep water,the traditional vortex induced vibration (VIV) theory is challenged by the unprecedented flexibility of risers.A nonlinear time-dependent VIV model is developed in this paper based on a VIV lift force model and the Morison equation.Both the inline vibration induced by the flow due to vortex shedding and the fluid-structure interaction in the transverse direction are included in the model.One of the characteristics of the model is the response-dependent lift force with nonlinear damping,which is different from other VIV models.The calculations show that the model can well describe the VIV of deepwater risers with the results agreeing with those calculated by other models.

  16. Image reconstruction with acoustic radiation force induced shear waves

    Science.gov (United States)

    McAleavey, Stephen A.; Nightingale, Kathryn R.; Stutz, Deborah L.; Hsu, Stephen J.; Trahey, Gregg E.

    2003-05-01

    Acoustic radiation force may be used to induce localized displacements within tissue. This phenomenon is used in Acoustic Radiation Force Impulse Imaging (ARFI), where short bursts of ultrasound deliver an impulsive force to a small region. The application of this transient force launches shear waves which propagate normally to the ultrasound beam axis. Measurements of the displacements induced by the propagating shear wave allow reconstruction of the local shear modulus, by wave tracking and inversion techniques. Here we present in vitro, ex vivo and in vivo measurements and images of shear modulus. Data were obtained with a single transducer, a conventional ultrasound scanner and specialized pulse sequences. Young's modulus values of 4 kPa, 13 kPa and 14 kPa were observed for fat, breast fibroadenoma, and skin. Shear modulus anisotropy in beef muscle was observed.

  17. Vortex-Induced Vibrations of a Riser with Design Variations

    Science.gov (United States)

    2016-06-19

    public release; distribution is unlimited 1 Proceedings of the ASME 2016 35 th International Conference on Ocean, Offshore and Arctic Engineering...of Offshore Structures, Berlin: Springer-Verlag. Diana G, Belloli, M, Giappino S, Muggiasca S (2008) “Vortex-Induced Vibrations at High Reynolds...K (2000). “Highly Compliant Rigid Risers: Field Test Benchmarking a Time Domain VIV Algorithm” Proceedings, OTC-11995-MS, Offshore Technology

  18. Heterogeneous Nucleation Induced by Capillary Wave During Acoustic Levitation

    Institute of Scientific and Technical Information of China (English)

    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.

  19. Vibration and acoustic radiation of a finite cylindrical shell submerged at finite depth from the free surface

    Science.gov (United States)

    Guo, Wenjie; Li, Tianyun; Zhu, Xiang; Miao, Yuyue; Zhang, Guanjun

    2017-04-01

    The far-field acoustic radiation of a cylindrical shell with finite length submerged at finite depth from the water surface is studied. Two steps are utilized to solve the problem. The first step is to determine the vibration response of the submerged cylindrical shell by using an analytical method and the second one is to determine the far field sound radiation with the boundary element method. To address the vibration responses of the shell analytically, the cylindrical shell and surrounding fluid are described by the Flügge shell equations and Laplace equation in the cylindrical coordinate system respectively. The free surface effect is taken into consideration by using the image method and the Graf's addition theorem. The reliability and efficiency of the present method are validated by comparison with the finite element method. Then, based on the vibration responses of the shell obtained from the first step, the far-field sound pressure is computed by using the boundary element method. It is found that the vibration of the cylindrical shell submerged at finite depth from the free surface tends to be the same as that in infinite fluid when the submerged depth exceeds a certain value. The frequency and the submerged depth have crucial effects on the fluctuation of the far-field sound pressure, while for the curve of sound pressure level versus immersion depth, the ratio of the distance between the adjacent peak points of sound pressure to the wavelength is independent of the frequency. Moreover, the petal number of the directivity of the far-field sound pressure increases with the increase of the frequency and the submerged depth. The work provides more understanding on the vibration and acoustic radiation behavior of a finite cylindrical shell submerged at finite depth.

  20. Prediction of induced vibrations for a passenger - car ferry

    Science.gov (United States)

    Crudu, L.; Neculet, O.; Marcu, O.

    2016-08-01

    In order to evaluate the ship hull global vibrations, propeller excitation must be properly considered being mandatory to know enough accurate the magnitude of the induced hull pressure impulses. During the preliminary design stages, the pressures induced on the aft part of the ship by the operating propeller can be evaluated based on the guidelines given by the international standards or by the provisions of the Classification Societies. These approximate formulas are taking into account the wake field which, unfortunately, can be only estimated unless experimental towing tank tests are carried out. Another possibility is the numerical evaluation with different Computational Fluid Dynamics (CFD) codes. However, CFD methods are not always easy to be used requiring an accurate description of the hull forms in the aft part of the ship. The present research underlines these aspects during the preliminary prediction of propeller induced vibrations for a double-ended passenger-car ferry propelled by two azimuth fixed pitch thrusters placed at both ends of the ship. The evaluation of the global forced vibration is performed considering the 3D global Finite Element (FE) model, with NX Nastran for Windows. Based on the presented results, the paper provides reliable information to be used during the preliminary design stages.

  1. Prediction of dynamic loads and induced vibrations in stall

    Energy Technology Data Exchange (ETDEWEB)

    Thirstrup Petersen, J.; Aagaard Madsen, H. [Risoe National Lab. (Denmark); Bjoerck, A. [Aeronautical Research Inst. of Sweden (Sweden); Enevoldsen, P. [Bonus Energy A/S (Denmark); Oeye, S. [The Technical Univ. of Denmark (Denmark); Ganander, H. [Teknikgruppen AB (Sweden); Winkelaar, D. [Netherlands Energy Research Foundation (Netherlands)

    1998-05-01

    Results from research in an EC Joule-III project and from national projects are presented. The objectives are improvement of design methods for stall regulated wind turbines with emphasis on stall induced vibrations and dynamic stall. The primary concern is limitation of the edgewise vibrations in the fundamental blade natural mode shape, which have caused trouble on modern wind turbines of approximate size 500 kW nominal power and 40 m rotor diameter. A theoretical study of quasi-steady aerodynamics confirms that the vibrations are driven basically by energy supplied from the aerodynamic forces during stalled operation. This energy exchange is equivalent to negative aerodynamic damping. The theoretical approach identifies the main parameters controlling the phenomenon. These parameters describe the steady and the dynamic airfoil characteristics, the overall aerodynamic layout of the blade, e.g. chord length and twist, the structural properties of the blade, e.g. structural damping and properties controlling the resulting vibration direction. Furthermore, full aeroelastic calculations and comparison with measurements show that the properties of the supporting structure, i.e. the main shaft, the nacelle and the tower, are important, as the global vibration of the rotor on its support may exchange energy with the blade vibration, when the blade natural frequency is close to one of the frequencies of the coupled rotor tilt-yaw mode shapes, usually denoted the global rotor whirl frequencies. It is confirmed that the influence of changing the primary design parameters can be determined by use of qualified aeroelastic calculations. Presented design guidelines therefore build on both the simple quasi-steady models, which can be used for the preliminary choice of the design variables mentioned above, and on full aeroelastic calculations. The aeroelastic calculations refine the design basis and should be used for choosing the final design variables and for final

  2. Full-scale field measurements of wave kinematics and vortex shedding induced vibrations in slender structures

    Energy Technology Data Exchange (ETDEWEB)

    Thomsen, J.R.; Pedersen, B. [LIC Engineering (Denmark); Nielsen, K.G.; Bryndum, M.B. [Dansk Hydraulisk Inst., (Denmark)

    1999-07-01

    Vortex induced vibrations of pipes generated by high and steep waves in the crest zone have been investigated by full-scale field testing, An instrumented cylinder has been suspended from a platform bridge in the North Sea. Adjacent to it a newly developed acoustic system capable of measuring the three dimensional wave kinematics was placed. The kinematics were measured all the way up to the instantaneous water surface elevation, i.e. it included the wave crest. The paper presents time series of measured water surface elevations and orbital velocities at the instantaneous water surface together with the response of the instrumented pipe in a storm. The sea state was measured to H{sub s} {approx_equal} 6.4 m and T{sub z} = 8.4 sec. It was clearly seen that vortex shedding locking-on takes place in some of the rather high modes at the passage of large waves. Intermittent cross flow vortex induced vibrations of between 0.3 diameters up to 0.8 diameters were found in the 8th and the 4th mode respectively. The Reynolds numbers and KC numbers were up to 5 . 10{sup 5} and KC {approx} 250 respectively. (au)

  3. Flow induced vibrations in heat exchangers equipped with helical finned tubes; Stroemungsinduzierte Schwingungen in Spiralrippenrohrbuendelwaermetauschern

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, M.

    2003-08-01

    Flow-induced vibrations resulting from acoustic resonance or fluid-elastic instability cause severe damage to finned-tube heat exchangers. There are hardly any publications on spiral finned tubes. This contribution presents experimental data on intrinsic frequencies and damping of spiral finned tubes as well as equations for calculating intrinsic frequencies. Stability limits for fluid-elastic instabilities were defined in flow experiments. Examples are presented to illustrate the applicability of the calculation method in preventing vibration-induced damage. [German] Stroemungsinduzierte Schwingungen in Rippenrohrwaermetauschern aufgrund von akustischer Resonanz bzw. fluidelastischer Instabilitaet fuehren immer wieder zu schweren Schadensfaellen. Hinsichtlich ihres Schwingungsverhaltens sind Spiralrippenrohre in der Literatur bislang vernachlaessigt worden, obwohl sie in der industriellen Anwendung immer mehr an Bedeutung gewinnen. Im vorliegenden Beitrag werden die Eigenfrequenzen und Daempfungen von Spiralrippenrohren experimentell untersucht und Berechnungsformeln fuer die Eigenfrequenzen angegeben. In Stroemungsexperimenten werden Stabilitaetsgrenzen fuer fluidelastische Instabilitaeten ermittelt. Anhand einiger Beispielfaelle wird aufgezeigt, dass das daraus entwickelte Berechnungsschema zur Absicherung gegen Schwingungsschaeden geeignet ist. (orig.)

  4. Evaluation of Aero Commander sidewall vibration and interior acoustic data: Static operations

    Science.gov (United States)

    Piersol, A. G.; Wilby, E. G.; Wilby, J. F.

    1980-01-01

    Results for the vibration measured at five locations on the fuselage structure during static operations are presented. The analysis was concerned with the magnitude of the vibration and the relative phase between different locations, the frequency response (inertance) functions between the exterior pressure field and the vibration, and the coherent output power functions at interior microphone locations based on sidewall vibration. Fuselage skin panels near the plane of rotation of the propeller accept propeller noise excitation more efficiently than they do exhaust noise.

  5. Experimental validation of a numerical model for subway induced vibrations

    Science.gov (United States)

    Gupta, S.; Degrande, G.; Lombaert, G.

    2009-04-01

    This paper presents the experimental validation of a coupled periodic finite element-boundary element model for the prediction of subway induced vibrations. The model fully accounts for the dynamic interaction between the train, the track, the tunnel and the soil. The periodicity or invariance of the tunnel and the soil in the longitudinal direction is exploited using the Floquet transformation, which allows for an efficient formulation in the frequency-wavenumber domain. A general analytical formulation is used to compute the response of three-dimensional invariant or periodic media that are excited by moving loads. The numerical model is validated by means of several experiments that have been performed at a site in Regent's Park on the Bakerloo line of London Underground. Vibration measurements have been performed on the axle boxes of the train, on the rail, the tunnel invert and the tunnel wall, and in the free field, both at the surface and at a depth of 15 m. Prior to these vibration measurements, the dynamic soil characteristics and the track characteristics have been determined. The Bakerloo line tunnel of London Underground has been modelled using the coupled periodic finite element-boundary element approach and free field vibrations due to the passage of a train at different speeds have been predicted and compared to the measurements. The correspondence between the predicted and measured response in the tunnel is reasonably good, although some differences are observed in the free field. The discrepancies are explained on the basis of various uncertainties involved in the problem. The variation in the response with train speed is similar for the measurements as well as the predictions. This study demonstrates the applicability of the coupled periodic finite element-boundary element model to make realistic predictions of the vibrations from underground railways.

  6. Road vehicle-induced vibration control of microelectronics facilities

    Institute of Scientific and Technical Information of China (English)

    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.

  7. Evaluation of human-induced vibration of continuous footbridges

    Directory of Open Access Journals (Sweden)

    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”.

  8. Interaction of electronic excitations of Tm3+ ions with acoustic vibrations in KTm(MoO4)2

    Science.gov (United States)

    Kamenskyi, D.; Poperezhai, S.; Gogoi, P.; Engelkamp, H.; Maan, J. C.; Wosnitza, J.; Kut'ko, V.

    2014-01-01

    Electron paramagnetic resonance spectra of KTm(MoO4)2 were measured as a function of magnetic field between 3 and 11.5 cm-1 at T =2 K. We found that in addition to the absorption line caused by the electronic excitation of Tm3+ ions, the spectra contain sidebands. Far-infrared transmission measured with polarized light from 10 to 75 cm-1 revealed vibration modes at 16.7 and 25.7 cm-1 for polarizations Eω∥a and Eω∥c, respectively. We show that sidebands in the spectra of paramagnetic resonance result from a parametric resonance between the electronic excitations of the Tm3+ ions and the acoustic vibrations of the crystal lattice.

  9. Influence of Acoustic Coating on Underwater Vibration & Acoustic Characteristic of a Compound Cylindrical & Cone Structure%声学覆盖层对锥柱组合结构水下振动噪声的影响

    Institute of Scientific and Technical Information of China (English)

    缪旭弘; 庞福振

    2011-01-01

    Influence of acoustic coating on the underwater vibration & acoustic characteristic of a compound cylindrical & cone structure (CCCS) is researched based on SEA (Statistical Energy Analysis) method. The result indicates that the arrangement of acoustic coating and damping loss factor of CCCS have significant influence on the capacity of vibration and noise reduction of acoustic coating to the CCCS. Acoustic coating can reduce the vibration and noise level of the CCCS. Vibration reduction effect is remarkable to the downstream structure, but it is neglectable to the upstream if the acoustic coating is arranged on the main stream of vibration transmission. Vibration & noise reduction capacity of acoustic coating is proportional to the covering density. The result also indicates that damping loss coefficient has effect on the noise reduction capacity of the acoustic coating. Noise will leak out from regions uncovered if damping loss coefficient is rather small, which will inevitably decrease the noise reduction capacity of acoustic coating. The "noise leaking" phenomenon is loosening with the increase of damping loss coefficient, while the vibration & noise reduction capacity of acoustic coating decreases.%基于统计能量法研究声学覆盖层对锥柱组合结构水下振动噪声的影响.研究结果表明,覆盖层敷设方式、结构损耗因子对声学覆盖层抑振降噪效果有较大影响,当声学覆盖层敷设在结构振动主导传递途径中时,其对传递途径下游结构的抑振效果较为明显,而对振源及传递途径上游结构的振动影响不大,且其抑振降噪效果随敷设密度的增加而增大;损耗因子较小时,声能将从未敷设区域“泄漏”出来,出现“声泄漏”现象,导致声学覆盖层降噪效果下降;随着损耗因子的不断增大,“声泄漏”现象逐渐得到缓解,但声学覆盖层抑振降噪效果有所下降.

  10. Preliminary vibration, acoustic, and shock design and test criteria for components on the HEAO-A spacecraft

    Science.gov (United States)

    1975-01-01

    These vibration, acoustic, and shock specifications provide the qualification test criteria for spacecraft components and subassemblies and for the High Energy Astronomy Observatory (HEAO-A) experiments. The HEAO-A was divided into zones and subzones to obtain simple component groupings. Zones are designated primarily to assist in determining the applicable specification. A Subzone is available for use when the location of the component is known but component design and weight are not well defined. When the location, weight, and mounting configuration of the component are known, the appropriate Subzone weight ranges are available. Experiment and specific component specifications are available.

  11. Preliminary vibration, acoustic, and shock design and test criteria for components on the HEAO-C spacecraft

    Science.gov (United States)

    1975-01-01

    The vibration, acoustic, and shock specification test criteria for spacecraft components and subassemblies and for the high Energy Astronomy Observatory (HEAO-C) experiments are presented. The HEAO-C was divided into zones and subzones to obtain simple component groupings. Zones are designated primarily to assist in determining the applicable specification. A subzone (general specification) is available for use when the location of the component is known but component design and weight are not well defined. When the location, weight, and mounting configuration of the component are known, the appropriate subzone weight ranges (-A, -B, etc. ) are available. Experiment and specific component specifications are available.

  12. Energy harvesting using vortex-induced vibrations of tensioned cables

    CERN Document Server

    Grouthier, Clement; de Langre, Emmanuel

    2012-01-01

    The development of energy harvesting systems based on fluid/structure interactions is part of the global search for innovative tools to produce renewable energy. In this paper, the possibility to harvest energy from a flow using vortex-induced vibrations (VIV) of a tensioned flexible cable is analyzed. The fluid loading on the vibrating solid and resulting dynamics are computed using an appropriate wake-oscillator model, allowing one to perform a systematic parametric study of the efficiency. The generic case of an elastically-mounted rigid cylinder is first investigated, before considering an infinite cable with two different types of energy harvesting : a uniformly spanwise distributed harvesting and then a periodic distribution of discrete harvesting devices. The maximum harvesting efficiency is of the same order for each configuration and is always reached when the solid body and its wake are in a frequency lock-in state.

  13. Spray characterization during vibration-induced drop atomization

    Science.gov (United States)

    Vukasinovic, Bojan; Smith, Marc K.; Glezer, Ari

    2004-02-01

    Vibration-induced drop atomization is a process of rapid droplet ejection from a larger liquid drop. This occurs when a liquid drop resting on a thin diaphragm is vibrated under the appropriate forcing conditions using an attached piezoelectric actuator. The resulting spray of small droplets is characterized in this work using high-speed imaging and particle-tracking techniques. The results show that the average spatial and velocity distributions of the spray droplets are fairly axisymmetric during all stages of the atomization. The mean diameter of the droplets depends on the forcing frequency to the -2/3 power. The ejection velocity of the spray droplets depends on both the magnitude and the rate of change of the forcing amplitude. Thus, controlling the characteristics of the forcing signal may lead to strategies for controlling the spray process in specific applications.

  14. Laser-induced vibration of a thin soap film.

    Science.gov (United States)

    Emile, Olivier; Emile, Janine

    2014-09-21

    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 employed in an optofluidic diaphragm pump, the interfaces behaving like a vibrating membrane and the liquid in-between being the fluid to be pumped. Such a pump could then be used in delicate micro-equipment, in chips where temperature variations are detrimental and even in biological systems.

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

    Directory of Open Access Journals (Sweden)

    Gu Wenbin

    2015-01-01

    Full Text Available 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 drilling blasting was measured in a field experiment. It shows that the water bottom vibration monitor could collect vibration signals quite effectively in underwater environments. The followed signal analysis shows that the characteristics of water bottom vibration and land ground vibration induced by the same underwater drilling blasting are quite different due to the different geological environments. The amplitude and frequency band of water bottom vibration both exceed those of land ground vibration. Water bottom vibration is mainly in low-frequency band that induced by blasting impact directly acts on rock. Besides the low-frequency component, land vibration contains another higher frequency band component that induced by followed water hammer wave acts on bank slope.

  16. Current-induced runaway vibrations in dehydrogenated graphene nanoribbons

    DEFF Research Database (Denmark)

    Christensen, Rasmus Bjerregaard; Lu, Jing Tao; Hedegard, Per;

    2016-01-01

    We employ a semi-classical Langevin approach to study current-induced atomic dynamics in a partially dehydrogenated armchair graphene nanoribbon. All parameters are obtained from density functional theory. The dehydrogenated carbon dimers behave as effective impurities, whose motion decouples from...... the rest of carbon atoms. The electrical current can couple the dimer motion in a coherent fashion. The coupling, which is mediated by nonconservative and pseudo-magnetic current-induced forces, change the atomic dynamics, and thereby show their signature in this simple system. We study the atomic dynamics...... and current-induced vibrational instabilities using a simplified eigen-mode analysis. Our study illustrates how armchair nanoribbons can serve as a possible testbed for probing the current-induced forces....

  17. Current-induced runaway vibrations in dehydrogenated graphene nanoribbons

    Directory of Open Access Journals (Sweden)

    Rasmus Bjerregaard Christensen

    2016-01-01

    Full Text Available We employ a semi-classical Langevin approach to study current-induced atomic dynamics in a partially dehydrogenated armchair graphene nanoribbon. All parameters are obtained from density functional theory. The dehydrogenated carbon dimers behave as effective impurities, whose motion decouples from the rest of carbon atoms. The electrical current can couple the dimer motion in a coherent fashion. The coupling, which is mediated by nonconservative and pseudo-magnetic current-induced forces, change the atomic dynamics, and thereby show their signature in this simple system. We study the atomic dynamics and current-induced vibrational instabilities using a simplified eigen-mode analysis. Our study illustrates how armchair nanoribbons can serve as a possible testbed for probing the current-induced forces.

  18. Experimental chaotic quantification in bistable vortex induced vibration systems

    Science.gov (United States)

    Huynh, B. H.; Tjahjowidodo, T.

    2017-02-01

    The study of energy harvesting by means of vortex induced vibration systems has been initiated a few years ago and it is considered to be potential as a low water current energy source. The energy harvester is realized by exposing an elastically supported blunt structure under water flow. However, it is realized that the system will only perform at a limited operating range (water flow) that is attributed to the resonance phenomenon that occurs only at a frequency that corresponds to the fluid flow. An introduction of nonlinear elements seems to be a prominent solution to overcome the problem. Among many nonlinear elements, a bistable spring is known to be able to improve the harvested power by a vortex induced vibrations (VIV) based energy converter at the low velocity water flows. However, it is also observed that chaotic vibrations will occur at different operating ranges that will erratically diminish the harvested power and cause a difficulty in controlling the system that is due to the unpredictability in motions of the VIV structure. In order to design a bistable VIV energy converter with improved harvested power and minimum negative effect of chaotic vibrations, the bifurcation map of the system for varying governing parameters is highly on demand. In this study, chaotic vibrations of a VIV energy converter enhanced by a bistable stiffness element are quantified in a wide range of the governing parameters, i.e. damping and bistable gap. Chaotic vibrations of the bistable VIV energy converter are simulated by utilization of a wake oscillator model and quantified based on the calculation of the Lyapunov exponent. Ultimately, a series of experiments of the system in a water tunnel, facilitated by a computer-based force-feedback testing platform, is carried out to validate the existence of chaotic responses. The main challenge in dealing with experimental data is in distinguishing chaotic response from noise-contaminated periodic responses as noise will smear

  19. Cross flow induced vibrations in staggered arrays of cylindrical structures

    Energy Technology Data Exchange (ETDEWEB)

    Marn, J.

    1991-12-31

    Flow induced vibrations cause by instability is the subject of this investigation. The bulk of the work performed is theoretical in nature, the comparison with some of existing experimental data is given for each of four models described. First model encompasses the effects of prescribed motion on the cylinder. Such circumstances occur in the case of vortex shedding initiated instability. The reduced velocity within the cylinder array is low and there is no coupling between the adjacent cylinders. Second model assumes certain form of vibration and corresponding behavior of the perturbed velocity field in temporal and one of spatial coordinates thus transforming partial differential equations into ordinary differential equations and takes into account the motion of the neighboring cylinder. This corresponds to fluid elastic controlled instabilities. The resulting equations are solved analytically. The model is used for better understanding of the equations of cylinder motion as well as for quick estimates of threshold of instability. Third model relaxes an assumption about the form of vibration in spatial direction and uses the vorticity formulation of equation of fluid motion to account for fluid-solid interaction. This model analysis is of two phase (air-water mixture) flow. The void fraction distribution is found to be the single most decisive factor to determine the onset of instability for such a domain. In conclusion, two distinct mechanism were found to be responsible for flow induced vibration caused instabilities, (1) outside source controlled periodic excitation (such as vortex shedding) -- described by the first model and (2) fluid elastic forces -- described by second, third and fourth models. For the values of reduced velocity below 0.7 first model is proposed, for the values above 0.7, the rest.

  20. The Shock and Vibration Bulletin. Part 2. Measurement Techniques and Data Analysis, Dynamic Measurements, Vibration and Acoustics

    Science.gov (United States)

    1980-09-01

    DAMPING M. M. Wallace and C. W. Bert, The University of Oklahoma, Norman, OK CONTRIBUTIONS TO THE DYNAMIC ANALYSIS OF MAGLEV VEHICLES ON ELEVATED GUIDEWAYS...state transmitted and/oT reflected sound pressure for a coated, submerged flat plate, subject to a train of normally incident harmonic waves...simply make the length of the train of waves as long as you please. It is in 3i07 Main, I, G , Vibrations and Waves in the low frequency problems

  1. Flow induced vibrations in arrays of irregularly spaced cylinders

    Science.gov (United States)

    Taub, Gordon; Michelin, Sébastien

    2014-11-01

    Historically the main industrial applications of cylinder arrays in cross flows favored regular arrangements of cylinders. For this reason, most past studies of Flow Induced Vibrations (FIV) in large cylinder arrays have focused on such arrangements. Recently there has been some interest in generating renewable energy using FIV of bluff bodies. In such applications it will likely be beneficial to enhance, rather than suppress FIV. It is not known a priori if regular or irregularly spaced arrays are most adequate for this type of application. In this study, wind tunnel experiments were conducted on one regularly spaced array and four different irregularly spaced arrays of cylinders in a cross flow. Each arrangement of cylinders was examined under eight different orientations to a cross flow ranging between 10 m/s and 17 m/s. The average amplitude of vibration of the cylinders was found to highly depend on arrangement and orientation. The typical amplitude of vibration of the rods in the irregular arrangements were found to be an order of magnitude larger than that of the regular array. A simple model was proposed in order to predict if a given arrangement was likely to produce large oscillations, and the validity of the model was examined. This research was supported by a Marie Curie International Reintegration Grant within the 7th European Community Framework Program (Grant PIRG08-GA-2010-276762).

  2. An Experimental Investigation of Vibration-Induced Single Droplet Ejection.

    Science.gov (United States)

    Range, Kai; Smith, Marc K.; Glezer, Ari

    1998-11-01

    Vibration-induced droplet atomization occurs when small secondary droplets are ejected from the free surface of a larger droplet placed on a vibrating membrane. To model a single ejection event, a liquid droplet is placed on a small piston and vibrated using an electromagnetic driver. The droplet oscillates in a characteristic mode shape that depends on the driving frequency and amplitude, the properties of the liquid, and the size of the droplet. When the excitation amplitude is large enough, a small secondary droplet is ejected from the primary droplet. Observations of this process using high-speed digital video imaging show that droplet ejection occurs when a small liquid column or jet appears on the primary droplet and a secondary droplet forms on the column by a capillary-pinching mechanism. The liquid column or jet emanates from a crater in the primary droplet. As the driving frequency increases, this crater becomes smaller and the diameter of the ejected droplet decreases. We shall present results showing how the ejected droplet diameter and speed depends on the driving frequency and amplitude, the liquid properties, and the primary droplet volume.

  3. An Experimental Investigation of Vibration Induced Droplet Atomization*

    Science.gov (United States)

    Vukasinovic, Bojan; Smith, Marc K.; Glezer, Ari

    1999-11-01

    The atomization of a millimeter-scale liquid droplet placed on a vibrating diaphragm is investigated experimentally using high-speed imaging and particle-tracking techniques. Atomization is the result of the rapid ejection of small secondary droplets from the wave crests of a hierarchy of forced surface waves on the primary droplet. The evolution and rate of ejection depend on the coupled dynamics of the primary droplet and the vibrating diaphragm. The present data indicate that secondary droplet ejection results from the collapse of surface craters formed during the evolution of capillary surface waves on the primary droplet. The collapse of the crater and the ensuing ejection of a momentary liquid jet are similar to ejection processes at free surfaces that are induced by the bursting of gas bubbles or the impingement of liquid droplets. The spray characteristics of the ejected droplets are investigated over a broad range of vibrating frequencies (up to 14 kHz) using particle-tracking velocimetry. * Supported by NASA Microgravity Res. Div., Grant NAG3-1949.

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

    CERN Document Server

    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.

  5. Vibration impact acoustic emission technique for identification and analysis of defects in carbon steel tubes: Part B Cluster analysis

    Energy Technology Data Exchange (ETDEWEB)

    Halim, Zakiah Abd [Universiti Teknikal Malaysia Melaka (Malaysia); Jamaludin, Nordin; Junaidi, Syarif [Faculty of Engineering and Built, Universiti Kebangsaan Malaysia, Bangi (Malaysia); Yahya, Syed Yusainee Syed [Universiti Teknologi MARA, Shah Alam (Malaysia)

    2015-04-15

    Current steel tubes inspection techniques are invasive, and the interpretation and evaluation of inspection results are manually done by skilled personnel. Part A of this work details the methodology involved in the newly developed non-invasive, non-destructive tube inspection technique based on the integration of vibration impact (VI) and acoustic emission (AE) systems known as the vibration impact acoustic emission (VIAE) technique. AE signals have been introduced into a series of ASTM A179 seamless steel tubes using the impact hammer. Specifically, a good steel tube as the reference tube and four steel tubes with through-hole artificial defect at different locations were used in this study. The AEs propagation was captured using a high frequency sensor of AE systems. The present study explores the cluster analysis approach based on autoregressive (AR) coefficients to automatically interpret the AE signals. The results from the cluster analysis were graphically illustrated using a dendrogram that demonstrated the arrangement of the natural clusters of AE signals. The AR algorithm appears to be the more effective method in classifying the AE signals into natural groups. This approach has successfully classified AE signals for quick and confident interpretation of defects in carbon steel tubes.

  6. Vortex-induced vibration of a slender single-span cylinder

    NARCIS (Netherlands)

    Oikou, N.

    2014-01-01

    The goal of this paper is to study the vortex-induced vibration of slender cylindrical structures. For this purpose, a 2D model that calculates the coupled cross-flow and in-line vibrations of a flexible single span beam is developed. A wake oscillator known to match well with free vibration experim

  7. Enhancement of channel wall vibration due to acoustic excitation of an internal bubbly flow

    NARCIS (Netherlands)

    Zhang, M.M.; Katz, J.; Prosperetti, A.

    2010-01-01

    The effect of an internal turbulent bubbly flow on vibrations of a channel wall is investigated experimentally and theoretically. Our objective is to determine the spectrum and attenuation rate of sound propagating through a bubbly liquid flow in a channel, and connect these features with the vibrat

  8. Flow Induced Vibration Program at Argonne National Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    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.

  9. Flow-induced Noise and Vibration Analysis of a Piping Elbow with/without a Guide Vane

    Institute of Scientific and Technical Information of China (English)

    Tao Zhang; Yongou Zhang; Huajiang Ouyang; Tao Guo

    2014-01-01

    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.

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

    Science.gov (United States)

    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.

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

    CERN Document Server

    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...

  12. Pattern Matching of Harmonic Vibrations in Nonlinearly Generated Acoustic Modes in Bovine Bone Samples

    Science.gov (United States)

    Alippi, A.; Biagioni, A.; Germano, M.; Passeri, D.

    2008-06-01

    Local probing of nonlinear generation of harmonic vibrations has been done on bone plate samples and the evaluation of the nonlinear term is derived from a limited number of cases of bovine thigh bones, that shows that a low level of nonlinearity is present in bone structures. This is consistent with the assumption that in low level nonlinear samples the distribution of harmonic vibrations matches the corresponding power distribution of the fundamental mode.

  13. Ejection Dynamics in Vibration-Induced Droplet Atomization

    Science.gov (United States)

    Vukasinovic, Bojan; Smith, Marc K.; Glezer, Ari

    2001-11-01

    A primary sessile liquid drop is atomized into a fine spray of secondary droplets using vibration-induced atomization (VIDA) resulting from forced waves on a free surface of the primary drop. The mechanism of free surface breakup during the VIDA process is investigated using high-speed imaging and laser vibrometry. Secondary droplets result from a localized collapse of surface troughs and the ejection and ultimate breakup of momentary liquid spikes. The characteristic breakup time of these liquid spikes scales with the vibration period and the spike length initially varies like t0.5. The breakup begins with a capillary pinch-off from the tip of the spike that can be followed by additional pinching of liquid droplets. For relatively low-viscosity liquid (e.g., water) a capillary-wave instability of a jet is observed in some cases, while in very viscous liquid (e.g., glycerin-water solution) the first breakup occurs near the stem of the jet. The mechanisms of secondary droplet ejection and the influence of the operating parameters and fluid properties are discussed.

  14. Measurement Of Flow Induced Vibration Of Reactor Component

    Science.gov (United States)

    Dharmaraju, N.; Meher, K. K.; Rao, A. Rama

    The effect of flow-induced vibration on class I components in the reactor is a very important design factor for its qualifications worthy of loading inside the core. In this regard, a clear definition of the flow excitation and the dynamic characteristics of the component are the two primary inputs required to make an estimation of vibration severity. Though there are general guidelines available, more often it has been seen that they only help in arriving at a first approximation. There are many instances wherein a component has failed to perform as per design in spite of sufficient margin provided in the calculations. There are also instances wherein some components have failed even after successful testing under close to simulated flow condition. The paper deals with qualification procedure followed to flow test an in core component in an out of pile facility. The adopted procedure is considered to be a best approach especially in this field where in there are many gray areas.

  15. Light-induced vibration in the hearing organ.

    Science.gov (United States)

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

    2014-08-04

    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 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. This shows that the active process is neither local nor instantaneous, but requires mechanical waves traveling from the cochlear base toward its apex. A physiologically-based mathematical model shows that such waves engage the active process, enhancing hearing sensitivity.

  16. Train induced vibrations in geosynthetic reinforced railway embankments

    DEFF Research Database (Denmark)

    Zania, Varvara; Hededal, Ole; Krogsbøll, Anette

    2011-01-01

    includes usually the application of stabilization techniques like geosynthetic reinforcement. Hence, in the current study the ground vibration, which is induced by a train passage in geosynthetic reinforced embankments, is investigated. In addition the impact of the soil conditions is examined. In order...... to accomplish the aforementioned research goals, dynamic finite element analyses of two-dimensional plane strain models have been performed. The results of the adopted approach, which is rather simplified, were compared with the corresponding results reported in the literature for a real scale experiment....... The quite satisfactory agreement of the results provided an acceptable validation of the numerical procedure. This enabled the parametric investigation for analyzing the effect of the characteristic parameters of the subsoil conditions. The results indicate that the impact of the site conditions...

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

    Directory of Open Access Journals (Sweden)

    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.

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

    Science.gov (United States)

    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.

  19. Utilization of old vibro-acoustic measuring equipment to grasp basic concepts of vibration measurements

    DEFF Research Database (Denmark)

    Darula, Radoslav

    2013-01-01

    The aim of the paper is to show that even old vibro-acoustic (analog) equipment can be used as a very suitable teaching equipment to grasp basic principles of measurements in an era, when measurement equipments are more-or-less treated as ‘black-boxes’, i.e. the user cannot see directly how...

  20. Mechanical impedance and acoustic mobility measurement techniques of specifying vibration environments

    Science.gov (United States)

    Kao, G. C.

    1973-01-01

    Method has been developed for predicting interaction between components and corresponding support structures subjected to acoustic excitations. Force environments determined in spectral form are called force spectra. Force-spectra equation is determined based on one-dimensional structural impedance model.

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

    Science.gov (United States)

    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.

  2. Vibration impact acoustic emission technique for identification and analysis of defects in carbon steel tubes: Part A Statistical analysis

    Energy Technology Data Exchange (ETDEWEB)

    Halim, Zakiah Abd [Universiti Teknikal Malaysia Melaka (Malaysia); Jamaludin, Nordin; Junaidi, Syarif [Faculty of Engineering and Built, Universiti Kebangsaan Malaysia, Bangi (Malaysia); Yahya, Syed Yusainee Syed [Universiti Teknologi MARA, Shah Alam (Malaysia)

    2015-04-15

    Current steel tubes inspection techniques are invasive, and the interpretation and evaluation of inspection results are manually done by skilled personnel. This paper presents a statistical analysis of high frequency stress wave signals captured from a newly developed noninvasive, non-destructive tube inspection technique known as the vibration impact acoustic emission (VIAE) technique. Acoustic emission (AE) signals have been introduced into the ASTM A179 seamless steel tubes using an impact hammer, and the AE wave propagation was captured using an AE sensor. Specifically, a healthy steel tube as the reference tube and four steel tubes with through-hole artificial defect at different locations were used in this study. The AE features extracted from the captured signals are rise time, peak amplitude, duration and count. The VIAE technique also analysed the AE signals using statistical features such as root mean square (r.m.s.), energy, and crest factor. It was evident that duration, count, r.m.s., energy and crest factor could be used to automatically identify the presence of defect in carbon steel tubes using AE signals captured using the non-invasive VIAE technique.

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

    Science.gov (United States)

    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.

  4. Hybrid isolation of micro vibrations induced by reaction wheels

    Science.gov (United States)

    Lee, Dae-Oen; Park, Geeyong; Han, Jae-Hung

    2016-02-01

    As the technology for precision satellite payloads continues to advance, the requirements for the pointing stability of the satellites are becoming extremely high. In many situations, even small amplitude disturbances generated by the onboard components may cause serious degradation in the performance of high precision payloads. In such situations, vibration isolators can be installed to reduce the vibration transmission. In this work, a hybrid vibration isolator comprising passive and active components is proposed to provide an effective solution to the vibration problems caused by the reaction wheel disturbances. Firstly, mathematical modeling and experimental study of a single axis vibration isolator having high damping and high roll-off rate for the high frequency region and active components that enhance isolation performance for narrow frequency bands are presented. This concept is then extended to multi-axis by forming Stewart platform and the performance is experimentally verified. The tests on a flexible testbed show effective vibration isolation by the proposed vibration isolator.

  5. Effect of electron heating on femtosecond laser-induced coherent acoustic phonons in noble metals

    Science.gov (United States)

    Wang, Jincheng; Guo, Chunlei

    2007-05-01

    We employ a surface plasmon technique to resolve the dynamics of femtosecond-laser-induced coherent acoustic phonons in noble metals. Clear acoustic oscillations are observed in our experiments. We further study the dependence of the initial phase of the oscillations on pump fluence, and we find that the initial phase decreases linearly with pump fluence. Our model calculations show that hot electrons instantaneously excited by femtosecond pulses contribute to the generation of coherent acoustic phonons in metals.

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

    DEFF Research Database (Denmark)

    Muller, Peter Barkholt; Bruus, Henrik

    2015-01-01

    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...

  7. The effects of pre-exercise vibration stimulation on the exercise-induced muscle damage

    Science.gov (United States)

    Kim, Ji-Yun; Kang, Da-Haeng; Lee, Joon-Hee; O, Se-Min; Jeon, Jae-Keun

    2017-01-01

    [Purpose] To investigate the effects of pre-induced muscle damage vibration stimulation on the pressure-pain threshold and muscle-fatigue-related metabolites of exercise-induced muscle damage. [Subjects and Methods] Thirty healthy, adult male subjects were randomly assigned to the pre-induced muscle damage vibration stimulation group, post-induced muscle damage vibration stimulation group, or control group (n=10 per group). To investigate the effects of pre-induced muscle damage vibration stimulation, changes in the pressure-pain threshold (lb), creatine kinase level (U/L), and lactate dehydrogenase level (U/L) were measured and analyzed at baseline and at 24 hours, 48 hours, and 72 hours after exercise. [Results] The pressure-pain thresholds and concentrations of creatine kinase and lactate dehydrogenase varied significantly in each group and during each measurement period. There were interactions between the measurement periods and groups, and results of the post-hoc test showed that the pre-induced muscle damage vibration stimulation group had the highest efficacy among the groups. [Conclusion] Pre-induced muscle damage vibration stimulation is more effective than post-induced muscle damage vibration stimulation for preventing muscle damage. PMID:28210056

  8. Modeling of fluid-induced vibrations and identification of hydrodynamic forces on flow control valves

    Institute of Scientific and Technical Information of China (English)

    Samad Mehrzad; Ilgar Javanshir; Ahmad Rahbar Ranji; Seyyed Hadi Taheri

    2015-01-01

    Dynamics and vibration of control valves under flow-induced vibration are analyzed. Hydrodynamic load characteristics and structural response under flow-induced vibration are mainly influenced by inertia, damping, elastic, geometric characteristics and hydraulic parameters. The purpose of this work is to investigate the dynamic behavior of control valves in the response to self-excited fluid flow. An analytical and numerical method is developed to simulate the dynamic and vibrational behavior of sliding dam valves, in response to flow excitation. In order to demonstrate the effectiveness of proposed model, the simulation results are validated with experimental ones. Finally, to achieve the optimal valve geometry, numerical results for various shapes of valves are compared. Rounded valve with the least amount of flow turbulence obtains lower fluctuations and vibration amplitude compared with the flat and steep valves. Simulation results demonstrate that with the optimal design requirements of valves, vibration amplitude can be reduced by an average to 30%.

  9. Train-induced field vibration measurements of ground and over-track buildings.

    Science.gov (United States)

    Zou, Chao; Wang, Yimin; Moore, James A; Sanayei, Masoud

    2017-01-01

    Transit-oriented development, such as metro depot and over-track building complexes, has expanded rapidly over the last 5years in China. Over-track building construction has the advantage of comprehensive utilization of land resources, ease of commuting to work, and provide funds for subway construction. But the high frequency of subway operations into and out of the depots can generate excessive vibrations that transmit into the over track buildings, radiate noise within the buildings, hamper the operation of vibration sensitive equipment, and adversely affect the living quality of the building occupants. Field measurements of vibration during subway operations were conducted at Shenzhen, China, a city of 10.62 million people in southern China. Considering the metro depot train testing line and throat area train lines were the main vibration sources, vibration data were captured in five measurement setups. The train-induced vibrations were obtained and compared with limitation of FTA criteria. The structure-radiated noise was calculated using measured vibration levels. The vertical vibration energy directly passed through the columns on both sides of track into the platform, amplifying vibration on the platform by up to 6dB greater than ground levels at testing line area. Vibration amplification around the natural frequency in the vertical direction of over-track building made the peak values of indoor floor vibration about 16dB greater than outdoor platform vibration. We recommend to carefully examining design of new over-track buildings within 40m on the platform over the throat area to avoid excessive vertical vibrations and noise. For both buildings, the measured vertical vibrations were less than the FTA limit. However, it is demonstrated that the traffic-induced high-frequency noise has the potential to annoy occupants on the upper floors.

  10. Low vibration laboratory with a single-stage vibration isolation for microscopy applications

    Science.gov (United States)

    Voigtländer, Bert; Coenen, Peter; Cherepanov, Vasily; Borgens, Peter; Duden, Thomas; Tautz, F. Stefan

    2017-02-01

    The construction and the vibrational performance of a low vibration laboratory for microscopy applications comprising a 100 ton floating foundation supported by passive pneumatic isolators (air springs), which rest themselves on a 200 ton solid base plate, are discussed. The optimization of the air spring system leads to a vibration level on the floating floor below that induced by an acceleration of 10 ng for most frequencies. Additional acoustic and electromagnetic isolation is accomplished by a room-in-room concept.

  11. Payload bay atmospheric vent airflow testing at the Vibration and Acoustic Test Facility

    Science.gov (United States)

    Johnston, James D., Jr.

    1988-01-01

    Several concerns related to venting the Space Shuttle Orbiter payload bay during launch led to laboratory experiments with a flight-type vent box installed in the wall of a subsonic wind tunnel. This report describes the test setups and procedures used to acquire data for characterization of airflow through the vent box and acoustic tones radiated from the vent-box cavity. A flexible boundary-layer spoiler which reduced the vent-tone amplitude is described.

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

    Institute of Scientific and Technical Information of China (English)

    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.

  13. Experiments on reduction of propeller induced interior noise by active control of cylinder vibration

    Science.gov (United States)

    Fuller, C. R.; Jones, J. D.

    1987-01-01

    The feasibility of reducing interior noise caused by advanced turbo propellers by controlling the vibration of aircraft fuselages was investigated by performing experiments in an anechoic chamber with an aircraft model test rig and apparatus. It was found that active vibration control provides reasonable global attenuation of interior noise levels for the cases of resonant (at 576 Hz) and forced (at 708 Hz) system response. The controlling mechanism behind the effect is structural-acoustic coupling between the shell and the contained field, termed interface modal filtering.

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

    Institute of Scientific and Technical Information of China (English)

    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.

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

    Directory of Open Access Journals (Sweden)

    Ailing Yang

    2014-03-01

    Full Text Available 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 increased 7% while the hydraulic efficiency decreased 11.75% as blade outlet angles increased from 18° to 39°. The amplitude of pressure fluctuation at the first blade passing frequency has decreased but increased at the second-order blade passing frequency as the angle growing. The total fluctuation power near volute tongue goes up about 12% every 3° increment of blade outlet angle. The results also show that vibrating-velocity of the volute at second-order blade passing frequency is much higher than at other frequencies, and the velocity increases rapidly as blade outlet angle varies from 18° to 39°. At the same time, the sound pressure level outside the pump has increased about 8.6 dB when the angle increased from 18° to 39°.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  17. Assessment of walking-induced floor vibrations according to the SBR guideline

    NARCIS (Netherlands)

    Lentzen, S.S.K.; Koopman, A.

    2012-01-01

    Lightweight floors are prone to high levels of vibration due to human activities. The Dutch building code imposes regulations on floors with respect to safety, health and serviceability. The walking-induced vibrations of floors are not incorporated in these regulations. The private law arrangement i

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

    NARCIS (Netherlands)

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Langre, E. de [Ecole Polytechnique, Dept. de Mecanique, LadHyX, 91 - Palaiseau (France); Axisa, F. [CEA Saclay 91 - Gif-sur-Yvette (France)

    2004-07-01

    vain. First 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

    Science.gov (United States)

    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. The effects of wood variability on the free vibration of an acoustic guitar top plate.

    Science.gov (United States)

    Shepherd, Micah R; Hambric, Stephen A; Wess, Dennis B

    2014-11-01

    A finite element model of a bare top plate with braces and a bridge plate was created using orthotropic material properties. The natural variation of the wood properties including dependence on moisture content was also determined. The simulated modes were then compared to experimentally obtained modes from top plate prototypes. Uncertainty analysis was also performed to determine the statistical bound of natural variability between wood samples. The natural frequencies of the model fall within the computed error bound. These results reinforce the importance of obtaining accurate material properties for acoustic guitar modeling.

  2. Wind-induced Vibrations in the European Court Towers

    DEFF Research Database (Denmark)

    Hansen, Jannick B.; Brincker, Rune; Andersen, Ken G.;

    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...

  3. Tangential acceleration feedback control of friction induced vibration

    Science.gov (United States)

    Nath, Jyayasi; Chatterjee, S.

    2016-09-01

    Tangential control action is studied on a phenomenological mass-on-belt model exhibiting friction-induced self-excited vibration attributed to the low-velocity drooping characteristics of friction which is also known as Stribeck effect. The friction phenomenon is modelled by the exponential model. Linear stability analysis is carried out near the equilibrium point and local stability boundary is delineated in the plane of control parameters. The system is observed to undergo a Hopf bifurcation as the eigenvalues determined from the linear stability analysis are found to cross the imaginary axis transversally from RHS s-plane to LHS s-plane or vice-versa as one varies the control parameters, namely non-dimensional belt velocity and the control gain. A nonlinear stability analysis by the method of Averaging reveals the subcritical nature of the Hopf bifurcation. Thus, a global stability boundary is constructed so that any choice of control parameters from the globally stable region leads to a stable equilibrium. Numerical simulations in a MATLAB SIMULINK model and bifurcation diagrams obtained in AUTO validate these analytically obtained results. Pole crossover design is implemented to optimize the filter parameters with an independent choice of belt velocity and control gain. The efficacy of this optimization (based on numerical results) in the delicate low velocity region is also enclosed.

  4. Statistical analysis of vibration-induced bone and joint damages.

    Science.gov (United States)

    Schenk, T

    1995-01-01

    Vibration-induced damages to bones and joints are still occupational diseases with insufficient knowledge about causing and moderating factors and resulting damages. For a better understanding of these relationships also retrospective analyses of already acknowledged occupational diseases may be used. Already recorded detailed data for 203 in 1970 to 1979 acknowledged occupational diseases in the building industry and the building material industry of the GDR are the basis for the here described investigations. The data were gathered from the original documents of the occupational diseases and scaled in cooperation of an industrial engineer and an industrial physician. For the purposes of this investigations the data are to distinguish between data which describe the conditions of the work place (e.g. material, tools and posture), the exposure parameters (e.g. beginning of exposure and latency period) and the disease (e.g. anamnestical and radiological data). These data are treated for the use with sophisticated computerized statistical methods. The following analyses were carried out. Investigation of the connections between the several characteristics, which describe the occupational disease (health damages), including the comparison of the severity of the damages at the individual joints. Investigation of the side dependence of the damages. Investigation of the influence of the age at the beginning of the exposure and the age at the acknowledgement of the occupational disease and herewith of the exposure duration. Investigation of the effect of different occupational and exposure conditions.

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

    Science.gov (United States)

    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.

  6. Analysis of Vortex Induced Vibrations of Marine Risers

    Directory of Open Access Journals (Sweden)

    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.

  7. Suppressing molecular vibrations in organic semiconductors by inducing strain.

    Science.gov (United States)

    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

    2016-01-01

    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 cm(2) 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.

  8. Wind-induced vibration experiment on solar wing

    Directory of Open Access Journals (Sweden)

    Tamura Yukio

    2015-01-01

    Full Text Available This paper describes wind tunnel experimental results of wind-induced responses of a solar wing system, and investigates its aeroelastic instability using a scaled model. The model comprised 12 solar wing units, each supported by 2 cables. The gaps between units were set constant. Two sag ratios (i.e. sag/span length were adopted. The wind speed was varied from 0 to 16m/s, and 18 different wind speeds were used. From the experiment, when the sag was 2%, a sudden increase in fluctuating displacement was found near a mean wind speed of 10m/s at a wind direction of 40° A sudden increase in fluctuating displacements was also found near a mean wind speed of 1m/s when the wind direction was larger than 60° When the sag increased to 5%, some differences among units in mean displacements were found and complicate vibration in fluctuating displacement at low wind speed was observed.

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

    Science.gov (United States)

    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.

  10. Experimental Investigation of Wave-Induced Hydroelastic Vibrations of Trimaran in Oblique Irregular Waves

    Directory of Open Access Journals (Sweden)

    Haoyun Tang

    2016-01-01

    Full Text Available The irregular wave condition, especially the oblique irregular wave condition, is the actual circumstances when trimaran is sailing in sea. In order to identify the characteristic of the wave-induced hydroelastic vibration in irregular waves, as well as investigate the change of vibration in different oblique irregular wave conditions, trimaran model tests were conducted to measure vibrations, wave impact, and motion under different azimuth and wave height. The vibration on main hull, side hull, and cross-desk is measured and analyzed separately to observe the influence of irregular wave in different structural parts. The longitudinal vibration, transverse vibration, and torsion are also included in the model tests measurement to investigate the relationship between these vibration deformation components and parameters of the irregular waves. The wave-induced hydroelastic vibrations and whipping effect is extracted and analyzed to find influence of whipping and springing on the total vibration. Based on the analysis, the dangerous positions and the critical waves condition is introduced to ensure that the subsequent structural strength assessment is more reliable.

  11. Fast contactless vibrating structure characterization using real time field programmable gate array-based digital signal processing: demonstrations with a passive wireless acoustic delay line probe and vision.

    Science.gov (United States)

    Goavec-Mérou, G; Chrétien, N; Friedt, J-M; Sandoz, P; Martin, G; Lenczner, M; Ballandras, S

    2014-01-01

    Vibrating mechanical structure characterization is demonstrated using contactless techniques best suited for mobile and rotating equipments. Fast measurement rates are achieved using Field Programmable Gate Array (FPGA) devices as real-time digital signal processors. Two kinds of algorithms are implemented on FPGA and experimentally validated in the case of the vibrating tuning fork. A first application concerns in-plane displacement detection by vision with sampling rates above 10 kHz, thus reaching frequency ranges above the audio range. A second demonstration concerns pulsed-RADAR cooperative target phase detection and is applied to radiofrequency acoustic transducers used as passive wireless strain gauges. In this case, the 250 ksamples/s refresh rate achieved is only limited by the acoustic sensor design but not by the detection bandwidth. These realizations illustrate the efficiency, interest, and potentialities of FPGA-based real-time digital signal processing for the contactless interrogation of passive embedded probes with high refresh rates.

  12. Laser-induced acoustic imaging of underground objects

    Science.gov (United States)

    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.

  13. Acoustic Resonance Frequency Elimination Device for Safety Relief Valves

    Energy Technology Data Exchange (ETDEWEB)

    Redmond, J.

    2014-07-01

    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)

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

    Directory of Open Access Journals (Sweden)

    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.

  15. A Comparative Study of Ground and Underground Vibrations Induced by Bench Blasting

    Directory of Open Access Journals (Sweden)

    Xiuzhi Shi

    2016-01-01

    Full Text Available Ground vibrations originating from bench blasting may cause damage to slopes, structures, and underground workings in close proximity to an operating open-pit mine. It is important to monitor and predict ground vibration levels induced by blasting and to take measures to reduce their hazardous effects. The aims of this paper are to determine the weaker protection objects by comparatively studying bench blasting induced vibrations obtained at surface and in an underground tunnel in an open-pit mine and thus to seek vibration control methods to protect engineering objects at the site. Vibrations arising from measurement devices at surface and in an underground tunnel at the Zijinshan Open-Pit Mine were obtained. Comparative analysis of the peak particle velocities shows that, in the greatest majority of cases, surface values are higher than underground values for the same vibration distance. The transmission laws of surface and underground vibrations were established depending on the type of rock mass, the explosive charge, and the distance. Compared with the Chinese Safety Regulations for Blasting (GB6722-2014, the bench blasting induced vibrations would not currently cause damage to the underground tunnel. According to the maximum allowable peak particle velocities for different objects, the permitted maximum charges per delay are obtained to reduce damage to these objects at different distances.

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

    Directory of Open Access Journals (Sweden)

    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.

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

    Institute of Scientific and Technical Information of China (English)

    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.

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

    Directory of Open Access Journals (Sweden)

    Yiwen Zheng

    2014-01-01

    Full Text Available 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.

  19. Numerical simulation of corona-induced vibration of high voltage conductor

    Institute of Scientific and Technical Information of China (English)

    A. GOURBI; M. BRAHAMI; A. TILMATINE; P. PIROTTE

    2009-01-01

    When it rains, electric power transmission lines start vibrating due to corona effect. This type of vibration is known as "corona-induced vibration". The aim of this paper is to elaborate a mathematical model for numerical simulation of the corona-induced vibration, with consid-eration of the influence of the magnitude and the polarity of the electric field on the conductor surface. Finite element method was employed to develop the numerical model,and the finite difference method was used for the time discretisation. The moment of application of the corona-induced force is evaluated using the resultant vertical force applied to a water drop, suspended under a high voltage conductor. Some experimental results of other authors are exploited to evaluate the precision of the simulation and the validation of numerical results.

  20. Vibration induced sliding: theory and experiment for a beam with a spring-loaded mass

    DEFF Research Database (Denmark)

    Miranda, Erik; Thomsen, Jon Juel

    1998-01-01

    The study sets up a simple model for predicting vibration induced sliding of mass, and provides quantitative experimental evidence for the validity of the model. The results lend confidence to recent theoretical developments on using vibration induced sliding for passive vibration damping......, and contributes to a further understanding of this nonlinear phenomenon. A mathematical model is set up to describe vibration induced sliding for a base-excited cantilever beam with a spring-loaded pointmass. Approximations simplify the model into two nonlinear ordinary differential equations, describing motions...... of the system at near-resonant excitation of a single beam mode. This simplified model is studied numerically and analytically, and tested against laboratory experiments. The experiments provide evidence that the simplified mathematical model retains those features of the real system that are necessary...

  1. Analytical and experimental studies of flow-induced vibration of SSME components

    Science.gov (United States)

    Chen, S. S.; Jendrzejczyk, J. A.; Wambsganss, M. W.

    1987-01-01

    Components of the Space Shuttle Main Engines (SSMEs) are subjected to a severe environment that includes high-temperature, high-velocity flows. Such flows represent a source of energy that can induce and sustain large-amplitude vibratory stresses and/or result in fluidelastic instabilities. Three components are already known to have experienced failures in evaluation tests as a result of flow-induced structural motion. These components include the liquid-oxygen (LOX) posts, the fuel turbine bellows shield, and the internal inlet tee splitter vane. Researchers considered the dynamic behavior of each of these components with varying degrees of effort: (1) a theoretical and experimental study of LOX post vibration excited by a fluid flow; (2) an assessment of the internal inlet tee splitter vane vibration (referred to as the 4000-Hz vibration problem); and (3) a preliminary consideration of the bellows shield problem. Efforts to resolve flow-induced vibration problems associated with the SSMEs are summarized.

  2. Numerical study of friction-induced instability and acoustic radiation - Effect of ramp loading on the squeal propensity for a simplified brake model

    Science.gov (United States)

    Soobbarayen, K.; Sinou, J.-J.; Besset, S.

    2014-10-01

    This paper presents a numerical study of the influence of loading conditions on the vibrational and acoustic responses of a disc brake system subjected to squeal. A simplified model composed of a circular disc and a pad is proposed. Nonlinear effects of contact and friction over the frictional interface are modelled with a cubic law and a classical Coulomb's law with a constant friction coefficient. The stability analysis of this system shows the presence of two instabilities with one and two unstable modes that lead to friction-induced nonlinear vibrations and squeal noise. Nonlinear time analysis by temporal integration is conducted for two cases of loadings and initial conditions: a static load near the associated sliding equilibrium and a slow and a fast ramp loading. The analysis of the time responses shows that a sufficiently fast ramp loading can destabilize a stable configuration and generate nonlinear vibrations. Moreover, the fast ramp loading applied for the two unstable cases generates higher amplitudes of velocity than for the static load cases. The frequency analysis shows that the fast ramp loading generates a more complex spectrum than for the static load with the appearance of new resonance peaks. The acoustic responses for these cases are estimated by applying the multi-frequency acoustic calculation method based on the Fourier series decomposition of the velocity and the Boundary Element Method. Squeal noise emissions for the fast ramp loading present lower or higher levels than for the static load due to the different amplitudes of velocities. Moreover, the directivity is more complex for the fast ramp loading due to the appearance of new harmonic components in the velocity spectrum. Finally, the sound pressure convergence study shows that only the first harmonic components are sufficient to well describe the acoustic response.

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

    Indian Academy of Sciences (India)

    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.

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

    Directory of Open Access Journals (Sweden)

    Benoit eDelhaye

    2012-07-01

    Full Text Available Humans can detect and discriminate between fine variations of surface roughness using activetouch. It is hitherto believed that roughness perception is mediated mostly by cutaneous andsubcutaneous afferents located in the fingertips. However, recent findings have shown thatfollowing abolishment of cutaneous afferences resulting from trauma or pharmacologicalintervention, the ability of subjects to discriminate between textures roughness was notsignificantly altered. These findings suggest that the somatosensory system is able to collecttextural information from other sources than fingertip afference. It follows that signalsresulting of the interaction of a finger with a rough surface must be transmitted to stimulatereceptor populations in regions far away from the contact. This transmission was characterizedby measuring in the wrist vibrations originating at the fingertip and thus propagating throughthe finger, the hand and the wrist during active exploration of textured surfaces. The spectralanalysis of the vibrations taking place in the forearm tissues revealed regularities that werecorrelated with the scanned surface and the speed of exploration. In the case of periodictextures, the vibration signal contained a fundamental frequency component corresponding tothe finger velocity divided by the spatial period of the stimulus. This regularity was found for awide range of textural length scales and scanning velocities. For non-periodic textures, thespectrum of the vibration did not contain obvious features that would enable discriminationbetween the different stimuli. However, for both periodic and non-periodic stimuli, theintensity of the vibrations could be related to the microgeometry of the scanned surfaces.

  5. Evaluation of annealing and double ion beam irradiation by a laser-induced and laser-detected surface acoustic wave diagnostic system

    Science.gov (United States)

    Kitazawa, Sin-iti; Wakai, Eiichi; Aoto, Kazumi

    2016-10-01

    The effects of annealing and double ion irradiation on nuclear structural materials were investigated using a novel, non-destructive, non-contact diagnostic method. A laser-induced and laser-detected surface acoustic wave (SAW) was adopted as a diagnostic system. The SAWs propagation velocity and the SAWs vibration velocity along the normal direction of the surface were measured to investigate mechanical properties of the substrates. Change of the shear modulus was detected in the annealed substrates. Non-linear effect on amplitude of the excited SAW was observed on the double ion irradiated materials. The potential of the SAW diagnostic system for assessing nuclear structural materials was demonstrated.

  6. Heart rate responses induced by acoustic tempo and its interaction with basal heart rate

    Science.gov (United States)

    Watanabe, Ken; Ooishi, Yuuki; Kashino, Makio

    2017-01-01

    Many studies have revealed the influences of music on the autonomic nervous system (ANS). Since previous studies focused on the effects of acoustic tempo on the ANS, and humans have their own physiological oscillations such as the heart rate (HR), the effects of acoustic tempo might depend on the HR. Here we show the relationship between HR elevation induced by acoustic tempo and individual basal HR. Since high tempo-induced HR elevation requires fast respiration, which is based on sympatho-respiratory coupling, we controlled the participants’ respiration at a faster rate (20 CPM) than usual (15 CPM). We found that sound stimuli with a faster tempo than the individual basal HR increased the HR. However, the HR increased following a gradual increase in the acoustic tempo only when the extent of the gradual increase in tempo was within a specific range (around + 2%/min). The HR did not follow the increase in acoustic tempo when the rate of the increase in the acoustic tempo exceeded 3% per minute. These results suggest that the effect of the sympatho-respiratory coupling underlying the HR elevation caused by a high acoustic tempo depends on the basal HR, and the strength and the temporal dynamics of the tempo. PMID:28266647

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

    Science.gov (United States)

    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 v(1)≪c(s) for the validity of the perturbation expansion is replaced by the more restrictive criterion v(1)≪c(s)/Q. Our numerical model is available as supplemental material in the form of comsol model files and matlab scripts.

  8. Droplets Acoustics

    CERN Document Server

    Dahan, Raphael; Carmon, Tal

    2015-01-01

    Contrary to their capillary resonances (Rayleigh, 1879) and their optical resonances (Ashkin, 1977), droplets acoustical resonances were rarely considered. Here we experimentally excite, for the first time, the acoustical resonances of a droplet that relies on sound instead of capillary waves. Droplets vibrations at 37 MHz rates and 100 quality factor are optically excited and interrogated at an optical threshold of 68 microWatt. Our vibrations span a spectral band that is 1000 times higher when compared with drops previously-studied capillary vibration.

  9. Field measurements and analyses of environmental vibrations induced by high-speed Maglev.

    Science.gov (United States)

    Li, Guo-Qiang; Wang, Zhi-Lu; Chen, Suwen; Xu, You-Lin

    2016-10-15

    Maglev, offers competitive journey-times compared to the railway and subway systems in markets for which distance between the stations is 100-1600km owing to its high acceleration and speed; however, such systems may have excessive vibration. Field measurements of Maglev train-induced vibrations were therefore performed on the world's first commercial Maglev line in Shanghai, China. Seven test sections along the line were selected according to the operating conditions, covering speeds from 150 to 430km/h. Acceleration responses of bridge pier and nearby ground were measured in three directions and analyzed in both the time and frequency domain. The effects of Maglev train speed on vibrations of the bridge pier and ground were studied in terms of their peak accelerations. Attenuation of ground vibration was investigated up to 30m from the track centerline. Effects of guideway configuration were also analyzed based on the measurements through two different test sections with same train speed of 300km/h. The results showed that peak accelerations exhibited a strong correlation with both train speed and distance off the track. Guideway configuration had a significant effect on transverse vibration, but a weak impact on vertical and longitudinal vibrations of both bridge pier and ground. Statistics indicated that, contrary to the commonly accepted theory and experience, vertical vibration is not always dominant: transverse and longitudinal vibrations should also be considered, particularly near turns in the track. Moreover, measurements of ground vibration induced by traditional high-speed railway train were carried out with the same testing devices in Bengbu in the Anhui Province. Results showed that the Maglev train generates significantly different vibration signatures as compared to the traditional high-speed train. The results obtained from this paper can provide good insights on the impact of Maglev system on the urban environment and the quality of human life

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

    Institute of Scientific and Technical Information of China (English)

    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.

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

    Directory of Open Access Journals (Sweden)

    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

    Science.gov (United States)

    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. Experimental study of shell side flow-induced vibration of conical spiral tube bundle

    Institute of Scientific and Technical Information of China (English)

    闫柯; 葛培琪; 洪军

    2013-01-01

    Conical spiral tube bundles are widely used in enhancing the heat transfer via the flow-induced vibration in heat exchangers. The shell side flow-induced vibration of the conical spiral tube bundle is experimentally investigated in this paper. The experiment table was built and the operational modes, the vibration parameters of the tube bundle were analyzed. The results show that, the operational mode frequencies of the conical spiral tube are decreased as the shell-side fluid flow velocity increases, especially for the first order frequency. Within the parameter range of this experiment, the real working frequency of the conical spiral tube is between the 1st and the 2nd operational modes, and the free end vibration amplitude of the tube bundle increases greatly when the shell side fluid flow velocity exceeds a critical value.

  14. Software Practicalization for Analysis of Wind-Induced Vibrations of Large Span Roof Structures

    Institute of Scientific and Technical Information of China (English)

    ZHANG Enuo; YANG Weiguo; ZHEN Wei; NA Xiangqian

    2005-01-01

    Wind loads are key considerations in the structural design of large-span structures since wind loads can be more important than earthquake loads, especially for large flexible structures. The analysis of wind loads on large span roof structures (LSRS) requires large amounts of calculations. Due to the combined effects of horizontal and vertical winds, the wind-induced vibrations of LSRS are analyzed in this paper with the frequency domain method as the first application of method for the analysis of the wind response of LSRS. A program is developed to analyze the wind-induced vibrations due to a combination of wind vibration modes. The program, which predicts the wind vibration coefficient and the wind pressure acting on the LSRS, interfaces with other finite element software to facilitate analysis of wind loads in the design of LSRS. The effectiveness and accuracy of the frequency domain method have been verified by numerical analyses of practical projects.

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

    CERN Document Server

    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...

  16. Acoustically enhanced heat transport

    Energy Technology Data Exchange (ETDEWEB)

    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. Acoustically enhanced heat transport

    Science.gov (United States)

    Ang, Kar M.; Yeo, Leslie Y.; Friend, James R.; Hung, Yew Mun; Tan, Ming K.

    2016-01-01

    We investigate the enhancement of heat transfer in the nucleate boiling regime by inducing high frequency acoustic waves (f ˜ 106 Hz) on the heated surface. In the experiments, liquid droplets (deionized water) are dispensed directly onto a heated, vibrating substrate. At lower vibration amplitudes (ξs ˜ 10-9 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 (ξs ˜ 10-8 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 10-8 m with 106 Hz order frequencies is observed to produce an improvement of up to 50% reduction in the surface temperature over the case without acoustic excitation.

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

    Institute of Scientific and Technical Information of China (English)

    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.

  19. Train-induced ground vibrations: modeling and experiments

    NARCIS (Netherlands)

    Ditzel, A.

    2003-01-01

    Ground vibrations generated by high-speed trains are of great concern because of the possible damage they can cause to buildings or other structures near the track, and the annoyance to the public living in the vicinity of the track. Particularly in soft-soil regions, where the wave speed is compara

  20. A direct pedestrian-structure interaction model to characterize the human induced vibrations on slender footbridges

    OpenAIRE

    Jiménez-Alonso, J. F.; Sáez, A.

    2014-01-01

    Although the scientific community had knowledge of the human induced vibration problems in structures since the end of the 19th century, it was not until the occurrence of the vibration phenomenon happened in the Millennium Bridge (London, 2000) that the importance of the problem revealed and a higher level of attention devoted. Despite the large advances achieved in the determination of the human-structure interaction force, one of the main deficiencies of the existing models is the exclusio...

  1. 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

    Science.gov (United States)

    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.

  2. Running train induced vibrations and noises of elevated railway structures and their influences on environment

    Institute of Scientific and Technical Information of China (English)

    He XIA; Fei GAO; Xuan WU; Nan ZHANG; Guido DE ROECK; Geert DEGRANDE

    2009-01-01

    The vibrations and noises of elevated railway structures have been cause for concern due to their effects on the environment and the people living near elevated lines. In this paper, the main structural features of some new elevated bridges and station hall were introduced. The generation mechanism of vibrations and noise of elevated structures induced by trains were investigated. The noise induced by different types of elevated bridges, their influences on the environment and the theoretical method for the analysis of structure borne noise was analyzed.Finally, several field measurements on train induced noises at the platforms of elevated subway stations and bridges were presented.

  3. Laboratory for Structural Acoustics

    Data.gov (United States)

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

  4. Shallow Water Acoustic Laboratory

    Data.gov (United States)

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

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

    Science.gov (United States)

    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

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

    DEFF Research Database (Denmark)

    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...

  7. 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

    OpenAIRE

    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.

  8. Experimental study of acoustic damping induced by gas-liquid scheme injectors in a combustion chamber

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hak Soon; Sohn, Chae Hoon [Chosun University, Gwangju (Korea, Republic of)

    2007-01-15

    In a liquid rocket engine, acoustic damping induced by gas-liquid scheme injectors is studied experimentally for combustion stability by adopting linear acoustic test. In the previous work, it has been found that gas-liquid scheme injector can play a significant role in acoustic damping or absorption when it is tuned finely. Based on this finding, acoustic-damping characteristics of multi-injectors are intensively investigated. From the experimental data, it is found that acoustic oscillations are almost damped out by multi-injectors when they have the tuning length proposed in the previous study. The length corresponds to a half wavelength of the first longitudinal overtone mode traveling inside the injector with the acoustic frequency intended for damping in the chamber. But, new injector-coupled acoustic modes show up in the chamber with the injectors of the tuning length although the target mode is nearly damped out. And, appreciable frequency shift is always observed except for the case of the worst tuned injector. Accordingly, it is proposed that the tuning length is adjusted to have the shorter length than a half wavelength when these phenomena are considered

  9. Energy harvesting by means of flow-induced vibrations on aerospace vehicles

    Science.gov (United States)

    Li, Daochun; Wu, Yining; Da Ronch, Andrea; Xiang, Jinwu

    2016-10-01

    This paper reviews the design, implementation, and demonstration of energy harvesting devices that exploit flow-induced vibrations as the main source of energy. Starting with a presentation of various concepts of energy harvesters that are designed to benefit from a general class of flow-induced vibrations, specific attention is then given at those technologies that may offer, today or in the near future, a potential benefit to extend the operational capabilities and to monitor critical parameters of unmanned aerial vehicles. Various phenomena characterized by flow-induced vibrations are discussed, including limit cycle oscillations of plates and wing sections, vortex-induced and galloping oscillations of bluff bodies, vortex-induced vibrations of downstream structures, and atmospheric turbulence and gusts. It was found that linear or linearized modeling approaches are commonly employed to support the design phase of energy harvesters. As a result, highly nonlinear and coupled phenomena that characterize flow-induced vibrations are neglected in the design process. The Authors encourage a shift in the current design paradigm: considering coupled nonlinear phenomena, and adequate modeling tools to support their analysis, from a design limitation to a design opportunity. Special emphasis is placed on identifying designs and implementations applicable to aircraft configurations. Application fields of flow-induced vibrations-based energy harvesters are discussed including power supply for wireless sensor networks and simultaneous energy harvest and control. A large body of work on energy harvesters is included in this review journal. Whereas most of the references claim direct applications to unmanned aerial vehicles, it is apparent that, in most of the cases presented, the working principles and characteristics of the energy harvesters are incompatible with any aerospace applications. Finally, the challenges that hold back the integration of energy harvesting

  10. Vertical random vibration analysis of adjacent building induced by highway traffic load

    Directory of Open Access Journals (Sweden)

    Wentao Xu

    2016-08-01

    Full Text Available Vehicle–pavement coupling systems may produce strong vertical random vibration due to the road surface unevenness and then further induce random vibration of adjacent buildings. It is usually difficult to numerical analyze efficiently as the model precision and calculation scale of complicated random analysis. In this article, a longitudinal infinite Kirchhoff plate with Kelvin foundation is employed to model the pavement system, and by proving the symplectic orthogonal characteristic for the damped chain substructure, the infinitely long road surface is regarded as a periodic chain-type substructure, the model is accurate, and computation scale is reduced. Models of a half vehicle and an adjacent building are coupled to the plate to produce a unified finite element model. The plate element stiffness matrix is formulated in the coordinate moving with the load, a typical model of road substructure is built, and the two-dimensional moving element method of vertical coupling random vibration is formulated, and then the time-varying non-stationary random vibration may be transformed into time-invariant stationary system. Using the pseudo-excitation method, vertical dynamic responses of the unified model of vibration source, supporting structure, and vibrated structure are analyzed. The computation efficiency of this method is numerically justified and some vibration influence rules of vehicle to building are drawn.

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

    Institute of Scientific and Technical Information of China (English)

    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.

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

    Institute of Scientific and Technical Information of China (English)

    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.

  13. Investigation into piston-slap-induced vibration for engine condition simulation and monitoring

    Science.gov (United States)

    Geng, Z.; Chen, J.

    2005-04-01

    Piston slap is a common impact phenomenon existing in the reciprocating engine. It is also a major cause of the complex transient vibration response related to the impact excitation inside the engine. In order to correlate the piston-slap impact with the slap-induced vibration and consequently find out an effective approach for the engine dynamic behaviour simulation and working condition monitoring, an in-depth investigation from theoretical modelling to experimental verification is made in this paper. Firstly, the piston-slap phenomenon inside the reciprocating engine is briefly discussed from the viewpoint of engine mechanics. Based upon this, a nonlinear model is developed to simulate the slap-induced vibration response. Using numerical integration procedure, the slap-induced vibration response and its correlation with the inner-cylinder piston-slap impact are reasonably evaluated. Guided by the simulating results and, by introducing a fast wavelet-packet decomposition and reconstruction algorithm, a specially designed experiment is made to practically measure and extract the slap-induced impact message inside the 6190Z LC diesel engine. Comparison between the simulation and practically measured and reconstructed engine vibration signals verifies the effectiveness and practicality of this approach for more detailed academic research and engineering application.

  14. Excitation of Light-Induced Acoustic Waves in Doped Lithium Niobate Crystals

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The phenomena of acoustic emission in doped lithium niobate crystals were observed in the process of light-induced quasi-breakdown. It is found that the ultrasonic waves introduce into the crystal have been modulated by the low frequency acoustic waves. Its frequency increases with the rise of the intensity of incident light and its jump period of breakdown is the same as that of the photovoltaic current Ic, the change of light-induced refractive index Δn and the diffracted light intensity L. This effect was explained with the interaction of the three waves and resonant state theory. The experimental results and the theoretical analysis are in conformity.

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

    Directory of Open Access Journals (Sweden)

    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.

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

    Science.gov (United States)

    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.

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

    CERN Document Server

    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...

  18. Experimental investigation of the flow-induced vibration of hydrofoils in cavitating flows

    Science.gov (United States)

    Wang, Guoyu; Wu, Qin; Huang, Biao; Gao, Yuan

    2015-12-01

    The objective of this paper is to investigate the correlation between fluid induced vibration and unsteady cavitation behaviours. Experimental results are presented for a modified NACA66 hydrofoil, which is fixed at α=8°. The high-speed camera is synchronized with a single point Laser Doppler Vibrometer to analyze the transient cavitating flow structures and the corresponding structural vibration characteristics. The results showed that, with the decreasing of the cavitation number, the cavitating flows in a water tunnel display several types of cavitation patterns, such as incipient cavitation, sheet cavitation and cloud cavitation. The cavity shedding frequency reduces with the decrease of the cavitation number. As for the cloud cavitation regime, the trend of the vibration velocity goes up with the growth of the attached cavity, accompanied with small amplitude fluctuations. Then the collapse and shedding of the large-scale cloud cavities leads to substantial increase of the vibration velocity fluctuations.

  19. Experimental study and numerical simulation on vortex-induced vibration of flexible riser

    Institute of Scientific and Technical Information of China (English)

    LOU Min; QUO Haiyan; DONG Wenyi

    2007-01-01

    In order to study the effect of internal flow on vortex-induced vibration of flexible riser, the experiment on the vortex - induced vibration of flexible riser transporting fluid in the current was conducted in the physical oceanography laboratory of Ocean University of China. Considering the internal flowing fluid and external marine environment, the dynamic response of the flexible riser was measured. The corresponding numerical simulation was performed using the wake oscillatory model considering the extensibility of the riser system. Both the experiment and the numerical simulation indicated that with the increase of internal flow speed, the response amplitude increases, while the response frequency decreases.

  20. Measurement of ground and nearby building vibration and noise induced by trains in a metro depot.

    Science.gov (United States)

    Zou, Chao; Wang, Yimin; Wang, Peng; Guo, Jixing

    2015-12-01

    Metro depots are where subway trains are parked and where maintenance is carried out. They usually occupy the largest ground areas in metro projects. Due to land utilization problems, Chinese cities have begun to develop over-track buildings above metro depots for people's life and work. The frequently moving trains, when going into and out of metro depots, can cause excessive vibration and noise to over-track buildings and adversely affect the living quality of the building occupants. Considering the current need of reliable experimental data for the construction of metro depots, field measurements of vibration and noise on the ground and inside a nearby 3-story building subjected to moving subway trains were conducted in a metro depot at Guangzhou, China. The amplitudes and frequency contents of velocity levels were quantified and compared. The composite A-weighted equivalent sound levels and maximum sound levels were captured. The predicted models for vibration and noise of metro depot were proposed based on existing models and verified. It was found that the vertical vibrations were significantly greater than the horizontal vibrations on the ground and inside the building near the testing line. While at the throat area, the horizontal vibrations near the curved track were remarkably greater than the vertical vibrations. The attenuation of the vibrations with frequencies above 50 Hz was larger than the ones below 50 Hz, and the frequencies of vibration transmitting to adjacent buildings were mainly within 10-50 Hz. The largest equivalent sound level generated in the throat area was smaller than the testing line one, but the instantaneous maximum sound level induced by wheels squeal, contact between wheels and rail joints as well as turnout was close to or even greater than the testing line one. The predicted models gave a first estimation for design and assessment of newly built metro depots.

  1. Vibration-induced field fluctuations in a superconducting magnet

    Science.gov (United States)

    Britton, J. W.; Bohnet, J. G.; Sawyer, B. C.; Uys, H.; Biercuk, M. J.; Bollinger, J. J.

    2016-06-01

    Superconducting magnets enable precise control of nuclear and electron spins, and are used in experiments that explore biological and condensed-matter systems, and fundamental atomic particles. In high-precision applications, a common view is that slow (Be+9 electron-spin qubits in the 4.46 -T field of a superconducting magnet. We measure a spin-echo T2 coherence time of ˜6 ms for the Be+9 electron-spin resonance at 124 GHz , limited by part-per-billion fractional fluctuations in the magnet's homogeneous field. Vibration isolation of the magnet improved T2 to ˜50 ms.

  2. Loss-induced Enhanced Transmission in Anisotropic Density-near-zero Acoustic Metamaterials

    Science.gov (United States)

    Shen, Chen; Jing, Yun

    2016-11-01

    Anisotropic density-near-zero (ADNZ) acoustic metamaterials are investigated theoretically and numerically in this paper and are shown to exhibit extraordinary transmission enhancement when material loss is induced. The enhanced transmission is due to the enhanced propagating and evanescent wave modes inside the ADNZ medium thanks to the interplay of near-zero density, material loss, and high wave impedance matching in the propagation direction. The equi-frequency contour (EFC) is used to reveal whether the propagating wave mode is allowed in ADNZ metamaterials. Numerical simulations based on plate-type acoustic metamaterials with different material losses were performed to demonstrate collimation and subwavelength imaging enabled by the induced loss in ADNZ media. This work provides a different way for manipulating acoustic waves.

  3. Loss-induced enhanced transmission in anisotropic density-near-zero acoustic metamaterials

    CERN Document Server

    Shen, Chen

    2016-01-01

    Anisotropic density-near-zero (ADNZ) acoustic metamaterials are investigated theoretically and numerically in this letter and are shown to exhibit extraordinary transmission enhancement when material loss is induced. The enhanced transmission is due to the enhanced propagating and evanescent wave modes inside the ADNZ medium thanks to the interplay of near-zero density, material loss, and high wave impedance matching in the propagation direction. The equi-frequency contour (EFC) is used to reveal whether the propagating wave mode is allowed in ADNZ metamaterials. Numerical simulations based on plate-type acoustic metamaterials with different material losses were performed to demonstrate collimation enabled by the induced loss in ADNZ media. This work provides a different way for manipulating acoustic waves.

  4. Light-induced acoustic effect in LiNbO3:Fe:Ce crystals

    Institute of Scientific and Technical Information of China (English)

    Huang Wei; Wu Zhong-Kang; Wang Chang-Qing

    2005-01-01

    The phenomena of acoustic emission in LiNbO3:Fe:Ce crystals have been observed in the process of light-induced quasi-breakdown. It is found that the ultra-high frequency acoustic signal introduced into the crystal is modulated by the low frequency acoustic waves. Its frequency increases with the increase of the intensity of incident light and its jump period of breakdown is the same as that of the photovoltaic current Ic, the change of light-induced refractive index △n and the diffracted light intensity L. This phenomenon has been analysed in this paper, which is caused by the inverse piezoelectric strain effect of the jump of space charge field during the quasi-breakdown.

  5. Building vibrations induced by noise from rotorcraft and propeller aircraft flyovers

    Science.gov (United States)

    Shepherd, Kevin P.; Hubbard, Harvey H.

    1992-01-01

    Noise and building vibrations were measured for a series of helicopter and propeller-driven aircraft flyovers at WFF during May 1978. The building response data are compared with similar data acquired earlier at sites near Dulles and Kennedy Airports for operation of commercial jet transports, including the Concorde supersonic transport. Results show that noise-induced vibration levels in windows and walls are directly proportional to sound pressure level and that for a given noise level, the acceleration levels induced by a helicopter or a propeller-driven aircraft flyover cannot be distinguished from the acceleration levels induced by a commercial jet transport flyover. Noise-induced building acceleration levels were found to be lower than those levels which might be expected to cause structural damage and were also lower than some acceleration levels induced by such common domestic events as closing windows and doors.

  6. Vibration serviceability of footbridges under human-induced excitation: a literature review

    Science.gov (United States)

    Živanović, S.; Pavic, A.; Reynolds, P.

    2005-01-01

    Increasing strength of new structural materials and longer spans of new footbridges, accompanied with aesthetic requirements for greater slenderness, are resulting in more lively footbridge structures. In the past few years this issue attracted great public attention. The excessive lateral sway motion caused by crowd walking across the infamous Millennium Bridge in London is the prime example of the vibration serviceability problem of footbridges. In principle, consideration of footbridge vibration serviceability requires a characterisation of the vibration source, path and receiver. This paper is the most comprehensive review published to date of about 200 references which deal with these three key issues. The literature survey identified humans as the most important source of vibration for footbridges. However, modelling of the crowd-induced dynamic force is not clearly defined yet, despite some serious attempts to tackle this issue in the last few years. The vibration path is the mass, damping and stiffness of the footbridge. Of these, damping is the most uncertain but extremely important parameter as the resonant behaviour tends to govern vibration serviceability of footbridges. A typical receiver of footbridge vibrations is a pedestrian who is quite often the source of vibrations as well. Many scales for rating the human perception of vibrations have been found in the published literature. However, few are applicable to footbridges because a receiver is not stationary but is actually moving across the vibrating structure. During footbridge vibration, especially under crowd load, it seems that some form of human-structure interaction occurs. The problem of influence of walking people on footbridge vibration properties, such as the natural frequency and damping is not well understood, let alone quantified. Finally, there is not a single national or international design guidance which covers all aspects of the problem comprehensively and some form of their

  7. An Experimental Investigation of Vibration-Induced Droplet Atomization.

    Science.gov (United States)

    Vukasinovic, Bojan; Smith, Marc K.; Glezer, Ari

    1998-11-01

    The atomization process in a mm-scale liquid droplet placed on a vibrating membrane is investigated experimentally. When the wavelength of the Faraday surface waves is smaller than the characteristic dimension of the droplet, the waves grow in amplitude as the excitation amplitude increases and ultimately begin to eject small secondary droplets from the wave crests. The high membrane acceleration needed to attain ejection (typically 300g) is achieved by driving a light-weight membrane near its resonant frequencies (nominally 1000-6000 Hz). The evolution and rate of the droplet-ejection process depend on a coupled system dynamic between the liquid droplet and the vibrating membrane. Depending on the excitation frequency and amplitude, various types of droplet-ejection processes can occur. For example, when step forcing (with prescribed frequency and amplitude) is applied, rapid atomization occurs. This event is triggered along the circumference of the droplet near the contact line by a strong azimuthal instability. In the present experiments, the droplet-ejection process and the resulting spray characteristics are investigated using high-speed video and two-frame particle tracking velocimetry.

  8. Dissociative ionization of liquid water induced by vibrational overtone excitation

    Energy Technology Data Exchange (ETDEWEB)

    Natzle, W.C.

    1983-03-01

    Photochemistry of vibrationally activated ground electronic state liquid water to produce H/sup +/ and OH/sup -/ ions has been initiated by pulsed, single-photon excitation of overtone and combination transitions. Transient conductivity measurements were used to determine quantum yields as a function of photon energy, isotopic composition, and temperature. The equilibrium relaxation rate following perturbation by the vibrationally activated reaction was also measured as a function of temperature reaction and isotopic composition. In H/sub 2/O, the quantum yield at 283 +- 1 K varies from 2 x 10/sup -9/ to 4 x 10/sup -5/ for wave numbers between 7605 and 18140 cm/sup -1/. In D/sub 2/O, the dependence of quantum yield on wavelength has the same qualitative shape as for H/sub 2/O, but is shifted to lower quantum yields. The position of a minimum in the quantum yield versus hydrogen mole fraction curve is consistent with a lower quantum yield for excitation of HOD in D/sub 2/O than for excitation of D/sub 2/O. The ionic recombination distance of 5.8 +- 0.5 A is constant within experimental error with temperature in H/sub 2/O and with isotopic composition at 25 +- 1/sup 0/C.

  9. Application of coupled analysis methods for prediction of blast-induced dominant vibration frequency

    Science.gov (United States)

    Li, Haibo; Li, Xiaofeng; Li, Jianchun; Xia, Xiang; Wang, Xiaowei

    2016-03-01

    Blast-induced dominant vibration frequency (DVF) involves a complex, nonlinear and small sample system considering rock properties, blasting parameters and topography. In this study, a combination of grey relational analysis and dimensional analysis procedures for prediction of dominant vibration frequency are presented. Six factors are selected from extensive effect factor sequences based on grey relational analysis, and then a novel blast-induced dominant vibration frequency prediction is obtained by dimensional analysis. In addition, the prediction is simplified by sensitivity analysis with 195 experimental blast records. Validation is carried out for the proposed formula based on the site test database of the firstperiod blasting excavation in the Guangdong Lufeng Nuclear Power Plant (GLNPP). The results show the proposed approach has a higher fitting degree and smaller mean error when compared with traditional predictions.

  10. Vacuum-Induced Coherence in Ultracold Photoassociative Ro-Vibrational Excitations

    CERN Document Server

    Das, Sumanta; Deb, Bimalendu

    2011-01-01

    We show that coherence between two excited ro-vibrational states belonging to the same molecular electronic configuration arises quite naturally due to their interaction with electromagnetic vacuum. For initial preparation of a molecule in the desired ro-vibrational states, we propose to employ the method of ultracold photoassociation. Spontaneous decay of the excited molecule then gives rise to vacuum induced coherence between the excited ro-vibrational states. We demonstrate theoretically an interesting interplay of effects due to vacuum induced coherence and photoassociation. We apply our theory to photoassociation of bosonic Ytterbium (^{174}Yb) atoms which appear to be a promising system for exploring such interplay. The effects discussed here can be important for controlling decoherence and dissipation in molecular systems.

  11. Reducing friction-induced vibration using intelligent active force control (AFC) with piezoelectric actuators

    Indian Academy of Sciences (India)

    S M Hashemi-Dehkordi; A R Abu-Bakar; M Mailah

    2012-12-01

    In this paper, a novel approach to reduce the effect of mode coupling that causes friction induced vibration (FIV) is proposed by applying an intelligent active force control (AFC)-based strategy employing piezoelectric actuators with hysteresis effect to a simplified two degree-of-freedom mathematical model of a friction-induced vibration system. At first, the model is simulated and analysed using a closed loop pure Proportional-Integral-Derivative (PID) controller. Later, it is integrated with the intelligent AFC with fuzzy logic (FL) estimator and simulated under similar operating condition. After running several tests with different sets of operating and loading conditions, the results both in time and frequency domains show that the PID controller with the intelligent AFC is much more effective in reducing the vibration, compared to the pure PID controller alone.

  12. Oscillating load-induced acoustic emission in laboratory experiment

    Science.gov (United States)

    Ponomarev, Alexander; Lockner, David A.; Stroganova, S.; Stanchits, S.; Smirnov, V.

    2010-01-01

    Spatial and temporal patterns of acoustic emission (AE) were studied. A pre-fractured cylinder of granite was loaded in a triaxial machine at 160 MPa confining pressure until stick-slip events occurred. The experiments were conducted at a constant strain rate of 10−7 s−1 that was modulated by small-amplitude sinusoidal oscillations with periods of 175 and 570 seconds. Amplitude of the oscillations was a few percent of the total load and was intended to simulate periodic loading observed in nature (e.g., earth tides or other sources). An ultrasonic acquisition system with 13 piezosensors recorded acoustic emissions that were generated during deformation of the sample. We observed a correlation between AE response and sinusoidal loading. The effect was more pronounced for higher frequency of the modulating force. A time-space spectral analysis for a “point” process was used to investigate details of the periodic AE components. The main result of the study was the correlation of oscillations of acoustic activity synchronized with the applied oscillating load. The intensity of the correlated AE activity was most pronounced in the “aftershock” sequences that followed large-amplitude AE events. We suggest that this is due to the higher strain-sensitivity of the failure area when the sample is in a transient, unstable mode. We also found that the synchronization of AE activity with the oscillating external load nearly disappeared in the period immediately after the stick-slip events and gradually recovered with further loading.

  13. A distributed fiber vibration sensor utilizing dispersion induced walk-off effect in a unidirectional Mach-Zehnder interferometer.

    Science.gov (United States)

    Chen, Qingming; Jin, Chao; Bao, Yuan; Li, Zhaohui; Li, Jianping; Lu, Chao; Yang, Liang; Li, Guifang

    2014-02-10

    We propose and experimentally demonstrate a novel ultra-long range and sensitive distributed fiber vibration sensor. Only one unidirectional Mach-Zehnder interferometer (MZI) is employed in this scheme as the sensing element. In this sensor structure, we utilize chromatic dispersion-induced walk-off effect between the vibration signals sensed by two distributed feedback (DFB) lasers at different wavelengths to locate the vibration position. Vibration signals with frequencies up to 9 MHz can be detected and the spatial resolution of 31 m is achieved over 320 km of the standard single mode fiber. Monitoring multiple vibration sources can also be realized using this scheme.

  14. Destabilization analysis of overlapping underground chambers induced by blasting vibration with catastrophe theory

    Institute of Scientific and Technical Information of China (English)

    YAN Chang-bin; XU Guo-yuan; ZUO Yu-jun

    2006-01-01

    According to the main characters of overlapping underground chambers, the roof (floor) of two adjacent underground chambers is simplified to the mechanical model that is the beam with build-in ends. And vibration load due to blasting is simplified to harmonic wave. The catastrophic model of double cusp for underground chambers destabilization induced by blasting vibration has been established under the circumstances of considering deadweight of the beam, and the condition of destabilization has been worked out. The critical safety thickness of the roof (floor) of underground chambers has been confirmed according to the destabilization condition. The influence of amplitude and frequency of blasting vibration load on the critical safety thickness has been analyzed, and the quantitative relation between velocity, frequency of blasting vibration and critical safety thickness has been determined. Research results show that the destabilization of underground chambers is not only dependent on the amplitude and frequency of blasting vibration load, but also related to deadweight load and intrinsic attribute. It is accordant to testing results and some related latest research results of blasting seismic effect. With increasing amplitude, the critical safety thickness of underground chambers decreases gradually. And the possibility of underground chambers destabilization increases. When the frequency of blasting vibration is equal to or very close to the frequency of beam, resonance effect will take place in the system. Then the critical safety thickness will turn to zero, underground chambers will be damaged severely, and its loading capacity will lose on the whole.

  15. Metro train-induced vibrations on historic buildings in Chengdu, China

    Institute of Scientific and Technical Information of China (English)

    Meng MA; Valéri MARKINE; Wei-ning LIU; Yang YUAN; Feng ZHANG

    2011-01-01

    In this paper,the vibration influence on a monument caused by Chengdu Subway Line 2 is analyzed.Due to its elaborate and unique design,both structural and architectural damages should be avoided.First,the allowable root mean square (RMS) velocity at the foundation of the monument is derived and a site measurement is performed to obtain the background vibrations induced by road traffic.In addition,a train-track coupled model and 3D tunnel-soil-structure coupled finite element models are built to predict the dynamic response of the monument.Prediction models are checked by site measurement in Beijing Subway Line 5.Different kinds of fasteners and train speeds are compared and discussed as well.Results show that:(1) At a train speed of 72 km/h,all the traffic vibrations exceed the low limit no matter what kind of fastener is used,which is mainly due to the contribution of road traffic.Slowing down train speeds can cause effective vibration attenuation; (2) Vibrations drop dramatically with the train speed from 65 to 58 krn/h.When the train speed is lower than 58 km/h,vibrations are lower than allowable value even if the contribution of road traffic is considered.

  16. Light-induced vibration characteristics of free-standing carbon nanotube films fabricated by vacuum filtration

    Energy Technology Data Exchange (ETDEWEB)

    Li, Junying; Zhu, Yong, E-mail: yongzhu@cqu.edu.cn; Wang, Ning; Zhang, Jie [The Key Laboratory of Optoelectronic Technology and System, Education Ministry of China, Chongqing University, Chongqing, 400044 (China); Wang, Xin [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054 (China)

    2014-07-14

    In this paper, we fabricated carbon nanotube (CNT) films with different thickness by vacuum filtration method, and the films were separated from Mixed Cellulose Ester membranes with burn-off process. The thickness of CNT films with different concentrations of CNTs 50 mg, 100 mg, 150 mg, and 200 mg are 10.36 μm, 20.90 μm, 30.19 μm, and 39.98 μm respectively. The CNT bundles are homogeneously distributed and entangled with each other, and still maintain 2D continuous network structures after burn-off process. The optical absorptivity of the films is between 84% and 99% at wavelengths ranging from 400 nm to 2500 nm. Vibration characteristics were measured with the Fabry-Perot (F-P) interferometer vibration measurement system. CNT films vibrate only under the xenon light irradiating perpendicularly to the surface. Vibration recorded by Fabry-Perot interferometer is considered to be caused by the time-dependent thermal moment, which is due to the temperature differences of two sides of CNT films. The vibration frequency spectrums between 0.1 ∼ 0.5 Hz were obtained by the Fast Fourier Transform spectra from time domain to frequency domain, and showed a linear relationship with films thickness, which is in accordance with theoretical model of thermal induced vibration.

  17. Physical and numerical investigation of the flow induced vibration of the hydrofoil

    Science.gov (United States)

    Wu, Q.; Wang, G. Y.; Huang, B.

    2016-11-01

    The objective of this paper is to investigate the flow induced vibration of a flexible hydrofoil in cavitating flows via combined experimental and numerical studies. The experiments are presented for the modified NACA66 hydrofoil made of POM Polyacetate in the closed-loop cavitation tunnel at Beijing Institute of Technology. The high-speed camera and the single point Laser Doppler Vibrometer are applied to analyze the transient flow structures and the corresponding structural vibration characteristics. The hybrid coupled fluid structure interaction model is conducted to couple the incompressible and unsteady Reynolds Averaged Navier-Stokes solver with a simplified two-degree-of-freedom structural model. The k-ω SST turbulence model with the turbulence viscosity correction and the Zwart cavitation model are introduced to the present simulations. The results showed that with the decreasing of the cavitation number, the cavitating flows display incipient cavitation, sheet cavitation, cloud cavitation and supercavitation. The vibration magnitude increases dramatically for the cloud cavitation and decline for the supercavitation. The cloud cavitation development strongly affects the vibration response, which is corresponding to the periodically developing and shedding of the large-scale cloud cavity. The main frequency of the vibration amplitude is accordance with the cavity shedding frequency and other two frequencies of the vibration amplitude are corresponding to the natural frequencies of the bending and twisting modes.

  18. Investigation into the vibration of metro bogies induced by rail corrugation

    Science.gov (United States)

    Ling, Liang; Li, Wei; Foo, Elbert; Wu, Lei; Wen, Zefeng; Jin, Xuesong

    2017-01-01

    The current research of rail corrugation mainly focuses on the mechanisms of its formation and development. Compared with the root causes and development mechanisms, the wheel-rail impacts, the fatigue failure of vehicle-track parts, and the loss of ride comfort due to rail corrugation should also be taken into account. However, the influences of rail corrugation on vehicle and track vibration, and failure of vehicle and track structural parts are barely discussed in the literature. This paper presents an experimental and numerical investigation of the structural vibration of metro bogies caused by rail corrugation. Extensive experiments are conducted to investigate the effects of short-pitch rail corrugation on the vibration accelerations of metro bogies. A dynamic model of a metro vehicle coupled with a concrete track is established to study the influence of rail corrugation on the structural vibration of metro bogies. The field test results indicate that the short-pitch rail corrugation generates strong vibrations on the axle-boxes and the bogie frames, therefore, accelerates the fatigue failure of the bogie components. The numerical results show that short-pitch rail corrugation may largely reduce the fatigue life of the coil spring, and improving the damping value of the primary vertical dampers is likely to reduce the strong vibration induced by short-pitch rail corrugation. This research systematically studies the effect of rail corrugation on the vibration of metro bogies and proposes some remedies for mitigating strong vibrations of metro bogies and reducing the incidence of failure in primary coil springs, which would be helpful in developing new metro bogies and track maintenance procedures.

  19. Periodicity-induced effects and method in vibro-acoustics

    DEFF Research Database (Denmark)

    Sorokin, Sergey V.

    2014-01-01

    The lecture is concerned with the modelling of wave propagation in and vibration of periodic elastic structures. Although analysis of wave-guide properties of infinite periodic structures is a well establish research subject, some issues have not yet been fully addressed in the literature. The aim...... paid to eigenfrequencies of a single periodicity cell with various boundary conditions. Another issue addressed in the lecture is an influence of the corrugation shape and amplitude on the broadness and location of the stop- and pass-bands in an infinite periodic structure. The concluding part...

  20. A Numerical Study on the Screening of Blast-Induced Waves for Reducing Ground Vibration

    Science.gov (United States)

    Park, Dohyun; Jeon, Byungkyu; Jeon, Seokwon

    2009-06-01

    Blasting is often a necessary part of mining and construction operations, and is the most cost-effective way to break rock, but blasting generates both noise and ground vibration. In urban areas, noise and vibration have an environmental impact, and cause structural damage to nearby structures. Various wave-screening methods have been used for many years to reduce blast-induced ground vibration. However, these methods have not been quantitatively studied for their reduction effect of ground vibration. The present study focused on the quantitative assessment of the effectiveness in vibration reduction of line-drilling as a screening method using a numerical method. Two numerical methods were used to analyze the reduction effect toward ground vibration, namely, the “distinct element method” and the “non-linear hydrocode.” The distinct element method, by particle flow code in two dimensions (PFC 2D), was used for two-dimensional parametric analyses, and some cases of two-dimensional analyses were analyzed three-dimensionally using AUTODYN 3D, the program of the non-linear hydrocode. To analyze the screening effectiveness of line-drilling, parametric analyses were carried out under various conditions, with the spacing, diameter of drill holes, distance between the blasthole and line-drilling, and the number of rows of drill holes, including their arrangement, used as parameters. The screening effectiveness was assessed via a comparison of the vibration amplitude between cases both with and without screening. Also, the frequency distribution of ground motion of the two cases was investigated through fast Fourier transform (FFT), with the differences also examined. From our study, it was concluded that line-drilling as a screening method of blast-induced waves was considerably effective under certain design conditions. The design details for field application have also been proposed.

  1. Numerical Modelling of Rain-Wind-Induced Vibration: Erasmus Bridge, Rotterdam

    NARCIS (Netherlands)

    Geurts, C.; Vrouwenvelder, T.; Staalduinen, P.C. van; Reusink, J.

    1998-01-01

    Shortly after completion, the main span cables of the Erasmus Bridge in Rotterdam showed aerodynamic instabilities with large amplitudes. These instabilities were recognised as rain-wind-induced vibrations. Temporary measures were installed on the bridge, and a year later, tuned hydraulic dampers we

  2. Vibration-induced displacement using high-frequency resonators and friction layers

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel

    1998-01-01

    A mathematical model is set up to quantify vibration-induced motions of a slider with an imbedded resonator. A simple approximate expression is presented for predicting average velocities of the slider, agreeing fairly well with numerical integration of the full equations of motion. The simple...... expression can be used to the estimate influence of system parameters, and to plan and interpret laboratory experiments....

  3. Wind-induced vibration control of Hefei TV tower with fluid viscous damper

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhiqiang; Aiqun LI; Jianping HE; Jianlei WANG

    2009-01-01

    The Hefei TV tower is taken as an analytical case to examine the control method with a fluid viscous damper under wind load fluctuation. Firstly, according to the random vibration theory, the effect of fluctuating wind on the tower can be modeled as a 19-dimensional correlated random process, and the wind-induced vibration analysis of the tower subjected to dynamic wind load was further obtained. On the basis of the others' works, a bi-model dynamic model is proposed. Finally, a dynamic model is proposed to study the wind-induced vibration control analysis using viscous fluid dampers, and the optimal damping coefficient is obtained regarding the wind-induced response of the upper turret as optimization objectives. Analysis results show that the maximum peak response of the tower under dynamic wind load is far beyond the allowable range of the code. The wind-induced responses and the wind vibration input energy of the tower are decreased greatly by using a fluid viscous damper, and the peak acceleration responses of the upper turret is reduced by 43.4%.

  4. Flow induced vibration of subsea gas production systems caused by choke valves

    NARCIS (Netherlands)

    Ligterink, N.E.; Groot, R. de; Gharaibah, E.; Slot, H.J.

    2012-01-01

    In the design of subsea flow systems the integrity and reliability is paramount. As the equipment must be designed to operate at a large variety of conditions, inherent to the many processes, evaluation of the integrity is complex. . Flow induced pulsations and vibrations can cause serious design an

  5. Flow induced vibration of subsea gas production system caused by choke valves

    NARCIS (Netherlands)

    Ligterink, N.E.; Groot, R. de; Gharaibah, E.; Slot, H.J.

    2012-01-01

    In the design of subsea flow systems the integrity and reliability is paramount. As the equipment must be designed to operate at a large variety of conditions, inherent to the many processes, evaluation of the integrity is complex. . Flow induced pulsations and vibrations can cause serious design an

  6. Vibration-induced field fluctuations in a superconducting magnet

    CERN Document Server

    Britton, J W; Bohnet, J G; Uys, H; Biercuk, M J; Bollinger, J J

    2015-01-01

    Superconducting magnets enable precise control of nuclear and electron spins, and are used in experiments that explore biological and condensed matter systems, and fundamental atomic particles. In high-precision applications, a common view is that that slow (<1 Hz) drift of the homogeneous magnetic field limits control and measurement precision. We report on previously undocumented higher-frequency field noise (10 Hz to 200 Hz) that limits the coherence time of 9Be+ electron-spin qubits in the 4.46 T field of a superconducting magnet. We measure a spin-echo T2 coherence time of ~6 ms for the 9Be+ electron-spin resonance at 124 GHz, limited by part-per-billion fractional fluctuations in the magnet's homogeneous field. Vibration isolation of the magnet improved T2 to ~50 ms.

  7. Regarding "A new method for predicting nonlinear structural vibrations induced by ground impact loading" [Journal of Sound and Vibration, 331/9 (2012) 2129-2140

    Science.gov (United States)

    Cartmell, Matthew P.

    2016-09-01

    The Editor wishes to make the reader aware that the paper "A new method for predicting nonlinear structural vibrations induced by ground impact loading" by Jun Liu, Yu Zhang, Bin Yun, Journal of Sound and Vibration, 331 (2012) 2129-2140, did not contain a direct citation of the fundamental and original work in this field by Dr. Mark Svinkin. The Editor regrets that this omission was not noted at the time that the above paper was accepted and published.

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

    DEFF Research Database (Denmark)

    Matteoni, Giulia; Georgakis, Christos

    2010-01-01

    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......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 randomness of crowds travelling across the footbridge. Moreover, the codes, for most of the part, do not deal with pedestrian loading other than walking, even though running and jumping can often produce larger loads and vibration amplitudes. In this paper, an investigation inot the response of footbridges...... into account variations in the structural characteristics, crowd morphology and return period. The correction factors, together with the reference acceleration, are used to determine the final response of the footbridge, for a given probability of load occurrence....

  9. Effect of vehicle weight on natural frequencies of bridges measured from traffic-induced vibration

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Recently, ambient vibration test (AVT) is widely used to estimate dynamic characteristics of large civil structures. Dynamic characteristics can be affected by various environmental factors such as humidity, intensity of wind, and temperature. Besides these environmental conditions, the mass of vehicles may change the measured values when traffic-induced vibration is used as a source of AVT for bridges. The effect of vehicle mass on dynamic characteristics is investigated through traffic-induced vibration tests on three bridges; (1) three-span suspension bridge (128m+404m+128m), (2) five-span continuous steel box girder bridge (59m+3@95m+59m), (3) simply supported plate girder bridge (46m). Acceleration histories of each measurement location under normal traffic are recorded for 30 minutes at field. These recorded histories are divided into individual vibrations and are combined into two groups according to the level of vibration; one by heavy vehicles such as trucks and buses and the other by light vehicles such as passenger cars. Separate processing of the two groups of signals shows that, for the middle and long-span bridges, the difference can be hardly detected, but, for the short span bridges whose mass is relatively small, the measured natural frequencies can change up to 5.4%.

  10. Shellside flow-induced tube vibration in typical heat exchanger configurations: overview of a research program

    Energy Technology Data Exchange (ETDEWEB)

    Halle, H.; Chenoweth, J.M.; Wambsganss, M.W.

    1986-01-01

    A comprehensive research program is being conducted to develop the necessary criteria to assist designers and operators of shell-and-tube heat exchangers to avoid detrimental flow-induced tube vibration. This paper presents an overview of the insights gained from shellside water-flow testing on a horizontal, industrial-sized test exchanger that can be configured in many ways using interchangeable tube bundles and replaceable nozzles. Nearly 50 different configurations have been tested representing various combinations of triangular, square, rotated-triangular, and rotated-square tubefield layouts; odd and even numbers of crosspasses; and both single- and double-segmental baffles with different cut sizes and orientations. The results are generally consistent with analytical relationships that predict tube vibration response by the combined reinforcing effect of the vibration mode shape and flow velocity distribution. An understanding of the vibration and instability performance is facilitated by recognizing that the excitation is induced by three separate, though sometimes interacting, flow conditions. These are the crossflows that generate ''classic'' fluidelastic instabilities in the interior of the tube bundle, the entrance and exit bundle flow from and into the shell nozzles, and the localized high velocity bypass and leakage stream flows. The implications to design and/or possible field remedies to avoid vibration problems are discussed. 17 refs., 10 figs.

  11. Whole-body vibration training induces hypertrophy of the human patellar tendon.

    Science.gov (United States)

    Rieder, F; Wiesinger, H-P; Kösters, A; Müller, E; Seynnes, O R

    2016-08-01

    Animal studies suggest that regular exposure to whole-body vibration (WBV) induces an anabolic response in bone and tendon. However, the effects of this type of intervention on human tendon properties and its influence on the muscle-tendon unit function have never been investigated. The aim of this study was to investigate the effect of WBV training on the patellar tendon mechanical, material and morphological properties, the quadriceps muscle architecture and the knee extension torque-angle relationship. Fifty-five subjects were randomized into either a vibration, an active control, or an inactive control group. The active control subjects performed isometric squats on a vibration platform without vibration. Muscle and tendon properties were measured using ultrasonography and dynamometry. Vibration training induced an increase in proximal (6.3%) and mean (3.8%) tendon cross-sectional area, without any appreciable change in tendon stiffness and modulus or in muscle architectural parameters. Isometric torque at a knee angle of 90° increased in active controls (6.7%) only and the torque-angle relation remained globally unchanged in all groups. The present protocol did not appreciably alter knee extension torque production or the musculo-tendinous parameters underpinning this function. Nonetheless, this study shows for the first time that WBV elicits tendon hypertrophy in humans.

  12. Assessing the underwater acoustics of the world's largest vibration hammer (OCTA-KONG and its potential effects on the Indo-Pacific humpbacked dolphin (Sousa chinensis.

    Directory of Open Access Journals (Sweden)

    Zhitao Wang

    Full Text Available Anthropogenic noise in aquatic environments is a worldwide concern due to its potential adverse effects on the environment and aquatic life. The Hongkong-Zhuhai-Macao Bridge is currently under construction in the Pearl River Estuary, a hot spot for the Indo-Pacific humpbacked dolphin (Sousa chinensis in China. The OCTA-KONG, the world's largest vibration hammer, is being used during this construction project to drive or extract steel shell piles 22 m in diameter. This activity poses a substantial threat to marine mammals, and an environmental assessment is critically needed. The underwater acoustic properties of the OCTA-KONG were analyzed, and the potential impacts of the underwater acoustic energy on Sousa, including auditory masking and physiological impacts, were assessed. The fundamental frequency of the OCTA-KONG vibration ranged from 15 Hz to 16 Hz, and the noise increments were below 20 kHz, with a dominant frequency and energy below 10 kHz. The resulting sounds are most likely detectable by Sousa over distances of up to 3.5 km from the source. Although Sousa clicks do not appear to be adversely affected, Sousa whistles are susceptible to auditory masking, which may negatively impact this species' social life. Therefore, a safety zone with a radius of 500 m is proposed. Although the zero-to-peak source level (SL of the OCTA-KONG was lower than the physiological damage level, the maximum root-mean-square SL exceeded the cetacean safety exposure level on several occasions. Moreover, the majority of the unweighted cumulative source sound exposure levels (SSELs and the cetacean auditory weighted cumulative SSELs exceeded the acoustic threshold levels for the onset of temporary threshold shift, a type of potentially recoverable auditory damage resulting from prolonged sound exposure. These findings may aid in the identification and design of appropriate mitigation methods, such as the use of air bubble curtains, "soft start" and "power down

  13. Assessing the underwater acoustics of the world's largest vibration hammer (OCTA-KONG) and its potential effects on the Indo-Pacific humpbacked dolphin (Sousa chinensis).

    Science.gov (United States)

    Wang, Zhitao; Wu, Yuping; Duan, Guoqin; Cao, Hanjiang; Liu, Jianchang; Wang, Kexiong; Wang, Ding

    2014-01-01

    Anthropogenic noise in aquatic environments is a worldwide concern due to its potential adverse effects on the environment and aquatic life. The Hongkong-Zhuhai-Macao Bridge is currently under construction in the Pearl River Estuary, a hot spot for the Indo-Pacific humpbacked dolphin (Sousa chinensis) in China. The OCTA-KONG, the world's largest vibration hammer, is being used during this construction project to drive or extract steel shell piles 22 m in diameter. This activity poses a substantial threat to marine mammals, and an environmental assessment is critically needed. The underwater acoustic properties of the OCTA-KONG were analyzed, and the potential impacts of the underwater acoustic energy on Sousa, including auditory masking and physiological impacts, were assessed. The fundamental frequency of the OCTA-KONG vibration ranged from 15 Hz to 16 Hz, and the noise increments were below 20 kHz, with a dominant frequency and energy below 10 kHz. The resulting sounds are most likely detectable by Sousa over distances of up to 3.5 km from the source. Although Sousa clicks do not appear to be adversely affected, Sousa whistles are susceptible to auditory masking, which may negatively impact this species' social life. Therefore, a safety zone with a radius of 500 m is proposed. Although the zero-to-peak source level (SL) of the OCTA-KONG was lower than the physiological damage level, the maximum root-mean-square SL exceeded the cetacean safety exposure level on several occasions. Moreover, the majority of the unweighted cumulative source sound exposure levels (SSELs) and the cetacean auditory weighted cumulative SSELs exceeded the acoustic threshold levels for the onset of temporary threshold shift, a type of potentially recoverable auditory damage resulting from prolonged sound exposure. These findings may aid in the identification and design of appropriate mitigation methods, such as the use of air bubble curtains, "soft start" and "power down" techniques.

  14. Experimental investigation of railway train-induced vibrations of surrounding ground and a nearby multi-story building

    Institute of Scientific and Technical Information of China (English)

    Xia He; Chen Jianguo; Wei Pengbo; Xia Chaoyi; G. De Roeck; G. Degrande

    2009-01-01

    In this paper, a field experiment was carried out to study train-induced environmental vibrations. During the field experiment, velocity responses were measured at different locations of a six-story masonry structure near the Beijing- Guangzhou Railway and along a small road adjacent to the building. The results show that the velocity response levels of the environmental ground and the building floors increase with train speed, and attenuate with the distance to the railway track. Heavier freight trains induce greater vibrations than lighter passenger trains. In the multi-story building, the lateral velocity levels increase monotonically with floor elevation, while the vertical ones increase with floor elevation in a fluctuating manner. The indoor floor vibrations are much lower than the outdoor ground vibrations. The lateral vibration of the building along the direction of weak structural stiffness is greater than along the direction with stronger stiffness. A larger room produces greater floor vibrations than the staircase at the same elevation, and the vibration at the center of a room is greater than at its comer. The vibrations of the building were compared with the Federal Transportation Railroad Administration (FTA) criteria for acceptable ground-borne vibrations expressed in terms ofrms velocity levels in decibels. The results show that the train-induced building vibrations are serious, and some exceed the allowance given in relevant criterion.

  15. Music-induced emotions can be predicted from a combination of brain activity and acoustic features.

    Science.gov (United States)

    Daly, Ian; Williams, Duncan; Hallowell, James; Hwang, Faustina; Kirke, Alexis; Malik, Asad; Weaver, James; Miranda, Eduardo; Nasuto, Slawomir J

    2015-12-01

    It is widely acknowledged that music can communicate and induce a wide range of emotions in the listener. However, music is a highly-complex audio signal composed of a wide range of complex time- and frequency-varying components. Additionally, music-induced emotions are known to differ greatly between listeners. Therefore, it is not immediately clear what emotions will be induced in a given individual by a piece of music. We attempt to predict the music-induced emotional response in a listener by measuring the activity in the listeners electroencephalogram (EEG). We combine these measures with acoustic descriptors of the music, an approach that allows us to consider music as a complex set of time-varying acoustic features, independently of any specific music theory. Regression models are found which allow us to predict the music-induced emotions of our participants with a correlation between the actual and predicted responses of up to r=0.234,pemotions can be predicted by their neural activity and the properties of the music. Given the large amount of noise, non-stationarity, and non-linearity in both EEG and music, this is an encouraging result. Additionally, the combination of measures of brain activity and acoustic features describing the music played to our participants allows us to predict music-induced emotions with significantly higher accuracies than either feature type alone (p<0.01).

  16. Excited and enhanced twinborn acoustic-induced mutual forces in oblique grating structures

    Science.gov (United States)

    Lu, Shuifang; Zhang, Xin; Wu, Fugen; Yao, Yuanwei; Chen, Zongwang

    2016-07-01

    We propose a water-immersed geometrically oblique grating structure patterned with a 1D periodic array of oblique rhombuses. Twin acoustic-induced mutual forces (both repulsive and attractive) between coupled steel plates were realized in this system when the external plane wave normally impacted the plates. Calculations showed that the emerging forces are more than an order of magnitude larger than the corresponding induced force of a conventional grating structure. We also found that the strong acoustic-induced mutual forces stem from the resonant excitation of nonleaky flexural Lamb modes in the coupled plates, and that these forces couple more strongly with the external incident acoustic waves. Furthermore, the amplitudes and resonant wavelengths of these forces can be coarsely controlled by changing the symmetry of the system and finely adjusted by varying the slant angle and the edge-length of the oblique rhombus. The proposed acoustic system could potentially be applied in sensors and in the ultrasonic detection of weak signals in water.

  17. Flow-induced noise simulation using detached eddy simulation and the finite element acoustic analogy method

    Directory of Open Access Journals (Sweden)

    Kai Liu

    2016-06-01

    Full Text Available Signals in long-distance pipes are complex due to flow-induced noise generated in special structure, and the computation of these noise sources is difficult and time-consuming. To address this problem, a hybrid method based on computational fluid dynamics and Lighthill’s acoustic analogy theory is proposed to simulate flow-induced noise, with the results showing that the method is sufficient for noise predictions. The proposed method computes the turbulent flow field using detached eddy simulation and then calculates turbulence-generated sound using the finite element acoustic analogy method, which solves acoustic sources as volume sources. The velocity field obtained in the detached eddy simulation computation provides the sound source through interpolation between the computational fluid dynamics and acoustic meshes. The hybrid method is validated and assessed by comparing data from the cavity in pipe and large eddy simulation results. The peak value of flow-induced noise calculated at the monitor point is in good agreement with experimental data available in the literature.

  18. Wind tunnel study on wind-induced vibration of middle pylon of Taizhou Bridge

    Institute of Scientific and Technical Information of China (English)

    Ma Rujin; Zhang Zhen; Chen Airong

    2012-01-01

    Full aero-elastic model tests are carried out to investigate wind-induced vibration of middle steel pylon of Taizhou Bridge. Model of the pylon under different construction periods is tested in both uniform and turbulent flow field. And the yaw angle of wind changes from transverse to longitudinal. Through full aero-elastic model testing, windinduced vibration is checked, which includes vortex resonance, buffeting and galloping. Vortex resonance is observed and further studies are carried out by changing damping ratio. Based on wind tunnel testing results, wind-resistance of middle pylon is evaluated and some suggestions are given for middle pylon' s construction.

  19. Sliding mode control of wind-induced vibrations using fuzzy sliding surface and gain adaptation

    Science.gov (United States)

    Thenozhi, Suresh; Yu, Wen

    2016-04-01

    Although fuzzy/adaptive sliding mode control can reduce the chattering problem in structural vibration control applications, they require the equivalent control and the upper bounds of the system uncertainties. In this paper, we used fuzzy logic to approximate the standard sliding surface and designed a dead-zone adaptive law for tuning the switching gain of the sliding mode control. The stability of the proposed controller is established using Lyapunov stability theory. A six-storey building prototype equipped with an active mass damper has been used to demonstrate the effectiveness of the proposed controller towards the wind-induced vibrations.

  20. State-space approach to vibration of gold nano-beam induced by ramp type heating

    Institute of Scientific and Technical Information of China (English)

    Hamdy M Youssef; Khaled A Elsibai

    2010-01-01

    In the nanoscale beam, two effects become domineering. One is the non-Fourier effect in heat conduction and the other is the coupling effect between temperature and strain rate. In the present study, a generalized solution for the generalized thermoelastic vibration of gold nano-beam resonator induced by ramp type heating is developed. The solution takes into account the above two effects. State-space and Laplace transform methods are used to determine the lateral vibration, the temperature, the displacement, the stress and the strain energy of the beam. The effects of the relaxation time and the ramping time parameters have been studied.

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

    Directory of Open Access Journals (Sweden)

    Jiang Ren-Jie

    2012-01-01

    Full Text Available 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 cylinder, the gap flow plays an important role. As the separation ratio is increased, the fluid-structure interaction decouples and the cylinders behave as two isolated cylinders.

  2. On The Analysis of Labyrinth Seal Flow Induced Vibration by Oscillating Fluid Mechanics Method

    Institute of Scientific and Technical Information of China (English)

    ChenZuoyi; JingYouhao; 等

    1994-01-01

    A numerical model and a solution method to analyze the labyrinth seal flow induced vibration by Oscillating Fluid Mechanics Method(OFMM) are presented in this paper,including the basic equations and solution procedure to determine the oscillating velocity,pressure and the dynamic characteristic coefficients of Labyrinth seal such as the stiffness coefficients and damping coefficients.The results show that this method has the advantages of both less time consuming and high accuracy.In addition it can be applied to the field diagnosis of the vibration of the axis of turbomachinery system.

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

    DEFF Research Database (Denmark)

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

    2014-01-01

    This work presents an analysis of two-dimensional (2D) and three-dimensional (3D) non-moving, prescribed motion and elastically mounted airfoil computational fluid dynamics (CFD) computations. The elastically mounted airfoil computations were performed by means of a 2D structural model with two d...... are 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....

  4. Correlation between microbubble-induced acoustic cavitation and hemolysis in vitro

    Institute of Scientific and Technical Information of China (English)

    Zhang Chun-Bing; Liu Zheng; Guo Xia-Sheng; Zhang Dong

    2011-01-01

    Microbubbles promise to enhance the efficiency of ultrasound-mediated drug delivery and gene therapy by taking advantage of artificial cavitation nuclei. The purpose of this study is to examine the ultrasound-induced hemolysis in the application of drug delivery in the presence of microbubbles. To achieve this goal, human red blood cells mixed with microbubbles were exposed to 1-MHz pulsed ultrasound. The hemolysis level was measured by a flow cytometry, and the cavitation dose was detected by a passive cavitation detecting system. The results demonstrate that larger cavitation dose would be generated with the increase of acoustic pressure, which might give rise to the enhancement of hemolysis. Besides the experimental observations, the acoustic pressure dependence of the radial oscillation of microbubble was theoretically estimated. The comparison between the experimental and calculation results indicates that the hemolysis should be highly correlated to the acoustic cavitation.

  5. Determination of blast-induced ground vibration equations for rocks using mechanical and geological properties

    Institute of Scientific and Technical Information of China (English)

    Ranjan Kumar; Deepankar Choudhury; Kapilesh Bhargava

    2016-01-01

    In the recent decades, effects of blast loads on natural and man-made structures have gained considerable attention due to increase in threat from various man-made activities. Site-specific empirical relationships for calculation of blast-induced vibration parameters like peak particle velocity (PPV) and peak particle displacement (PPD) are commonly used for estimation of blast loads in design. However, these relation-ships are not able to consider the variation in rock parameters and uncertainty of in situ conditions. In this paper, a total of 1089 published blast data of various researchers in different rock sites have been collected and used to propose generalized empirical model for PPV by considering the effects of rock parameters like unit weight, rock quality designation (RQD), geological strength index (GSI), and uniaxial compressive strength (UCS). The proposed PPV model has a good correlation coefficient and hence it can be directly used in prediction of blast-induced vibrations in rocks. Standard errors and coefficient of correlations of the predicted blast-induced vibration parameters are obtained with respect to the observed field data. The proposed empirical model for PPV has also been compared with the empirical models available for blast vibrations predictions given by other researchers and found to be in good agreement with specific cases.

  6. The Influence of Acoustic Field Induced by HRT on Oscillation Behavior of a Single Droplet

    Directory of Open Access Journals (Sweden)

    Can Ruan

    2017-01-01

    Full Text Available This paper presents an experimental and theoretical study on the effects of an acoustic field induced by Hartmann Resonance Tube (HRT on droplet deformation behavior. The characteristics of the acoustic field generated by HRT are investigated. Results show that the acoustic frequency decreases with the increase of the resonator length, the sound pressure level (SPL increases with the increase of nozzle pressure ratio (NPR, and it is also noted that increasing resonator length can cause SPL to decrease, which has rarely been reported in published literature. Further theoretical analysis reveals that the resonance frequency of a droplet has several modes, and when the acoustic frequency equals the droplet’s frequency, heightened droplet responses are observed with the maximum amplitude of the shape oscillation. The experimental results for different resonator cavity lengths, nozzle pressure ratios and droplet diameters confirm the non-linear nature of this problem, and this conclusion is in good agreement with theoretical analysis. Measurements by high speed camera have shown that the introduction of an acoustic field can greatly enhance droplet oscillation, which means with the use of an ultrasonic atomizer based on HRT, the quality of atomization and combustion can be highly improved.

  7. Vibration-Induced Droplet Atomization --- A Theoretical Investigation.

    Science.gov (United States)

    James, Ashley; Smith, Marc K.; Glezer, Ari

    1997-11-01

    The atomization of a liquid droplet placed on a vibrating membrane starts with the development of Faraday free surface waves. As the excitation amplitude increases, the waves grow in amplitude and ultimately begin to eject smaller secondary droplets from the wave crests. The rate of droplet ejection can be large enough to completely drain the primary droplet, an event we call bursting. The evolution of the droplet ejection process depends on a coupled system dynamic between the droplet and the membrane. When droplets are ejected the resonant frequency of the system increases. This changes the acceleration felt by the droplet and, in turn, the rate of droplet ejection. Depending on the excitation frequency and amplitude, various types of bursting or droplet ejection processes may occur. A simple, single degree-of-freedom model of this coupled system is presented. The model is used to illustrate the effect of the excitation frequency and amplitude and the initial droplet size on the acceleration of the membrane and the droplet ejection rate. The results of the model will be compared to our experimental data on droplet ejection. Additional work is directed towards an understanding of the mechanism behind the droplet ejection process.

  8. Vibration-Induced Droplet Atomization --- An Experimental Investigation.

    Science.gov (United States)

    Vukasinovic, Bojan; Smith, Marc K.; Glezer, Ari

    1997-11-01

    The atomization of a liquid droplet placed on a vibrating membrane starts with the development of Faraday free surface waves. As the excitation amplitude increases, the waves grow in amplitude and ultimately begin to eject smaller secondary droplets from the wave crests. The rate of droplet ejection can be large enough to completely drain the primary droplet, an event we call bursting. The evolution of the droplet ejection process depends on a coupled system dynamic between the droplet and the membrane. When droplets are ejected the resonant frequency of the system increases. This changes the acceleration felt by the droplet and, in turn, the rate of droplet ejection. Depending on the excitation frequency and amplitude, various types of bursting or droplet ejection processes may occur. In the present experiments, the high acceleration needed to attain ejection (typically 300g) is achieved by driving a light-weight membrane near its resonant frequency (nominally 1000 Hz). The resonant characteristics and the acceleration during the ejection process for various droplet sizes and excitation amplitudes are investigated using a surface-mounted microfabricated accelerometer and a laboratory computer system.

  9. Combined Annoyance Assessment of Subway Train-Induced Structural Vibration and Ambient Noise

    Directory of Open Access Journals (Sweden)

    Ke Sun

    2016-01-01

    Full Text Available The subway train-induced structural vibration and ambient noise may cause annoyance and other negative influences on the human body. Presently, limited models have been developed to execute the quantitative evaluation of the combined annoyance caused by both structural vibration and ambient noise. In this study, a fuzzy membership function and normal distribution function were coupled to describe the fuzziness and randomness of human annoyance responses; a novel annoyance evaluation model was proposed to assess the structural vibration and ambient noise; and the annoyance of human was classified into six grades. Subsequently, we integrated an actual case into this study to calculate and analyze the combined annoyance degree. The applied results were compared with the standard limits, in which the rationality and superiority of the proposed model were verified. The results exhibit the notion that the proposed models perform well and can serve as a reference for spatial planning and development in the nearby subway environment.

  10. Vulnerability Assessment for a Complex Structure Using Vibration Response Induced by Impact Load

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jeongwon; Park, Junhong [Hanyang University, Seoul (Korea, Republic of); Koo, Man Hoi [Agency for Defense Development, Daejeon (Korea, Republic of)

    2014-10-15

    This work presents a vulnerability assessment procedure for a complex structure using vibration characteristics. The structural behavior of a three-dimensional framed structure subjected to impact forces was predicted using the spectral element method. The Timoshenko beam function was applied to simulate the impact wave propagations induced by a high-velocity projectile at relatively high frequencies. The interactions at the joints were analyzed for both flexural and longitudinal wave propagations. Simulations of the impact energy transfer through the entire structure were performed using the transient displacement and acceleration responses obtained from the frequency analysis. The kill probabilities of the crucial components for an operating system were calculated as a function of the predicted acceleration amplitudes according to the acceptable vibration levels. Following the proposed vulnerability assessment procedure, the vulnerable positions of a three-dimensional combat vehicle with high possibilities of damage generation of components by impact loading were identified from the estimated vibration responses.

  11. Simulation of vibration-induced effect on plasma current measurement using a fiber optic current sensor.

    Science.gov (United States)

    Descamps, Frédéric; Aerssens, Matthieu; Gusarov, Andrei; Mégret, Patrice; Massaut, Vincent; Wuilpart, Marc

    2014-06-16

    An accurate measurement of the plasma current is of paramount importance for controlling the plasma magnetic equilibrium in tokamaks. Fiber optic current sensor (FOCS) technology is expected to be implemented to perform this task in ITER. However, during ITER operation, the vessel and the sensing fiber will be subject to vibrations and thus to time-dependent parasitic birefringence, which may significantly compromise the FOCS performance. In this paper we investigate the effects of vibrations on the plasma current measurement accuracy under ITER-relevant conditions. The simulation results show that in the case of a FOCS reflection scheme including a spun fiber and a Faraday mirror, the error induced by the vibrations is acceptable regarding the ITER current diagnostics requirements.

  12. Stern-Gerlach Experiments on Mn@Sn12: Identification of a Paramagnetic Superatom and Vibrationally Induced Spin Orientation

    Science.gov (United States)

    Rohrmann, Urban; Schäfer, Rolf

    2013-09-01

    Beam deflection experiments in inhomogeneous magnetic fields reveal a new limiting case of the magnetization distribution of isolated clusters. Endohedrally doped clusters are produced in a temperature controlled, cryogenically cooled laser ablation source. Temperature dependent experiments indicate a crucial contribution of molecular vibrations to the spin dynamics of Mn@Sn12. In its vibrational ground state the cluster behaves magnetically like a paramagnetic atom, with quantized spin states. However, excited molecular vibrations induce spin orientation in the magnetic field.

  13. Flow and flow-induced vibration of a square array of cylinders in steady currents

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Ming [School of Computing, Engineering and Mathematics, University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751 (Australia); Cheng, Liang; An, Hongwei; Tong, Feifei, E-mail: m.zhao@uws.edu.au [School of Civil, Environmental and Mining Engineering, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia)

    2015-08-15

    Flow and flow-induced vibration of a square array of cylinders are investigated by two-dimensional numerical simulations. Flow past 36 cylinders in an inline arranged square array and 33 cylinders in a staggered arranged square array is firstly simulated, for Re = 100 and the spacing ratios of L/D = 1.5, 2, 3, 4, 5. Only one vortex street is observed in the wake of the cylinder array when the spacing ratio is 1.5 in the inline arrangement and 1.5 and 2 in the staggered arrangement, indicating that the critical spacing ratio for the single-vortex street mode in the staggered arrangement is higher than that in the inline arrangement. The vortex shedding from the cylinders is suppressed at L/D = 3 for both inline and staggered arrangements. Vortex shedding from each individual cylinder is observed when L/D = 4. Flow-induced vibration of 36 cylinders in an inline square arrangement is studied for a constant Reynolds number of 100, two spacing ratios of 2 and 5, a constant mass ratio of 2.5 and a wide range of reduced velocities. It is found that for a spacing ratio of 2, the vibration of the cylinders in the four downstream columns does not start until the reduced velocity exceeds 4.5. The vibration of the cylinders progresses downstream with increasing reduced velocity. For a spacing ratio of 5, the vibrations of the cylinders in the most upstream column are similar to that of a single cylinder. The vibration amplitudes of the downstream cylinders peak at higher reduced velocities than that of a single cylinder. The maximum possible response amplitudes occur at the most downstream cylinders. (paper)

  14. Wind-induced vibration of single-layer reticulated shell structures

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jian-sheng; WU Yue; SHEN Shi-zhao

    2008-01-01

    Aiming at the dynamic response of reticulated shell structures under wind load, systematic parameter analyses on wind-induced responses of Kiewitt6-6 type single-layer spherical reticulated shell structures and three-way grid single-layer cylindrical reticulated shell structures were performed with the random simulation method in time domain, including geometric parameters, structural parameters and aerodynamic parameters. Moreover, a wind-induced vibration coefficient was obtained, which can be a reference to the wind-resistance design of reticulated shell structures. The results indicate that the geometric parameters are the most important factor influencing wind-induced responses of the reticulated shell structures; the wind-induced vibration coeffi-cient is 3.0 - 3.2 for the spherical reticulated shell structures and that is 2.8 - 3.0 for the cylindrical reticula-ted shell structures, which shows that the wind-induced vibration coefficients of these two kinds of space frames are well-proportioned.

  15. FIVPET Flow-Induced Vibration Test Report (1) - Candidate Spacer Grid Type I (Optimized H Type)

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kang Hee; Kang, Heung Seok; Yoon, Kyung Ho; Song, Kee Nam; Kim, Jae Yong

    2006-03-15

    The flow-induced vibration (FIV) test using a 5x5 partial fuel assembly was performed to evaluate mechanical/structural performance of the candidate spacer grid type I (Optimized H shape). From the measured vibration response of the test bundle and the flow parameters, design features of the spacer strap can be analyzed in the point of vibration and hydraulic aspect, and also compared with other spacer strap in simple comparative manner. Furthermore, the FIV test will contributes to understand behaviors of nuclear fuel in operating reactor. The FIV test results will be used to verify the theoretical model of fuel rod and assembly vibration. The aim of this report is to present the results of the FIV test of partial fuel assembly and to introduce the detailed test methodology and analysis procedure. In chapter 2, the overall configuration of test bundle and instrumented tube is remarked and chapter 3 will introduce the test facility (FIVPET) and test section. Chapter 4 deals with overall test condition and procedure, measurement and data acquisition devices, instrumentation equipment and calibration, and error analysis. Finally, test result of vibration and pressure fluctuation is presented and discussed in chapter 5.

  16. Shear flow induced vibrations of long slender cylinders with a wake oscillator model

    Institute of Scientific and Technical Information of China (English)

    Fei Ge; Wei Lu; Lei Wang; You-Shi Hong

    2011-01-01

    A time domain model is presented to study the vibrations of long slender cylinders placed in shear flow. Long slender cylinders such as risers and tension legs are widely used in the field of ocean engineering. They are subjected to vortex-induced vibrations (VIV) when placed within a transverse incident flow. A three dimensional model coupled with wake oscillators is formulated to describe the response of the slender cylinder in cross-flow and in-line directions.The wake oscillators are distributed along the cylinder and the vortex-shedding frequency is derived from the local current velocity. A non-linear fluid force model is accounted for the coupled effect between cross-flow and in-line vibrations. The comparisons with the published experimental data show that the dynamic features of VIV of long slender cylinder placed in shear flow can be obtained by the proposed model, such as the spanwise average displacement, vibration frequency, dominant mode and the combination of standing and traveling waves. The simulation in a uniform flow is also conducted and the result is compared with the case of nonuniform flow. It is concluded that the flow shear characteristic has significantly changed the cylinder vibration behavior.

  17. Importance of Added Mass and Damping in Flow-Induced Vibration Analysis of Tubes Bundle: An Overview

    Directory of Open Access Journals (Sweden)

    Faisal Karim Shami

    2012-01-01

    Full Text Available Flow-induced vibration is of prime concern to the designers of heat exchangers subjected to high flows of gases or liquids. Excessive vibration may cause tube failure due to fatigue or fretting-wear. Tube failure results in, expensive plant upholding and suffers loss of production. Therefore, tube failure due to unwarranted vibration must be avoided in process heat exchangers and nuclear steam generators, preferably at design stage. Such vibration problems may be avoided through a comprehensive flowinduced vibration analysis before fabrication of heat exchangers. However, it requires an understanding of vibration mechanism and parameters related to flow-induced vibration. For an accurate vibration analysis, it is of prime importance to have good estimates of structural and flow related dynamic parameters. Thus dynamic parameters such as added mass and damping are of significant concern in a flow regime. The purpose of this paper is to provide an overview of our state of knowledge and role of dynamic parameters in flow-induced vibration on tube bundles due to current trend of larger heat exchangers. The present paper provides published data, analysis, evaluation, formulation, and experimental studies related to hydrodynamic mass and damping by a large number of researchers. Guidelines for experimental research and heat exchangers design related to added mass and damping mechanisms subjected to both single and two-phase flow are outlined in this paper.

  18. The Tibetan singing bowl : an acoustics and fluid dynamics investigation

    CERN Document Server

    Terwagne, Denis

    2011-01-01

    We present the results of an experimental investigation of the acoustics and fluid dynamics of Tibetan singing bowls. Their acoustic behavior is rationalized in terms of the related dynamics of standing bells and wine glasses. Striking or rubbing a fluid-filled bowl excites wall vibrations, and concomitant waves at the fluid surface. Acoustic excitation of the bowl's natural vibrational modes allows for a controlled study in which the evolution of the surface waves with increasing forcing amplitude is detailed. Particular attention is given to rationalizing the observed criteria for the onset of edge-induced Faraday waves and droplet generation via surface fracture. Our study indicates that drops may be levitated on the fluid surface, induced to bounce on or skip across the vibrating fluid surface.

  19. Current-induced runaway vibrations in dehydrogenated graphene nanoribbons

    DEFF Research Database (Denmark)

    Christensen, Rasmus Bjerregaard; Lu, Jing Tao; Hedegard, Per

    2016-01-01

    We employ a semi-classical Langevin approach to study current-induced atomic dynamics in a partially dehydrogenated armchair graphene nanoribbon. All parameters are obtained from density functional theory. The dehydrogenated carbon dimers behave as effective impurities, whose motion decouples from...

  20. Using Fast Vibrations to Quench Friction-induced Oscillations

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel

    1999-01-01

    This work examines how friction-induced self-excited oscillations are affected by high-frequency ex-ternal excitation. Simple analytical approximations are derived for predicting the occurence of self-excited oscillations for the traditional mass-on-moving-belt model – with and without high-frequ...

  1. Development of Design Criteria for Fluid Induced Structural Vibration in Steam Generators and Heat Exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Catton, Ivan; Dhir, Vijay K.; Alquaddoomi, O.S.; Mitra, Deepanjan; Adinolfi, Pierangelo

    2004-03-26

    OAK-B135 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. In the nuclear industry, steam generators are often affected by this problem. However, flow-induced vibration is not limited to nuclear power plants, but to any type of heat exchanger used in many industrial applications such as chemical processing, refrigeration and air conditioning. Specifically, shell and tube type heat exchangers experience flow-induced vibration due to the high velocity flow over the tube banks. Flow-induced vibration in these heat exchangers leads to equipment breakdown and hence expensive repair and process shutdown. The goal of this research is to provide accurate measurements that can help modelers to validate their models using the measured experimental parameters and thereby develop better design criteria for avoiding fluid-elastic instability in heat exchangers. The research is divided between two primary experimental efforts, the first conducted using water alone (single phase) and the second using a mixture of air or steam and water as the working fluid (two phase). The outline of this report is as follows: After the introduction to fluid-elastic instability, the experimental apparatus constructed to conduct the experiments is described in Chapter 2 along with the measurement procedures. Chapter 3 presents results obtained on the tube array and the flow loop, as well as techniques used in data processing. The project performance is described and evaluated in Chapter 4 followed by

  2. Simulation of cross-flow-induced vibration of tube bundle by surface vorticity method

    Institute of Scientific and Technical Information of China (English)

    Fenghao WANG; Gedong JIANG; Jong Zhang Lin

    2008-01-01

    A fluid-structure interaction model based on Surface Vorticity Method (SVM) was used to study flow-induced vibrations of tube bundles in medium space ratio. The flow-induced vibrations of four tubes in a rotated square and a staggered tube bundle in three-row and five-column arrangements were simulated in the high sub-critical Reynolds number (Re) range. The results on fluid forces, tube responses and vorticity maps were pre-sented. The vorticity maps of the four rotated-square tubes changed dramatically when the rigid tubes were replaced by the flexible tubes. From the vorticity maps and vibration responses of the staggered tube bundle of different structural parameters, it was found that with the decrease of tube natural frequency, the maximal vibration response moved from the third row to the first. The results also showed that when more flexible tubes are used, the flow pattern changed drastically and the fluid-structure interaction imposed a dominant impact on the flow.

  3. Wind-induced vibration control of bridges using liquid column damper

    Institute of Scientific and Technical Information of China (English)

    薛素铎; 高赞明; 徐幼麟

    2002-01-01

    The potential application of tuned liquid column damper (TLCD) for suppressing wind-induced vibration of long span bridges is explored in this paper. By installing the TLCD in the bridge deck, a mathematical model for the bridge-TLCD system is established. The governing equations of the system are developed by considering all three displacement components of thc deck in vertical, lateral, and torsional vibrations, in which the interactions between the bridge deck, the TLCD, the aeroelastic forces, and the aerodynamic forces are fully reflected. Both buffeting and flutter analyses are carried out. The buffeting analysis is performed through random vibration approach, and a critical flutter condition is identified from flutter analysis. A numerical example is presented to demonstrate the control effectiveness of the damper and it is shown that the TLCD can be an effective device for suppressing wind-induced vibration of long span bridges, either for reducing the buffeting response or increasing the critical flutter wind velocity of the bridge.

  4. Flow-induced vibration testing of replacement thermowell designs

    Science.gov (United States)

    Haslinger, K. H.

    2003-09-01

    Inconel 600 Primary Water Stress Corrosion Cracking (PWSCC) in Nuclear Pressurized Water Reactors (PWRs) has necessitated the repair/replacement of various small bore nozzles. These repairs/replacements must be designed to avoid unwanted vibrations. So, to this end, new RTD-Thermowell-Nozzle replacement designs were developed and subjected to flow testing over a velocity range from 9.14 to 33.53m/s (30-110ft/s), and temperatures ranging from 121°C to 316°C (250-600°F). The replacement nozzles are welded on the pipe OD, rather than on the pipe ID. A split, tapered ferrule is used to support the nozzle tip inside the pipe bore. This maintains high thermowell tip-resonance frequencies with the objective of avoiding self-excitation from vortex shedding that is believed to have caused failures in an earlier design during initial, precritical plant startup testing. The flow testing was complicated by the small size of the thermowell tips (5.08mm or 0.2in ID), which necessitated use of a complement of low temperature and high temperature instrumentation. Since the high temperature device had an internal resonance (750Hz) within the frequency range of interest (0-2500Hz), adequate sensor correlations had to be derived from low temperature tests. The current nozzle/thermowell design was tested concurrently with two slight variations of the replacement design. The acceleration signals were acquired during incremental and continuous flow sweeps, nominally at 5kHz sampling rates and for time domain processing as high as 25kHz. Whereas vortex-shedding frequencies were predicted to prevail between 400 and 1500Hz, no such response was observed at these frequencies. Rather, the thermowell tips responded due to turbulent buffeting with a peak response that was related directly to flow velocity. Lift direction response was always larger than drag direction response. The thermowell tips also responded at their natural tip frequencies in a narrow band random fashion. At the higher

  5. Detection of explosive events by monitoring acoustically-induced geomagnetic perturbations

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, J P; Rock, D R; Shaeffer, D L; Warshaw, S I

    1999-10-07

    The Black Thunder Coal Mine (BTCM) near Gillette, Wyoming was used as a test bed to determine the feasibility of detecting explosion-induced geomagnetic disturbances with ground-based induction magnetometers. Two magnetic observatories were fielded at distances of 50 km and 64 km geomagnetically north from the northernmost edge of BTCM. Each observatory consisted of three separate but mutually orthogonal magnetometers, Global Positioning System (GPS) timing, battery and solar power, a data acquisition and storage system, and a three-axis seismometer. Explosions with yields of 1 to 3 kT of TNT equivalent occur approximately every three weeks at BTCM. We hypothesize that explosion-induced acoustic waves propagate upward and interact collisionally with the ionosphere to produce ionospheric electron density (and concomitant current density) perturbations which act as sources for geomagnetic disturbances. These disturbances propagate through an ionospheric Alfven waveguide that we postulate to be leaky (due to the imperfectly conducting lower ionospheric boundary). Consequently, wave energy may be observed on the ground. We observed transient pulses, known as Q-bursts, with pulse widths about 0.5 s and with spectral energy dominated by the Schumann resonances. These resonances appear to be excited in the earth-ionosphere cavity by Alfven solitons that may have been generated by the explosion-induced acoustic waves reaching the ionospheric E and F regions and that subsequently propagate down through the ionosphere to the atmosphere. In addition, we observe late time (> 800 s) ultra low frequency (ULF) geomagnetic perturbations that appear to originate in the upper F region ({approximately}300 km) and appear to be caused by the explosion-induced acoustic wave interacting with that part of the ionosphere. We suggest that explosion-induced Q-bursts may be discriminated from naturally occurring Q-bursts by association of the former with the late time explosion-induced ULF

  6. Numerical investigation of piled raft foundation in mitigating embankment vibrations induced by high-speed trains

    Institute of Scientific and Technical Information of China (English)

    付强; 刘汉龙; 丁选明; 郑长杰

    2015-01-01

    A three-dimensional dynamic finite element model of track-ballast-embankment and piled raft foundation system is established. Dynamic response of a railway embankment to a high-speed train is simulated for two cases: soft ground improved by piled raft foundation, and untreated soft ground. The obtained results are compared both in time domain and frequency domain to evaluate the effectiveness of the ground improvement in mitigating the embankment vibrations induced by high-speed trains. The results show that ground improving methods can significantly reduce the embankment vibrations at all considered train speeds(36-432 km/h). The ground response to a moving load is dictated largely by the relationship between load speed and characteristic value of wave velocities of the ground medium. At low speeds, the ground response from a moving load is essentially quasi-static. That is, the displacements fields are essential the static fields under the load simply moving with it. For the soft ground, the displacement on the ballast surface is large at all observed train speeds. For the model case where the ground is improved by piled raft foundation, the peak displacement is reduced at all considered train speeds compared with the case without ground improvement. Based on the effect of energy-dissipating of ballast-embankment-ground system with damping, the train-induced vibration waves moving in ballast and embankment are trapped and dissipated, and thus the vibration amplitudes of dynamic displacement outside the embankment are significantly reduced. But for the vibration amplitude of dynamic velocity, the vibration waves in embankment are absorbed or reflected back, and the velocity amplitudes at the ballast and embankment surface are enhanced. For the change of the vibration character of embankment and ballast, the bearing capacity and dynamic character are improved. Therefore, both of the static and dynamic displacements are reduced by ground improvement; the dynamic

  7. Numerical investigation of piled raft foundation in mitigating embankment vibrations induced by high-speed trains

    Institute of Scientific and Technical Information of China (English)

    付强; 刘汉龙; 丁选明; 郑长杰

    2015-01-01

    A three-dimensional dynamic finite element model of track-ballast-embankment and piled raft foundation system is established. Dynamic response of a railway embankment to a high-speed train is simulated for two cases: soft ground improved by piled raft foundation, and untreated soft ground. The obtained results are compared both in time domain and frequency domain to evaluate the effectiveness of the ground improvement in mitigating the embankment vibrations induced by high-speed trains. The results show that ground improving methods can significantly reduce the embankment vibrations at all considered train speeds (36− 432 km/h). The ground response to a moving load is dictated largely by the relationship between load speed and characteristic value of wave velocities of the ground medium. At low speeds, the ground response from a moving load is essentially quasi-static. That is, the displacements fields are essential the static fields under the load simply moving with it. For the soft ground, the displacement on the ballast surface is large at all observed train speeds. For the model case where the ground is improved by piled raft foundation, the peak displacement is reduced at all considered train speeds compared with the case without ground improvement. Based on the effect of energy-dissipating of ballast-embankment-ground system with damping, the train-induced vibration waves moving in ballast and embankment are trapped and dissipated, and thus the vibration amplitudes of dynamic displacement outside the embankment are significantly reduced. But for the vibration amplitude of dynamic velocity, the vibration waves in embankment are absorbed or reflected back, and the velocity amplitudes at the ballast and embankment surface are enhanced. For the change of the vibration character of embankment and ballast, the bearing capacity and dynamic character are improved. Therefore, both of the static and dynamic displacements are reduced by ground improvement; the dynamic

  8. A scaling procedure for panel vibro-acoustic response induced by turbulent boundary layer

    Science.gov (United States)

    Xiaojian, Zhao; Bangcheng, AI; Ziqiang, Liu; Dun, Li

    2016-10-01

    A new method of predicting structure vibration based on scaled model is proposed for panel vibration induced by turbulent boundary layer. The aerodynamic effects such as the variation of TBL excitation and its frequency for a scaled model used, and the material properties are also considered in the proposed scaling law. The contributions of resonant modes dominate the energy of low-frequency vibration, and the scaling procedure is derived with the analytical expansion method. For high-frequency vibration, the SEA method is used to derive the scaling law because of the highly coupled modes in the frequency range of analysis. A criterion is also proposed to identify the boundary between high-frequency and low-frequency vibration. For the validation of the proposed scaling procedure, an experiment is conducted with scaled plate models under external excitation. Despite slightly offset of resonant frequencies in the low frequency range likely caused by the difference in the condition of panel fixing, the results reveal that the proposed scaling procedure is effective.

  9. Suppression of wind-induced vibrations of a seesaw-type oscillator by means of a dynamic absorber

    NARCIS (Netherlands)

    Lumbantobing, H.

    2003-01-01

    In this paper the suppression of wind-induced vibrations of a seesaw-type oscillator by means of a dynamic absorber is considered. With suppression the shift of the critical flow velocity to higher values as well as the reduction of vibration amplitudes is meant. The equations of motion are derived

  10. Soft Computing Approach to Evaluate and Predict Blast-Induced Ground Vibration

    Science.gov (United States)

    Khandelwal, Manoj

    2010-05-01

    Drilling and blasting is still one of the major economical operations to excavate a rock mass. The consumption of explosive has been increased many folds in recent years. These explosives are mainly used for the exploitation of minerals in mining industry or the removal of undesirable rockmass for community development. The amount of chemical energy converted into mechanical energy to fragment and displace the rockmass is minimal. Only 20 to 30% of this explosive energy is utilized for the actual fragmentation and displacement of rockmass and rest of the energy is wasted in undesirable ill effects, like, ground vibration, air over pressure, fly rock, back break, noise, etc. Ground vibration induced due to blasting is very crucial and critical as compared to other ill effects due to involvement of public residing in the close vicinity of mining sites, regulating and ground vibration standards setting agencies together with mine owners and environmentalists and ecologists. Also, with the emphasis shifting towards eco-friendly, sustainable and geo-environmental activities, the field of ground vibration have now become an important and imperative parameter for safe and smooth running of any mining and civil project. The ground vibration is a wave motion, spreading outward from the blast like ripples spreading outwards due to impact of a stone dropped into a pond of water. As the vibration passes through the surface structures, it induces vibrations in those structures also. Sometimes, due to high ground vibration level, dwellings may get damaged and there is always confrontation between mine management and the people residing in the surroundings of the mine area. There is number of vibration predictors available suggested by different researchers. All the predictors estimate the PPV based on mainly two parameters (maximum charge used per delay and distance between blast face to monitoring point). However, few predictors considered attenuation/damping factor too. For

  11. Natural and laser-induced cavitation in corn stems: On the mechanisms of acoustic emissions

    Directory of Open Access Journals (Sweden)

    Gabriel Mario Bilmes

    2012-05-01

    Full Text Available Water in plant xylem is often superheated, and therefore in a meta-stable state. Under certain conditions, it may suddenly turn from the liquid to the vapor state. This cavitation process produces acoustic emissions. We report the measurement of ultrasonic acoustic emissions (UAE produced by natural and induced cavitation in corn stems. We induced cavitation and UAE in vivo, in well controlled and reproducible experiments, by irradiating the bare stem of the plants with a continuous-wave laser beam. By tracing the source of UAE, we were able to detect absorption and frequency filtering of the UAE propagating through the stem. This technique allows the unique possibility of studying localized embolism of plant conduits, and thus to test hypotheses on the hydraulic architecture of plants. Based on our results, we postulate that the source of UAE is a transient "cavity oscillation"' triggered by the disruptive effect of cavitation inception.

  12. The effect of temperature dependent tissue parameters on acoustic radiation force induced displacements

    CERN Document Server

    Suomi, Visa; Konofagou, Elisa; Cleveland, Robin

    2016-01-01

    Multiple ultrasound elastography techniques rely on acoustic radiation force (ARF) in monitoring high-intensity focused ultrasound (HIFU) therapy. However, ARF is dependent on tissue attenuation and sound speed, both of which are also known to change with temperature making the therapy monitoring more challenging. Furthermore, the viscoelastic properties of tissue are also temperature dependent, which affects the displacements induced by ARF. The aim of this study is to quantify the temperature dependent changes in the acoustic and viscoelastic properties of liver and investigate their effect on ARF induced displacements by using both experimental methods and simulations. Furthermore, the temperature dependent viscoelastic properties of liver are experimentally measured over a frequency range of 0.1-200 Hz at temperatures reaching 80 C, and both conventional and fractional Zener models are used to fit the data. The fractional Zener model was found to fit better with the experimental viscoelasticity data with ...

  13. Natural and laser-induced cavitation in corn stems: On the mechanisms of acoustic emissions

    CERN Document Server

    Fernández, E; Bilmes, G M; 10.4279/PIP.040003

    2012-01-01

    Water in plant xylem is often superheated, and therefore in a meta-stable state. Under certain conditions, it may suddenly turn from the liquid to the vapor state. This cavitation process produces acoustic emissions. We report the measurement of ultrasonic acoustic emissions (UAE) produced by natural and induced cavitation in corn stems. We induced cavitation and UAE in vivo, in well controlled and reproducible experiments, by irradiating the bare stem of the plants with a continuous-wave laser beam. By tracing the source of UAE, we were able to detect absorption and frequency filtering of the UAE propagating through the stem. This technique allows the unique possibility of studying localized embolism of plant conduits, and thus to test hypotheses on the hydraulic architecture of plants. Based on our results, we postulate that the source of UAE is a transient "cavity oscillation" triggered by the disruptive effect of cavitation inception.

  14. Acute exposure to vibration is an apoptosis-inducing stimulus in the vocal fold epithelium.

    Science.gov (United States)

    Novaleski, Carolyn K; Kimball, Emily E; Mizuta, Masanobu; Rousseau, Bernard

    2016-10-01

    Clinical voice disorders pose significant communication-related challenges to patients. The purpose of this study was to quantify the rate of apoptosis and tumor necrosis factor-alpha (TNF-α) signaling in vocal fold epithelial cells in response to increasing time-doses and cycle-doses of vibration. 20 New Zealand white breeder rabbits were randomized to three groups of time-doses of vibration exposure (30, 60, 120min) or a control group (120min of vocal fold adduction and abduction). Estimated cycle-doses of vocal fold vibration were extrapolated based on mean fundamental frequency. Laryngeal tissue specimens were evaluated for apoptosis and gene transcript and protein levels of TNF-α. Results revealed that terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining was significantly higher after 120min of vibration compared to the control. Transmission electron microscopy (TEM) revealed no significant effect of time-dose on the mean area of epithelial cell nuclei. Extrapolated cycle-doses of vibration exposure were closely related to experimental time-dose conditions, although no significant correlations were observed with TUNEL staining or mean area of epithelial cell nuclei. TUNEL staining was positively correlated with TNF-α protein expression. Our findings suggest that apoptosis can be induced in the vocal fold epithelium after 120min of modal intensity phonation. In contrast, shorter durations of vibration exposure do not result in apoptosis signaling. However, morphological features of apoptosis are not observed using TEM. Future studies are necessary to examine the contribution of abnormal apoptosis to vocal fold diseases.

  15. Wire-bond failures induced by resonant vibrations in the CDF silicon detector

    Energy Technology Data Exchange (ETDEWEB)

    Bolla, G. E-mail: bolla@fnal.gov; Atac, M.; Pavlicek, V.; Nahn, S.; Garcia-Sciveres, M.; Mumford, R.; Nguyen, T.; Forrester, S.; Hill, C.; Olszewski, J.; Rahaman, A.; Goldstein, J.; Ashmanskas, B.; Maruyama, T.; Zimmerman, T.; Moccia, S.; Lewis, J

    2004-02-01

    Unrecoverable internal failures of modules in the CDF Run2 Silicon detector have been observed since its installation in early 2001. A fraction of these failures has been categorized as infant mortality. Other failures occurring later were strongly correlated with fixed trigger conditions. These failures are explained by wire-bonds breaking due to fatigue stress induced by resonant vibration. These resonant vibrations are a direct consequence of the oscillating Lorentz forces induced by the 1.4 T magnetic field on wire-bonds carrying non-DC current. Changes have been implemented in data-taking procedures in order to minimize the occurrences of such failures and to prolong the lifetime of the detector itself. A more general analysis of the topic has been pursued. Changes in the packaging and assembly processes for future applications have been investigated.

  16. Model Test Study on Ice Induced Vibration of A Compliant Conical Structure

    Institute of Scientific and Technical Information of China (English)

    HUNAG Yan; SHI Qing-zeng; SONG An

    2005-01-01

    The problem of ice induced vibration is common to ocean engineering of cold region countries. To study the ice induced vibration of a compliant conical structure, a series of model tests have been performed and some breakthrough progresses made. The ice sheet before the compliant conical structure is found to fail by two-time breaking in the tests. The process of two-time breaking behaves in two modes, and the general control of the ice and structural conditions determine the mode in which the ice force would behave. Two dynamic ice force functions are established respectively for the two modes of two-time breaking process in this paper. The numerical simulation results are in good agreement with the measured results, indicating that the dynamic ice force functions given in this paper can fully reflect the real situation of the dynamic ice force on a compliant conical structure.

  17. NUMERICAL PREDICTION OF FATIGUE DAMAGE IN STEEL CATENARY RISER DUE TO VORTEX-INDUCED VIBRATION

    Institute of Scientific and Technical Information of China (English)

    GAO Yun; ZONG Zhi; SUN Lei

    2011-01-01

    For studying the characteristics of Steel Catenary Riser (SCR), a simplified pinned-pinned cable model of vibration is established. The natural frequencies, the normalized mode shapes and mode curvatures of the SCR are calculated. The fatigue damage of the SCR can be obtained by applying the modal superposition method combined with the parameters of S - N curve.For analyzing the relation between the current velocity and the SCR's fatigue damage induced by the vortex-induced vibration, ten different current states are evaluated. Then, some useful conclusions are drawn, especially an important phenomenon is revealed that the maximum fatigue damage in the riser usually occurs near the area of the boundary ends.

  18. Hybrid predictions of railway induced ground vibration using a combination of experimental measurements and numerical modelling

    Science.gov (United States)

    Kuo, K. A.; Verbraken, H.; Degrande, G.; Lombaert, G.

    2016-07-01

    Along with the rapid expansion of urban rail networks comes the need for accurate predictions of railway induced vibration levels at grade and in buildings. Current computational methods for making predictions of railway induced ground vibration rely on simplifying modelling assumptions and require detailed parameter inputs, which lead to high levels of uncertainty. It is possible to mitigate against these issues using a combination of field measurements and state-of-the-art numerical methods, known as a hybrid model. In this paper, two hybrid models are developed, based on the use of separate source and propagation terms that are quantified using in situ measurements or modelling results. These models are implemented using term definitions proposed by the Federal Railroad Administration and assessed using the specific illustration of a surface railway. It is shown that the limitations of numerical and empirical methods can be addressed in a hybrid procedure without compromising prediction accuracy.

  19. Prediction of Streamwise Flow-Induced Vibration of A Circular Cylinder in the First Instability Range

    Institute of Scientific and Technical Information of China (English)

    Xu Wan-hai; Yu Jian-xing; Du Jie; CHENG An-kang; KANG Hao

    2012-01-01

    The streamwise flow-induced vibration of a circular cylinder with symmetric vortex shedding in the first instability range is investigated,and a wake oscillator model for the dynamic response prediction is proposed.An approach is applied to calibrate the empirical parameters in the present model; the numerical and experimental results are compared to validate the proposed model.It can be found that the present prediction model is accurate and sufficiently simple to be easily applied in practice.

  20. Rain-Wind Induced Vibration Mitigation of Stay Cables by Aerodynamic Means

    Institute of Scientific and Technical Information of China (English)

    ZHAO Jun; LI Ming-shui; LIAO Hai-li

    2009-01-01

    Stay cables with various surface profiles were tested in wind tunnel.Dimples and helical fillets were applied to mitigate the rain-wind induced vibration.The rain-wind excited responses of the cable with smooth surface were larger than those of the cables with dimples and helical fillets.At high Reynolds number,the drag coefficients of cables with dimples and helical fillets are much larger than those of smooth surface cable.

  1. Water hammer, flow induced vibration and safety/relief valve loads

    Energy Technology Data Exchange (ETDEWEB)

    Valandani, P.; Uffer, R.; Sexton, D.

    1984-09-01

    This report presents the results of an evaluation performed to determine current and recommended practices regarding the consideration of water hammer, flow-induced vibration and safety-relief valve loads in the design of nuclear power plant piping systems. Current practices were determined by a survey of industry experts. Recommended practices were determined by evaluating factors such as load magnitude and frequency content, system susceptibility to load occurrence and safety effects of postulated piping damage.

  2. On vortex shedding and prediction of vortex-induced vibrations of circular cylinders

    Energy Technology Data Exchange (ETDEWEB)

    Halse, Karl Henning

    1997-12-31

    In offshore installations, many crucial components can be classified as slender marine structures: risers, mooring lines, umbilicals and cables, pipelines. This thesis studies the vortex shedding phenomenon and the problem of predicting vortex-induced vibrations of such structures. As the development of hydrocarbons move to deeper waters, the importance of accurately predicting the vortex-induced response has increased and so the need for proper response prediction methods is large. This work presents an extensive review of existing research publications about vortex shedding from circular cylinders and the vortex-induced vibrations of cylinders and the different numerical approaches to modelling the fluid flow. The response predictions from different methods are found to disagree, both in response shapes and in vibration amplitudes. This work presents a prediction method that uses a fully three-dimensional structural finite element model integrated with a laminar two-dimensional Navier-Stokes solution modelling the fluid flow. This solution is used to study the flow both around a fixed cylinder and in a flexibly mounted one-degree-of-freedom system. It is found that the vortex-shedding process (in the low Reynolds number regime) is well described by the computer program, and that the vortex-induced vibration of the flexibly mounted section do reflect the typical dynamic characteristics of lock-in oscillations. However, the exact behaviour of the experimental results found in the literature was not reproduced. The response of the three-dimensional structural model is larger than the expected difference between a mode shape and a flexibly mounted section. This is due to the use of independent hydrodynamic sections along the cylinder. The predicted response is not unrealistic, and the method is considered a powerful tool. 221 refs., 138 figs., 36 tabs.

  3. Non-linear system identification in flow-induced vibration

    Energy Technology Data Exchange (ETDEWEB)

    Spanos, P.D.; Zeldin, B.A. [Rice Univ., Houston, TX (United States); Lu, R. [Hudson Engineering Corp., Houston, TX (United States)

    1996-12-31

    The paper introduces a method of identification of non-linear systems encountered in marine engineering applications. The non-linearity is accounted for by a combination of linear subsystems and known zero-memory non-linear transformations; an equivalent linear multi-input-single-output (MISO) system is developed for the identification problem. The unknown transfer functions of the MISO system are identified by assembling a system of linear equations in the frequency domain. This system is solved by performing the Cholesky decomposition of a related matrix. It is shown that the proposed identification method can be interpreted as a {open_quotes}Gram-Schmidt{close_quotes} type of orthogonal decomposition of the input-output quantities of the equivalent MISO system. A numerical example involving the identification of unknown parameters of flow (ocean wave) induced forces on offshore structures elucidates the applicability of the proposed method.

  4. Vibration induced phase noise in Mach-Zehnder atom interferometers

    CERN Document Server

    Miffre, A; Büchner, M; Trénec, G; Vigué, J; Miffre, Alain; Jacquey, Marion; B\\"{u}chner, Matthias; Vigu\\'{e}, Jacques

    2006-01-01

    The high inertial sensitivity of atom interferometers has been used to build accelerometers and gyrometers but this sensitivity makes these interferometers very sensitive to the laboratory seismic noise. This seismic noise induces a phase noise which is large enough to reduce the fringe visibility in many cases. We develop here a model calculation of this phase noise in the case of Mach-Zehnder atom interferometers and we apply this model to our thermal lithium interferometer. We are thus able to explain the observed dependence of the fringe visibility with the diffraction order. The dynamical model developed in the present paper should be very useful to further reduce this phase noise in atom interferometers and this reduction should open the way to improved interferometers.

  5. Predictions and observations of global beta-induced Alfven-acoustic modes in JET and NSTX

    Energy Technology Data Exchange (ETDEWEB)

    Gorelenkov, N N [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Berk, H L [Institute for Fusion Studies, University of Texas, Austin, TX 78712 (United States); Crocker, N A [Institute of Plasma and Fusion Research, University of California, Los Angeles, CA 90095-1354 (United States); Fredrickson, E D [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Kaye, S [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Kubota, S [Institute of Plasma and Fusion Research, University of California, Los Angeles, CA 90095-1354 (United States); Park, H [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Peebles, W [Institute of Plasma and Fusion Research, University of California, Los Angeles, CA 90095-1354 (United States); Sabbagh, S A [Department of Applied Physics, Columbia University, New York, NY 10027-6902 (United States); Sharapov, S E [Euroatom/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom); Stutmat, D [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Tritz, K [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Levinton, F M [Nova Photonics, One Oak Place, Princeton, NJ 08540 (United States); Yuh, H [Nova Photonics, One Oak Place, Princeton, NJ 08540 (United States)

    2007-12-15

    In this paper we report on observations and interpretations of a new class of global MHD eigenmode solutions arising in gaps in the low frequency Alfven-acoustic continuum below the geodesic acoustic mode frequency. These modes have been just reported (Gorelenkov et al 2007 Phys. Lett. 370 70-7) where preliminary comparisons indicate qualitative agreement between theory and experiment. Here we show a more quantitative comparison emphasizing recent NSTX experiments on the observations of the global eigenmodes, referred to as beta-induced Alfven-acoustic eigenmodes (BAAEs), which exist near the extrema of the Alfven-acoustic continuum. In accordance to the linear dispersion relations, the frequency of these modes may shift as the safety factor, q, profile relaxes. We show that BAAEs can be responsible for observations in JET plasmas at relatively low beta <2% as well as in NSTX plasmas at relatively high beta >20%. In NSTX plasma observed magnetic activity has the same properties as predicted by theory for the mode structure and the frequency. Found numerically in NOVA simulations BAAEs are used to explain the observed properties of relatively low frequency experimental signals seen in NSTX and JET tokamaks.

  6. Tactile Perception and Friction-Induced Vibrations: Discrimination of Similarly Patterned Wood-Like Surfaces.

    Science.gov (United States)

    Dacleu Ndengue, Jessica; Cesini, B Ilaria; Faucheu, C Jenny; Chatelet, D Eric; Zahouani, E Hassan; Delafosse, F David; Massi, G Francesco

    2016-12-22

    The tactile perception of a surface texture is mediated by factors such as material, topography and vibrations induced by the sliding contact. In this paper, sensory characterizations are developed together with topographical and tribo-tactile characterizations to relate perceived features with objective measurements of tribological and dynamic signals. Two sets of surface samples are used in this study: the first set is made of a commercial floor covering tiles that aim at counter-typing natural wood flooring, with both a visual and a tactile texture mimicking wood. A second set is custom-made by replicating the first set using a plain purple polyurethane resin. The comparison between tribo-tactile signals and sensory analysis allowed the identification of objective indices for textures with slight topographical differences. Even though the topography of the replicated samples is the same as their corresponding commercial products, the fact that the material is different, induces differences in the contact and vibrational parameters. This in turn modifies the discrimination performances during the sensory experiment. Tactile characteristics collected during sensory procedures are found to be in agreement with objective indices such as friction coefficients and induced vibrations.

  7. Mitigation of Railway Traffic Induced Vibrations: The Influence of Barriers in Elastic Half-Space

    Directory of Open Access Journals (Sweden)

    Michele Buonsanti

    2009-01-01

    Full Text Available In this paper, the problem of vibrations induced by trains and their propagation through the soil is studied. Particular attention is focused on the vibration induced by trains in motion and on the effects of such vibrations on the foundations of buildings in proximity of the tracks. The interaction between propagating waves induced by trains in motion and buildings foundations is a problem which does not admit a straightforward analytical solution; thus a solution is given by the use of a model based on the finite elements method. Firstly, we analyze the theoretical aspects of the problem by considering constant or harmonic loads moving along a straight railway track; then, we define a transfer function soil-railway and the response function of the entire system. The study aims to address the wave propagation in an elastic semi-space and the presence in the ground of a discontinuity element, such as a barrier of a given depth is considered. The efficiency variation of barriers is analyzed in function of the different materials used, and different numerical simulations are analyzed in order to study how the wave propagation and the track-soil interaction are influenced by the membrane, seen as damping barrier.

  8. Acoustic trauma-induced auditory cortex enhancement and tinnitus

    Institute of Scientific and Technical Information of China (English)

    Erin Laundrie; Wei Sun

    2014-01-01

    There is growing evidence suggests that noise-induced cochlear damage may lead to hyperexcitability in the central auditory system (CAS) which may give rise to tinnitus. However, the correlation between the onset of the neurophysiological changes in the CAS and the onset of tinnitus has not been well studied. To investigate this relationship, chronic electrodes were implanted into the auditory cortex (AC) and sound evoked activities were measured from awake rats before and after noise exposure. The auditory brainstem response (ABR) was used to assess the degree of noise-induced hearing loss. Tinnitus was evaluated by measuring gap-induced prepulse inhibition (gap-PPI). Rats were exposed monaurally to a high-intensity narrowband noise centered at 12 kHz at a level of 120 dB SPL for 1 h. After the noise exposure, all the rats developed either permanent (>2 weeks) or temporary (<3 days) hearing loss in the exposed ear(s). The AC amplitudes increased significantly 4 h after the noise exposure. Most of the exposed rats also showed decreased gap-PPI. The post-exposure AC enhancement showed a positive correlation with the amount of hearing loss. The onset of tinnitus-like behavior was happened after the onset of AC enhancement.

  9. Vortex-induced vibrations of a flexible cylinder at large inclination angle.

    Science.gov (United States)

    Bourguet, Rémi; Triantafyllou, Michael S

    2015-01-28

    The free vibrations of a flexible circular cylinder inclined at 80° within a uniform current are investigated by means of direct numerical simulation, at Reynolds number 500 based on the body diameter and inflow velocity. In spite of the large inclination angle, the cylinder exhibits regular in-line and cross-flow vibrations excited by the flow through the lock-in mechanism, i.e. synchronization of body motion and vortex formation. A profound reconfiguration of the wake is observed compared with the stationary body case. The vortex-induced vibrations are found to occur under parallel, but also oblique vortex shedding where the spanwise wavenumbers of the wake and structural response coincide. The shedding angle and frequency increase with the spanwise wavenumber. The cylinder vibrations and fluid forces present a persistent spanwise asymmetry which relates to the asymmetry of the local current relative to the body axis, owing to its in-line bending. In particular, the asymmetrical trend of flow-body energy transfer results in a monotonic orientation of the structural waves. Clockwise and counter-clockwise figure eight orbits of the body alternate along the span, but the latter are found to be more favourable to structure excitation. Additional simulations at normal incidence highlight a dramatic deviation from the independence principle, which states that the system behaviour is essentially driven by the normal component of the inflow velocity.

  10. Influence of subglottic stenosis on the flow-induced vibration of a computational vocal fold model

    Science.gov (United States)

    Smith, Simeon L.; Thomson, Scott L.

    2013-04-01

    The effect of subglottic stenosis on vocal fold vibration is investigated. An idealized stenosis is defined, parameterized, and incorporated into a two-dimensional, fully coupled finite element model of the vocal folds and laryngeal airway. Flow-induced responses of the vocal fold model to varying severities of stenosis are compared. The model vibration was not appreciably affected by stenosis severities of up to 60% occlusion. Model vibration was altered by stenosis severities of 90% or greater, evidenced by decreased superior model displacement, glottal width amplitude, and flow rate amplitude. Predictions of vibration frequency and maximum flow declination rate were also altered by high stenosis severities. The observed changes became more pronounced with increasing stenosis severity and inlet pressure, and the trends correlated well with flow resistance calculations. Flow visualization was used to characterize subglottal flow patterns in the space between the stenosis and the vocal folds. Underlying mechanisms for the observed changes, possible implications for human voice production, and suggestions for future work are discussed.

  11. Vibrational wave packet induced oscillations in two-dimensional electronic spectra. II. Theory

    CERN Document Server

    Mancal, Tomas; Milota, Franz; Lukes, Vladimir; Kauffmann, Harald F; Sperling, Jaroslaw

    2010-01-01

    We present a theory of vibrational modulation of two-dimensional coherent Fourier transformed electronic spectra. Based on an expansion of the system's energy gap correlation function in terms of Huang-Rhys factors, we explain the time-dependent oscillatory behavior of the absorptive and dispersive parts of two-dimensional spectra of a two-level electronic system, weakly coupled to intramolecular vibrational modes. The theory predicts oscillations in the relative amplitudes of the rephasing and non-rephasing parts of the two-dimensional spectra, and enables to analyze time dependent two-dimensional spectra in terms of simple elementary components whose line-shapes are dictated by the interaction of the system with the solvent only. The theory is applicable to both low and high energy (with respect to solvent induced line broadening) vibrations. The results of this paper enable to qualitatively explain experimental observations on low energy vibrations presented in the preceding paper [A. Nemeth et al, arXiv:1...

  12. Flow-induced vibrations of long circular cylinders modeled by coupled nonlinear oscillators

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The dynamics of long slender cylinders undergoing vortex-induced vibrations (VIV) is studied in this work. Long slender cylinders such as risers or tension legs are widely used in the field of ocean engineering. When the sea current flows past a cylinder, it will be excited due to vortex shedding. A three-dimensional time domain model is formulated to describe the response of the cylinder, in which the in-line (IL) and cross-flow (CF) deflections are coupled. The wake dynamics, including in-line and cross-flow vibrations, is represented using a pair of non-linear oscillators distributed along the cylinder. The wake oscillators are coupled to the dynamics of the long cylinder with the acceleration coupling term. A non-linear fluid force model is accounted for to reflect the relative motion of cylinder to current. The model is validated against the published data from a tank experiment with the free span riser. The comparisons show that some aspects due to VIV of long flexible cylinders can be reproduced by the proposed model, such as vibrating frequency, dominant mode number, occurrence and transition of the standing or traveling waves. In the case study, the simulations show that the IL curvature is not smaller than CF curvature, which indicates that both IL and CF vibrations are important for the structural fatigue damage.

  13. A Patch Density Recommendation based on Convergence Studies for Vehicle Panel Vibration Response resulting from Excitation by a Diffuse Acoustic Field

    Science.gov (United States)

    Smith, Andrew; LaVerde, Bruce; Jones, Douglas; Towner, Robert; Waldon, James; Hunt, Ron

    2013-01-01

    Producing fluid structural interaction estimates of panel vibration from an applied pressure field excitation are quite dependent on the spatial correlation of the pressure field. There is a danger of either over estimating a low frequency response or under predicting broad band panel response in the more modally dense bands if the pressure field spatial correlation is not accounted for adequately. It is a useful practice to simulate the spatial correlation of the applied pressure field over a 2d surface using a matrix of small patch area regions on a finite element model (FEM). Use of a fitted function for the spatial correlation between patch centers can result in an error if the choice of patch density is not fine enough to represent the more continuous spatial correlation function throughout the intended frequency range of interest. Several patch density assumptions to approximate the fitted spatial correlation function are first evaluated using both qualitative and quantitative illustrations. The actual response of a typical vehicle panel system FEM is then examined in a convergence study where the patch density assumptions are varied over the same model. The convergence study results illustrate the impacts possible from a poor choice of patch density on the analytical response estimate. The fitted correlation function used in this study represents a diffuse acoustic field (DAF) excitation of the panel to produce vibration response.

  14. Vibro-acoustics

    CERN Document Server

    Nilsson, Anders

    2015-01-01

    This three-volume book gives a thorough and comprehensive presentation of vibration and acoustic theories. Different from traditional textbooks which typically deal with some aspects of either acoustic or vibration problems, it is unique of this book to combine those two correlated subjects together. Moreover, it provides fundamental analysis and mathematical descriptions for several crucial phenomena of Vibro-Acoustics which are quite useful in noise reduction, including how structures are excited, energy flows from an excitation point to a sound radiating surface, and finally how a structure radiates noise to a surrounding fluid. Many measurement results included in the text make the reading interesting and informative. Problems/questions are listed at the end of each chapter and the solutions are provided. This will help the readers to understand the topics of Vibro-Acoustics more deeply. The book should be of interest to anyone interested in sound and vibration, vehicle acoustics, ship acoustics and inter...

  15. Predictions of experimentally observed stochastic ground vibrations induced by blasting.

    Science.gov (United States)

    Kostić, Srđan; Perc, Matjaž; Vasović, Nebojša; Trajković, Slobodan

    2013-01-01

    In the present paper, we investigate the blast induced ground motion recorded at the limestone quarry "Suva Vrela" near Kosjerić, which is located in the western part of Serbia. We examine the recorded signals by means of surrogate data methods and a determinism test, in order to determine whether the recorded ground velocity is stochastic or deterministic in nature. Longitudinal, transversal and the vertical ground motion component are analyzed at three monitoring points that are located at different distances from the blasting source. The analysis reveals that the recordings belong to a class of stationary linear stochastic processes with Gaussian inputs, which could be distorted by a monotonic, instantaneous, time-independent nonlinear function. Low determinism factors obtained with the determinism test further confirm the stochastic nature of the recordings. Guided by the outcome of time series analysis, we propose an improved prediction model for the peak particle velocity based on a neural network. We show that, while conventional predictors fail to provide acceptable prediction accuracy, the neural network model with four main blast parameters as input, namely total charge, maximum charge per delay, distance from the blasting source to the measuring point, and hole depth, delivers significantly more accurate predictions that may be applicable on site. We also perform a sensitivity analysis, which reveals that the distance from the blasting source has the strongest influence on the final value of the peak particle velocity. This is in full agreement with previous observations and theory, thus additionally validating our methodology and main conclusions.

  16. Acoustic Imaging Frequency Dynamics of Ferroelectric Domains by Atomic Force Microscopy

    Institute of Scientific and Technical Information of China (English)

    ZHAO Kun-Yu; Shunji Takekawa; Kenji Kitamura; ZENG Hua-Rong; SONG Hong-Zhang; HUI Sen-Xing; LI Guo-Rong; YIN Qing-Rui; Kiyoshi Shimamura; Chinna Venkadasamy Kannan; Encarnacion Antonia Garcia Villora

    2008-01-01

    We report the acoustic imaging frequency dynamics of ferroelectric domains by low-frequency acoustic probe microscopy based on the commercial atomic force microscopy. It is found that ferroelectric domain could be firstly visualized at lower frequency down to 0.h kHz by AFM-based acoustic microscopy. The frequency-dependent acoustic signal revealed a strong acoustic response in the frequency range from 7 kHz to lO kHz, and reached maximum at 8.1 kHz. The acoustic contrast mechanism can be ascribed to the different elastic response of ferroelectric microstructures to local elastic stress fields, which is induced by the acoustic wave transmitting in the sample when the piezoelectric transducer is vibrating and exciting acoustic wave under ac electric fields due to normal piezoelectric effects.

  17. Advanced non-linear flow-induced vibration and fretting-wear analysis capabilities

    Energy Technology Data Exchange (ETDEWEB)

    Toorani, M.; Pan, L.; Li, R.; Idvorian, N. [Babcock and Wilcox Canada Ltd., Cambridge, Ontario (Canada); Vincent, B.

    2009-07-01

    Fretting wear is a potentially significant degradation mechanism in nuclear steam generators and other shell and tube heat transfer equipment as well. This paper presents an overview of the recently developed code FIVDYNA which is used for the non-linear flow-induced vibration and fretting wear analysis for operating steam generators (OTSG and RSG) and shell-and-tube heat exchangers. FIVDYNA is a non-linear time-history Flow-Induced Vibration (FIV) analysis computer program that has been developed by Babcock and Wilcox Canada to advance the understanding of tube vibration and tube to tube-support interaction. In addition to the dynamic fluid induced forces the program takes into account other tube static forces due to axial and lateral tube preload and thermal interaction loads. The program is capable of predicting the location where the fretting wear is most likely to occur and its magnitude taking into account the support geometry including gaps. FIVDYNA uses the general purpose finite element computer code ABAQUS as its solver. Using ABAQUS gives the user the flexibility to add additional forces to the tube ranging from tube preloads and the support offsets to thermal loads. The forces currently being modeled in FIVDYNA are the random turbulence, steady drag force, fluid-elastic forces, support offset and pre-strain force (axial loads). This program models the vibration of tubes and calculates the structural dynamic characteristics, and interaction forces between the tube and the tube supports. These interaction forces are then used to calculate the work rate at the support and eventually the predicted depth of wear scar on the tube. A very good agreement is found with experiments and also other computer codes. (author)

  18. Highly asymmetric interaction forces induced by acoustic waves in coupled plate structures

    CERN Document Server

    Fan, Xiying; Zhang, Shenwei; Ke, Manzhu; Liu, Zhengyou

    2015-01-01

    Mutual forces can be induced between coupled structures when illuminated by external acoustic waves. In this Letter, we propose a concept of asymmetric interaction between two coupled plate-like structures, which is generated by oppositely incident plane waves. Besides the striking contrast in magnitude, the mutual force induced by one of the incidences can be tuned extremely strong due to the resonant excitation of the flexural plate modes. The highly asymmetric interaction with enhanced strength in single side should be potentially useful, such as in designing ultrasound instruments and sensors.

  19. NUMERICAL ANALYSIS OF FLUID FLOW AND ADDED MASS INDUCED BY VIBRATION OF STRUCTURE

    Institute of Scientific and Technical Information of China (English)

    SU Li; LI Shu-juan; TANG Guo-an

    2005-01-01

    The fluid flow induced by light-density, low-stiffness structures was treated as inviscid, incompressible irrotational and steady plane flow. On the basis of the dipole configuration method, a singularity distribution method of distributing sources/sinks and dipoles on interfaces of the structure and fluid was developed to solve the problem of fluid flow induced by the vibration of common structures, such as columns and columns with fins,deduce the expression of kinetic energy of the fluid flow, and obtain the added mass finally.The calculational instances with analytical solutions prove the reliability of this method.

  20. Free and friction-induced in-plane vibration of annular disks

    Science.gov (United States)

    Tzou, Kevin Ihwa

    1998-12-01

    Vibration and noise from disk brakes negatively affect passenger comfort and perceptions of quality in both the automotive and aircraft industries. With regulatory pressure for stopping distance and the emphasis on smaller and lighter components, new brakes not only have to meet design and performance requirements, but must minimize vibration as well. Although materials and geometries vary from application to application, disk brakes generally consist of rotating annular disk(s) subjected to in-plane friction which dissipates the kinetic energy of the vehicle. During this process, friction-induced vibration of the disk(s) occurs, resulting in brake noise. Although sound radiation results from a disk's out-of-plane vibration, substantial in-plane motions must also be present due to the in-plane friction. This in-plane vibration can play a key role in the dynamics of the friction interface and hence, in brake noise and vibration. In this thesis, experimental and analytical methods are used to study the in-plane vibration of annular disks with a view toward understanding disk brake vibration. The issues that are addressed and the major findings include: (1) Characterization of in-plane modes in annular disks. For automotive rotors and thick annular disks, in-plane modes of vibration have frequencies that are both comparable to low-order bending modes and within the measured range for brake squeal. Despite the large in-plane friction force provided by disk brakes, no existing model includes in-plane disk motion with in-plane friction. A three-dimensional vibration model is used to determine frequencies and mode shapes for an annular disk subject to two boundary conditions: all surfaces traction-free, and all free except for a constrained inner edge. (2) Identification of frequency clusters. Using experimental and analytical methods, the frequencies for families of in-plane modes are found to converge to a common value with increasing disk thickness to the limit of the

  1. Mobile platform for acoustic mine detection applications

    Science.gov (United States)

    Libbey, Brad; Fenneman, Douglas; Burns, Brian

    2005-06-01

    Researchers in academia have successfully demonstrated acoustic landmine detection techniques. These typically employ acoustic or seismic sources to induce vibration in the mine/soil system, and use vibration sensors such as laser vibrometers or geophones to measure the resultant surface motion. These techniques exploit the unique mechanical properties of landmines to discriminate the vibration response of a buried mine from an off-target measurement. The Army requires the ability to rapidly and reliably scan an area for landmines and is developing a mobile platform at NVESD to meet this requirement. The platform represents an initial step toward the implementation of acoustic mine detection technology on a representative field vehicle. The effort relies heavily on the acoustic mine detection cart system developed by researchers at the University of Mississippi and Planning Systems, Inc. The NVESD platform consists of a John Deere E-gator configured with a robotic control system to accurately position the vehicle. In its present design, the E-gator has been outfitted with an array of laser vibrometers and a bank of loudspeakers. Care has been taken to ensure that the vehicle"s mounting hardware and data acquisition algorithms are sufficiently robust to accommodate the implementation of other sensor modalities. A thorough discussion of the mobile platform from its inception to its present configuration will be provided. Specific topics to be addressed include the vehicle"s control and data acquisition systems. Preliminary results from acoustic mine detection experiments will also be presented.

  2. Experimental verification of the asymtotic modal analysis method as applied to a rectangular acoustic cavity excited by structural vibration

    Science.gov (United States)

    Peretti, L. F.; Dowell, E. H.

    1992-01-01

    An experiment was performed on a rigid wall rectangular acoustic cavity driven by a flexible plate mounted in a quarter of one end wall and excited by white noise. The experiment was designed so that the assumptions of Asymptotic Modal Analysis (AMA) were satisfied for certain bandwidths and center frequencies. Measurements of sound pressure levels at points along the boundaries and incrementally into tbe interior were taken. These were compared with the theoretical results predicted with AMA, and found to be in good agreement, particularly for moderate (1/3 octave) bandwidths and sufficiently high center frequencies. Sound pressure level measurements were also taken well into the cavity interior at various points along the 5 totally rigid walls. The AMA theory, including boundary intensification effects, was shown to be accurate provided the assumption of large number of acoustic modes is satisfied, and variables such as power spectra of the wall acceleration, frequency, and damping are slowly varying in the frequency of bandwidth.

  3. Effect of Induced Vibration on the Blood Flow Properties in a Mechanical Aortic Valve

    Directory of Open Access Journals (Sweden)

    Kadhim Saleem Khalefa

    2014-07-01

    Full Text Available The effect of induced vibration on velocity distribution for the blood flow in the bileaflet mechanical heart valves conveying blood was investigated in this study. The bileaflet valve was simulated as an orifice. The induced vibration is due to the pulsed blood flow in the artery. Results presented in this study were performed using CFD FLUENT software. This analysis is based on the non-linear numerical solution by using a finite-element method, for the system of governing partial differential equations (continuity, momentum of Navier - Stokes equation of blood flow through the orifice. It has been found that as the flow through the orifice increased, the vibration at the orifice inlet increased. For steady state conditions, at Reynolds number 50 the recorded frequency was 20Hz. When the Reynolds number increased to 100 due to the increase in the blood flow the recorded frequency increased to 30Hz. The increase in frequency may result in damaging the blood red cells and platelets which subsequently results in increasing the blood clogging downstream of the orifice.

  4. Experimental Study on Vortex-Induced Vibrations of Submarine Pipeline near Seabed Boundary in Ocean Currents

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Unlike most previous studies on vortex-induced vibrations of a cylinder far from a boundary, this paper focuses on the influences of close proximity of a submarine pipeline to a rigid seabed boundary upon the dynamic responses of the pipeline in ocean currents. The effects of gap-to-diameter ratio and those of the stability parameter on the amplitude and frequency responses of a pipeline are investigated experimentally with a novel hydro-elastic facility. A comparison is made between the present experimental results of the amplitude and frequency responses for the pipes with seabed boundary effects and those for wall-free cylinders given by Govardhan and Williamson (2000) and Anand (1985). The comparison shows that the close proximity of a pipeline to seabed has much influence on the vortex-induced vibrations of the pipeline. Both the width of the lock-in ranges in terms of Vr and the dimensionless amplitude ratio Amax/D become larger with the decrease of the gap-to-diameter ratio e/D. Moreover, the vibration of the pipeline becomes easier to occur and its amplitude response becomes more intensive with the decrease of the stability parameter, while the pipeline frequency responses are affected slightly by the stability parameter.

  5. Analytical Model of Underground Train Induced Vibrations on Nearby Building Structures in Cameroon: Assessment and Prediction

    Directory of Open Access Journals (Sweden)

    Lezin Seba MINSILI

    2013-11-01

    Full Text Available The purpose of this research paper was to assess and predict the effect of vibrations induced by an underground railway on nearby-existing buildings prior to the construction of projected new railway lines of the National Railway Master Plan of Cameroon and after upgrading of the railway conceded to CAMRAIL linking the two most densely populated cities of Cameroon: Douala and Yaoundé. With the source-transmitter-receiver mathematical model as the train-soil-structure interaction model, taking into account sub-model parameters such as type of the train-railway system, typical geotechnical conditions of the ground and the sensitivity of the nearby buildings, the analysis is carried out over the entire system using the dynamic finite element method in the time domain. This subdivision of the model is a powerful tool that allows to consider different alternatives of sub-models with different characteristics, and thus to determine any critical excessive vibration impact. Based on semi-empirical analytical results obtained from presented models, the present work assesses and predicts characteristics of traffic-induced vibrations as a function of time duration, intensity and vehicle speed, as well as their influence on buildings at different levels.

  6. Analysis of blade vibration response induced by rotating stall in axial compressor

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    An experimental and numerical study was conducted to investigate the forced response of blade vibration induced by rotating stall in a low speed axial compressor.Measurements have been made of the transient stalling process in a low speed axial compressor stage.The CFD study was performed using solution of 3-dimensional Navier-Stokes equations,coupled with structure finite element models for the blades to identify modal shapes and structural deformations simultaneously.Interactions between fluid and structure were managed in a coupled manner,based on the interface information exchange until convergence in each time step.Based on the rotating stall measurement data obtained from a low speed axial compressor,the blade aeroelastic response induced by the rotating stall flow field was analyzed to study the vibration characteristics and the correlation between the phenomena.With this approach,good agreement between the numerical results and the experimental data was observed.The flow phenomena were well captured,and the results indicate that the rotating field stall plays a significant role in the blade vibration and stress affected by the flow excitation.

  7. Rapid phase change induced by double picosecond laser pulses and the dynamics of acoustic phonons

    Energy Technology Data Exchange (ETDEWEB)

    Li, Simian, E-mail: lism1972@qq.com [Hebei Key Laboratory of Optoelectronic Information and Geo-detection Technology, Shijiazhuang University of Economics, Shijiazhuang 050031 (China); State Key Laboratory of Optoelectronic Materials and Technology, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Liang, Guangfei [Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2013-12-02

    For a given phase change material and composition, the double laser pulses better than a single pulse for the crystallization process. We investigated the crystallization process in Si{sub 15}Sb{sub 85} thin films induced by double picosecond pulses with constant fluence and variable intervals. The crystallization degree is a function of the intervals of double pump laser pulses. The crystallization time decreased with the increasing of the intervals of the pump pulses. We believe that acoustic phonons play a key role in the crystallization process. - Highlights: • The double pulse crystallization is easier than the single pulse crystallization. • The crystallization is a function of the intervals of double pump laser pulses. • The crystallization time decreases with the increase of the pump pulse intervals. • Acoustic phonons play a key role in the crystallization process.

  8. Fast reconstruction of a bounded ultrasonic beam using acoustically induced piezo-luminescence

    Energy Technology Data Exchange (ETDEWEB)

    Kersemans, Mathias, E-mail: Mathias.Kersemans@UGent.be; Lammens, Nicolas; Degrieck, Joris; Van Paepegem, Wim [Mechanics of Materials and Structures MMS, Department of Materials Science and Engineering, Ghent University, Technologiepark 903, 9052 Zwijnaarde (Belgium); Smet, Philippe F. [LumiLab, Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, 9000 Gent (Belgium)

    2015-12-07

    We report on the conversion of ultrasound into light by the process of piezo-luminescence in epoxy with embedded BaSi{sub 2}O{sub 2}N{sub 2}:Eu as active component. We exploit this acoustically induced piezo-luminescence to visualize several cross-sectional slices of the radiation field of an ultrasonic piston transducer (f = 3.3 MHz) in both the near-field and the far-field. Simply combining multiple slices then leads to a fast representation of the 3D spatial radiation field. We have confronted the luminescent results with both scanning hydrophone experiments and digital acoustic holography results, and obtained a good correlation between the different approaches.

  9. Temperature and Pressure Dependence of Signal Amplitudes for Electrostriction Laser-Induced Thermal Acoustics

    Science.gov (United States)

    Herring, Gregory C.

    2015-01-01

    The relative signal strength of electrostriction-only (no thermal grating) laser-induced thermal acoustics (LITA) in gas-phase air is reported as a function of temperature T and pressure P. Measurements were made in the free stream of a variable Mach number supersonic wind tunnel, where T and P are varied simultaneously as Mach number is varied. Using optical heterodyning, the measured signal amplitude (related to the optical reflectivity of the acoustic grating) was averaged for each of 11 flow conditions and compared to the expected theoretical dependence of a pure-electrostriction LITA process, where the signal is proportional to the square root of [P*P /( T*T*T)].

  10. Application of Piezoelectric Materials in a Novel Linear Ultrasonic Motor based on Shear-induced Vibration Mode

    Institute of Scientific and Technical Information of China (English)

    CHEN Chao; SHI Yunlai; CHEN Haipeng; ZHAO Chunsheng

    2014-01-01

    A novel linear ultrasonic motor based on d15 effect of piezoelectric materials was presented. The design idea aimed at the direct utilization of the shear-induced vibration modes of piezoelectric material. Firstly, the inherent electromechanical coupling mechanism of piezoelectric material was investigated, and shear vibration modes of a piezoelectric shear block was specially designed. A driving point’s elliptical trajectory induced by shear vibration modes was discussed. Then a dynamic model for the piezoelectric shear stator was established with finite element (FE) method to conduct the parametric optimal design. Finally, a prototype based on d15 converse piezoelectric effect is manufactured, and the modal experiment of piezoelectric stator was conducted with laser doppler vibrometer. The experimental results show that the calculated shear-induced vibration modes can be excited completely, and the new linear ultrasonic motor reaches a speed 118 mm/s at no-load, and maximal thrust 12.8 N.

  11. Experiments on Interaction Between Current-Induced Vibration and Scour of Submarine Pipelines on Sandy Bottom

    Institute of Scientific and Technical Information of China (English)

    SHEN Zhonghan; LIU Yubiao; LI Qingping; HUANG Qinghua; ZHU Farong

    2000-01-01

    In order to understand the dynamic behavior of submarine pipelines exposed to current and the mechanism of the interaction between current-induced vibration and scour of pipelines on a sandy bottom, an experimental investigation is conducted with a small scale model. A test model which can be testedin the flume is set up by taking into account the typical working conditions of the pipelines and by applying the similarity theory. The interactions between the shape of the scour hole and the behavior of the pipeline as well as the flow patterns of the current are detailed, and the interaction mechanism outlined.The effect of vibration of the pipeline on the development of dynamic scour at different stages is found out. The proposed experimental method and test results provide an effective means for design of marine pipelines against scouring.

  12. Self-similar vortex-induced vibrations of a hanging string

    CERN Document Server

    Grouthier, Clement; Modarres-Sadeghi, Yahya; de Langre, Emmanuel

    2013-01-01

    An experimental analysis of the vortex-induced vibrations of a hanging string with variable tension along its length is presented in this paper. It is shown that standing waves develop along the hanging string. The evolution of the Strouhal number St with the Reynolds number Re first follows a trend similar to what is observed for a circular cylinder in a flow for relatively low Reynolds numbers (32vibrations along the hanging string is then explained theoretically by performing a linear stability analysis of an adapted wake-oscillator model. This linear stability analysis finally provides an accurate description of the mode shapes and of the evolution of the self-similarity coefficient with the flow speed.

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

    CERN Document Server

    Nemeth, Alexandra; 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 the two-dimensional electronic spectra we can attribute the observed modulations to periodic enhancement and decrement of the relative amplitudes of rephasing and non-rephasing contributions to the total response. Different metrics of the two-dimensional signals are shown to relate to the frequency-frequency correlation function which provides the connection between experimentally accessible observations and the underlying microscopic molecular dynamics. A detailed theory of the time-dependent two-dimensional spectral li...

  14. Modeling and control of flow-induced vibrations of a flexible hydrofoil in viscous flow

    Science.gov (United States)

    Caverly, Ryan James; Li, Chenyang; Chae, Eun Jung; Forbes, James Richard; Young, Yin Lu

    2016-06-01

    In this paper, a reduced-order model (ROM) of the flow-induced vibrations of a flexible cantilevered hydrofoil is developed and used to design an active feedback controller. The ROM is developed using data from high-fidelity viscous fluid-structure interaction (FSI) simulations and includes nonlinear terms to accurately capture the effect of lock-in. An active linear quadratic Gaussian (LQG) controller is designed based on a linearization of the ROM and is implemented in simulation with the ROM and the high-fidelity viscous FSI model. A controller saturation method is also presented that ensures that the control force applied to the system remains within a prescribed range. Simulation results demonstrate that the LQG controller successfully suppresses vibrations in both the ROM and viscous FSI simulations using a reasonable amount of control force.

  15. Numerical and experimental investigation of natural flow-induced vibrations of flexible hydrofoils

    Science.gov (United States)

    Chae, Eun Jung; Akcabay, Deniz Tolga; Lelong, Alexandra; Astolfi, Jacques Andre; Young, Yin Lu

    2016-07-01

    The objective of this work is to present combined numerical and experimental studies of natural flow-induced vibrations of flexible hydrofoils. The focus is on identifying the dependence of the foil's vibration frequencies and damping characteristics on the inflow velocity, angle of attack, and solid-to-fluid added mass ratio. Experimental results are shown for a cantilevered polyacetate (POM) hydrofoil tested in the cavitation tunnel at the French Naval Academy Research Institute (IRENav). The foil is observed to primarily behave as a chordwise rigid body and undergoes spanwise bending and twisting deformations, and the flow is observed to be effectively two-dimensional (2D) because of the strong lift retention at the free tip caused by a small gap with a thickness less than the wall boundary layer. Hence, the viscous fluid-structure interaction (FSI) model is formulated by coupling a 2D unsteady Reynolds-averaged Navier-Stokes (URANS) model with a two degree-of-freedom (2-DOF) model representing the spanwise tip bending and twisting deformations. Good agreements were observed between viscous FSI predictions and experimental measurements of natural flow-induced vibrations in fully turbulent and attached flow conditions. The foil vibrations were found to be dominated by the natural frequencies in absence of large scale vortex shedding due to flow separation. The natural frequencies and fluid damping coefficients were found to vary with velocity, angle of attack, and solid-to-fluid added mass ratio. In addition, the numerical results showed that the in-water to in-air natural frequency ratios decreased rapidly, and the fluid damping coefficients increased rapidly, as the solid-to-fluid added mass ratio decreases. Uncoupled mode (UM) linear potential theory was found to significantly over-predict the fluid damping for cases of lightweight flexible hydrofoils, and this over-prediction increased with higher velocity and lower solid-to-fluid added mass ratio.

  16. Raynaud's phenomenon among men and women with noise-induced hearing loss in relation to vibration exposure.

    Science.gov (United States)

    Pettersson, Hans; Burström, Lage; Nilsson, Tohr

    2014-01-01

    Raynaud's phenomenon is characterized by constriction in blood supply to the fingers causing finger blanching, of white fingers (WF) and is triggered by cold. Earlier studies found that workers using vibrating hand-held tools and who had vibration-induced white fingers (VWF) had an increased risk for hearing loss compared with workers without VWF. This study examined the occurrence of Raynaud's phenomenon among men and women with noise-induced hearing loss in relation to vibration exposure. All 342 participants had a confirmed noise-induced hearing loss medico legally accepted as work-related by AFA Insurance. Each subject answered a questionnaire concerning their health status and the kinds of exposures they had at the time when their hearing loss was first discovered. The questionnaire covered types of exposures, discomforts in the hands or fingers, diseases and medications affecting the blood circulation, the use of alcohol and tobacco and for women, the use of hormones and whether they had been pregnant. The participation rate was 41% (n = 133) with 38% (n = 94) for men and 50% (n = 39) for women. 84 men and 36 women specified if they had Raynaud's phenomenon and also if they had used hand-held vibrating machines. Nearly 41% of them had used hand-held vibrating machines and 18% had used vibrating machines at least 2 h each workday. There were 23 men/6 women with Raynaud's phenomenon. 37% reported WF among those participants who were exposed to hand-arm vibration (HAV) and 15% among those not exposed to HAV. Among the participants with hearing loss with daily use of vibrating hand-held tools more than twice as many reports WF compared with participants that did not use vibrating hand-held tools. This could be interpreted as Raynaud's phenomenon could be associated with an increased risk for noise-induced hearing loss. However, the low participation rate limits the generalization of the results from this study.

  17. Wind-induced vibration control of long-span power transmission towers

    Institute of Scientific and Technical Information of China (English)

    YIN Peng; LI Li; HU Liang-xia

    2009-01-01

    We investigated wind-induced vibration control of long-span power transmission towers based on a case study of the Jingdongnan-Nanyang-Jingmen 1000 kV transmission line project in P. R. China. The height of the cup tower is 181 m with a ground elevation of 47 m, which makes it a super flexible and wind-sensitive structure. Therefore, we should analyze the wind-resistant capacity of the system. We simulated applicable transverse fluctuating wind velocity field, developed a lead-rubber damper (LRD) for controlling wind-induced vibration of long-span transmission towers, deduced LRD calculation model parameter, and researched the best layout scheme and installation method of LRD. To calculate the wind-induced response of tower-line coupling system in seven layout schemes, we used the time history analysis method, and obtained the efficiencies of wind-induced vibration control. LRD deformation research proved that the damp of all LRDs was efficient under the designed wind velocity when they were laid along the edge of tower heads. We studied the controlling efficiency resulting from only applying stiffness to the tower poles where the dampers used to be laid under the designed wind velocity. The results show that the controlling efficiency was not ideal when the stiffness is increased on the poles only. Therefore, LRD should contribute to both the stiffness and damp of a structure to effectively reduce the dynamic response of a tower-line coupling system under strong winds. We also discussed the controlling efficiency of LRD under static winds. The results show that there was little difference between displacements derived by the finite element time history method and those obtained by static wind method conducted by a design institute. This means the simulation on space relevant wind velocity field was accurate and reasonable.

  18. Acoustic radiation- and streaming-induced microparticle velocities determined by microparticle image velocimetry in an ultrasound symmetry plane

    DEFF Research Database (Denmark)

    Barnkob, Rune; Augustsson, Per; Laurell, Thomas;

    2012-01-01

    We present microparticle image velocimetry measurements of suspended microparticles of diameters from 0.6 to 10μm undergoing acoustophoresis in an ultrasound symmetry plane in a microchannel. The motion of the smallest particles is dominated by the Stokes drag from the induced acoustic streaming...... flow, while the motion of the largest particles is dominated by the acoustic radiation force. For all particle sizes we predict theoretically how much of the particle velocity is due to radiation and streaming, respectively. These predictions include corrections for particle-wall interactions...... and ultrasonic thermoviscous effects and match our measurements within the experimental uncertainty. Finally, we predict theoretically and confirm experimentally that the ratio between the acoustic radiation- and streaming-induced particle velocities is proportional to the actuation frequency, the acoustic...

  19. Acoustic radiation- and streaming-induced microparticle velocities determined by micro-PIV in an ultrasound symmetry plane

    CERN Document Server

    Barnkob, Rune; Laurell, Thomas; Bruus, Henrik

    2012-01-01

    We present micro-PIV measurements of suspended microparticles of diameters from 0.6 um to 10 um undergoing acoustophoresis in an ultrasound symmetry plane in a microchannel. The motion of the smallest particles are dominated by the Stokes drag from the induced acoustic streaming flow, while the motion of the largest particles are dominated by the acoustic radiation force. For all particle sizes we predict theoretically how much of the particle velocity is due to radiation and streaming, respectively. These predictions include corrections for particle-wall interactions and ultrasonic thermoviscous effects, and they match our measurements within the experimental uncertainty. Finally, we predict theoretically and confirm experimentally that the ratio between the acoustic radiation- and streaming-induced particle velocities is proportional to the square of the particle size, the actuation frequency and the acoustic contrast factor, while it is inversely proportional to the kinematic viscosity.

  20. A Study on the Uncertainty of Flow-Induced Vibration in a Cross Flow over Staggered Tubes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ji-Su; Park, Jong-Woon [Dongguk univ, Gyeong Ju (Korea, Republic of); Choi, Hyeon-Kyeong [HanNam University, Daejeon (Korea, Republic of)

    2015-05-15

    Cross-flow in many support columns of very high temperature reactor (VHTR) lower plenum would have FIV issues under high speed flow jetting from the core. For a group of multiple circular cylinders subjected to a cross-flow, three types of potential vibration mechanisms may exist: (1) Vortex-induced vibration (VIV), (2) Fluid-elastic vibration (FEV) and (3) Turbulence-induced vibration (TIV). Kevalahan studied the free vibration of circular cylinders in a tightly packed periodic square inline array of cylinders. Pandey et al. studied the flue gas flow distribution in the Low Temperature Super Heater (LTSH) tube bundles situated in second pass of a utility boiler and the phenomenon of flow induced vibration. Nakamura et al. studied flow instability of cylinder arrays resembling U-bend tubes in steam generators. The FIV evaluation is usually performed with computational fluid dynamic (CFD) analysis to obtain unknown frequency of oscillation of the multiple objects under turbulent flow and thus the uncertainty residing in the turbulence model used should be quantified. In this paper, potential FIV uncertainty arising from the turbulence phenomena are evaluated for a typical cross flow through staggered tube bundles resembling the VHTR lower plenum support columns. Flow induced vibration (FIV) is one of the important mechanical and fatigue issues in nuclear systems. Especially, cross-flow in many support structures of VHTR lower plenum would have FIV issues under highly turbulent jet flows from the core. The results show that the effect of turbulence parameters on FIV is not negligible and the uncertainty is 5 to 10%. Present method can be applied to future FIV evaluations of nuclear systems. More extensive studies on flow induced vibration in a plant scale by using more rigorous computational methods are under way.

  1. Acoustics of friction.

    Science.gov (United States)

    Akay, Adnan

    2002-04-01

    This article presents an overview of the acoustics of friction by covering friction sounds, friction-induced vibrations and waves in solids, and descriptions of other frictional phenomena related to acoustics. Friction, resulting from the sliding contact of solids, often gives rise to diverse forms of waves and oscillations within solids which frequently lead to radiation of sound to the surrounding media. Among the many everyday examples of friction sounds, violin music and brake noise in automobiles represent the two extremes in terms of the sounds they produce and the mechanisms by which they are generated. Of the multiple examples of friction sounds in nature, insect sounds are prominent. Friction also provides a means by which energy dissipation takes place at the interface of solids. Friction damping that develops between surfaces, such as joints and connections, in some cases requires only microscopic motion to dissipate energy. Modeling of friction-induced vibrations and friction damping in mechanical systems requires an accurate description of friction for which only approximations exist. While many of the components that contribute to friction can be modeled, computational requirements become prohibitive for their contemporaneous calculation. Furthermore, quantification of friction at the atomic scale still remains elusive. At the atomic scale, friction becomes a mechanism that converts the kinetic energy associated with the relative motion of surfaces to thermal energy. However, the description of the conversion to thermal energy represented by a disordered state of oscillations of atoms in a solid is still not well understood. At the macroscopic level, friction interacts with the vibrations and waves that it causes. Such interaction sets up a feedback between the friction force and waves at the surfaces, thereby making friction and surface motion interdependent. Such interdependence forms the basis for friction-induced motion as in the case of

  2. Vibration-induced extra torque during electrically-evoked contractions of the human calf muscles

    Directory of Open Access Journals (Sweden)

    Kohn André F

    2010-06-01

    stimulation could be beneficial for many therapeutic interventions and vibration-based exercise programs. The command for the vibration-induced extra torques presumably activates spinal motoneurons following the size principle, which is a desirable feature for stimulation paradigms.

  3. Acoustics Noise Test Cell

    Data.gov (United States)

    Federal Laboratory Consortium — The Acoustic Noise Test Cell at the NASA/Caltech Jet Propulsion Laboratory (JPL) is located adjacent to the large vibration system; both are located in a class 10K...

  4. INVESTIGATION OF VORTEX SHEDDING INDUCED HYDRODYNAMIC VIBRATION IN VORTEX STREET FLOWMETER

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Vortex street flowmeter has been used in steady flo w measurement for about three decades. The benefits of this type of flowmeter i nclude high accuracy,good linearty,wide measuring range,and excellent reliabilit y. However,in unsteady flow measurement,the pressure disturbance as well as the noise from the system or surrounding can reduce the signal-to-noise ra tio of the flowmeter seriously. Aimed to use vortex street flowmeters in unstea dy flow measurement,the characteristics of the vortex shedding induced hydrodyna mic vibration around the prism bluff body in a vortex street flowmeter are inves tigated numerically and by expriments. The results show that the hydrodynamic vibrations with 180° phase shift occur at the axisymmetric points of the channe l around the bluff body. The most intense vibration occurs at the points on the lateral faces close to the base of the prism. The results provide therefore a useful reference for developing an anti-interference vortex flowmeter using the differential sensing technique.

  5. Railway vibrations induced into the soil: experiments, modelling and isolation. - Vibrations induites dans les sols par le trafic ferroviaire : exp\\'erimentations, mod\\'elisations et isolation

    CERN Document Server

    Semblat, Jean-François; Jacqueline, Delphine; Leblond, Jean-Jacques; Grasso, Eva

    2011-01-01

    Railway traffic induces cyclic and dynamic loadings in the track structure but also in the close environment (Degrande et al. 2006, Fran\\c{c}ois et al. 2007, Kausel 2008, Lefeuve-Mesgouez et al 2002, Paolucci et Spinelli 2006). The analysis of such excitations and their effects (e.g. vibrations, waves, etc) is fundamental to estimate their level and mitigate their potential consequences (settlements, nuisances, etc). After a brief summary of the current regulations, in situ experiments show the variability of the parameters characterizing the main phenomena (wave propagation into the soil, induced vibrations, etc). The main dynamic laboratory experiments are then discussed. They allow the estimation of the dynamic features of the materials (e.g. resonant column test), but also a simplified analysis of the main phenomena under controlled conditions (e.g. experiments in a geotechnical pit, centrifuge tests). The vibratory sources and the impedance ratios between the various soil layers (or some inclusions) bein...

  6. Comparative assessment of different treatment modalities in miners with vibration- and noise-induced disease

    Energy Technology Data Exchange (ETDEWEB)

    Velskaya, M.L.; Nekhorosheva, M.A.; Konovalova, S.I.; Kukhtina, G.V.; Gonchar, I.G.; Terentyeva, D.P.; Grishchenko, L.A.; Soboleva, N.P.; Kharitonov, S.A.; Priklonskiy, I.V.

    1985-02-01

    A group of 71 miners with vibration sickness and noise-induced pathology were managed either by standard methods, or in combination with acupuncture and/or hyperbaric oxygenation for a comparative assessment of the effectiveness of the different therapeutic approaches. Analysis of subjective factors as well as standard physiological parameters (EKG, rheoencephalography, peripheral rheography, EEG, neuropsychological tests) demonstrate that both acupuncture and hyperbaric oxygenation are effective modalities in the majority of the subjects. Nevertheless, the lack of improvement in certain criteria, or even what could be regarded as adverse sequelae, suggest that the use of hyperbaric oxygenation in the management of such disorders be approached with considerable care.

  7. Vibration-induced Kondo tunneling through metal-organic complexes with even electron occupation number.

    Science.gov (United States)

    Kikoin, K; Kiselev, M N; Wegewijs, M R

    2006-05-05

    We investigate transport through a mononuclear transition-metal complex with strong tunnel coupling to two electrodes. The ground state of this molecule is a singlet, while the first excited state is a triplet. We show that a modulation of the tunnel-barrier due to a molecular distortion which couples to the tunneling induces a Kondo-effect, provided the discrete vibrational energy compensates the singlet-triplet gap. We discuss the single-phonon and two-phonon-assisted cotunneling and possible experimental realization of the theory.

  8. Prediction of flow induced sound and vibration of periodically stiffened plates.

    Science.gov (United States)

    Maxit, Laurent; Denis, Vivien

    2013-01-01

    Stiffened structures excited by the turbulent boundary layer (TBL) occur very frequently in engineering applications; for instance, in the wings of airplanes or the pressure hulls of submarines. To improve knowledge of the interaction between stiffened structures and TBL, this paper deals with the modeling of infinite periodically stiffened plates excited by TBL. The mathematical formulation of the problem is well-established in the literature. The originality of the present work relies on the use of a wavenumber-point reciprocity technique for evaluating the response of the plate to convected harmonic pressure waves. It follows a methodology for estimating the vibro-acoustic response of the plate excited by the TBL from the wall pressure spectrum and its displacements in the wavenumber space due to point excitations located at the receiving positions. The computing process can be reduced to the numerical integration of an analytical expression in the case of a periodically stiffened plate. An application to a naval test case highlights the effect of Bloch-Floquet waves on the vibrations of the plate and its radiated pressure in the fluid.

  9. The liquid phase separation of Bi-Ga hypermonotectic alloy under acoustic levitation condition

    Institute of Scientific and Technical Information of China (English)

    HONG ZhenYu; L(U) YongJun; XIE WenJun; WEI BingBo

    2007-01-01

    Containerless treatment of Bi-58.5at%Ga hypermonotectic alloy is successfully performed with acoustic levitation technique. Under acoustic levitation condition, the second phase (Ga) distributes almost homogeneously in solidification sample, opposite to macrosegregation in solidification sample under conventional condition. Stokes motion of the second liquid droplet (Ga) is significantly restrained under acoustic levitation condition. The analyses indicate that the melt vibration in the gravity direction forced by acoustic field can induce steady flow around the second liquid droplet, which influences droplet shape during its moving upward and consequently restrains Stokes motion velocity of the second liquid droplet.

  10. Acoustically induced slip in sheared granular layers: Application to dynamic earthquake triggering

    Science.gov (United States)

    Ferdowsi, Behrooz; Griffa, Michele; Guyer, Robert A.; Johnson, Paul A.; Marone, Chris; Carmeliet, Jan

    2015-11-01

    A fundamental mystery in earthquake physics is "how can an earthquake be triggered by distant seismic sources?" Here we use discrete element method simulations of a granular layer, during stick slip, that is subject to transient vibrational excitation to gain further insight into the physics of dynamic earthquake triggering. Using Coulomb friction law for grains interaction, we observe delayed triggering of slip in the granular gouge. We find that at a critical vibrational amplitude (strain) there is an abrupt transition from negligible time-advanced slip (clock advance) to full clock advance; i.e., transient vibration and triggered slip are simultaneous. The critical strain is of order 10-6, similar to observations in the laboratory and in Earth. The transition is related to frictional weakening of the granular layer due to a dramatic decrease in coordination number and the weakening of the contact force network. Associated with this frictional weakening is a pronounced decrease in the elastic modulus of the layer. The study has important implications for mechanisms of triggered earthquakes and induced seismic events and points out the underlying processes in response of the fault gouge to dynamic transient stresses.

  11. Development of modified vibration test criteria for qualifying space vehicle components. [subjected to broadband random acoustic excitation

    Science.gov (United States)

    Chang, K. Y.; Kao, G. C.

    1974-01-01

    Simplified methods are described to estimate the test criteria of primary structures at component attachment points subjected to broadband random acoustic excitations. The current method utilizes a constant smeared component mass attenuation factor across the frequency range of interest. The developed method indicates that the attenuation factor is based on a frequency dependent ratio of the mechanical impedances of both the component and primary structures. The procedures used to predict the structural responses are considered as the present state-of-the-art and provide satisfactory prediction results. Example problems are used to illustrate the application procedures of the two methods and to compare the significant difference. It was found that the lower test criteria obtained by the impedance ratio method is due to the results of considering the effects of component/primary structure interaction.

  12. Simulation of Human-induced Vibrations Based on the Characterized In-field Pedestrian Behavior.

    Science.gov (United States)

    Van Nimmen, Katrien; Lombaert, Geert; De Roeck, Guido; Van den Broeck, Peter

    2016-04-13

    For slender and lightweight structures, vibration serviceability is a matter of growing concern, often constituting the critical design requirement. With designs governed by the dynamic performance under human-induced loads, a strong demand exists for the verification and refinement of currently available load models. The present contribution uses a 3D inertial motion tracking technique for the characterization of the in-field pedestrian behavior. The technique is first tested in laboratory experiments with simultaneous registration of the corresponding ground reaction forces. The experiments include walking persons as well as rhythmical human activities such as jumping and bobbing. It is shown that the registered motion allows for the identification of the time variant pacing rate of the activity. Together with the weight of the person and the application of generalized force models available in literature, the identified time-variant pacing rate allows to characterize the human-induced loads. In addition, time synchronization among the wireless motion trackers allows identifying the synchronization rate among the participants. Subsequently, the technique is used on a real footbridge where both the motion of the persons and the induced structural vibrations are registered. It is shown how the characterized in-field pedestrian behavior can be applied to simulate the induced structural response. It is demonstrated that the in situ identified pacing rate and synchronization rate constitute an essential input for the simulation and verification of the human-induced loads. The main potential applications of the proposed methodology are the estimation of human-structure interaction phenomena and the development of suitable models for the correlation among pedestrians in real traffic conditions.

  13. Vortex-induced vibration of a tube array with a large pitch-to-diameter ratio value

    Directory of Open Access Journals (Sweden)

    Bin Jiang

    2016-06-01

    Full Text Available To study the vortex-induced vibration behaviors of tube arrays with large pitch-to-diameter ratio values, an experiment has been conducted by testing the responses of an elastically mounted tube in a fixed normal triangular tube array with five rows and a pitch-to-diameter ratio value of 2.5 in a water tunnel subjected to cross-flow. The amplitude curves, power spectral density, and response frequencies were obtained in both in-line and transverse directions through the experiment. The results show that the responses obtained from the in-line direction are quite different from those obtained from the transverse direction. In the in-line vibration, there were two excitation regions, yet in the transverse vibration, there was only one excitation region. Moreover, in the in-line vibration, two obvious prominent peaks can be observed in the power spectral density of the vibration signal. The second prominent peak is a subharmonic peak. The frequency corresponding to the subharmonic peak was nearly twice as high as that corresponding to the first peak. However, in the transverse vibration, only a single broad peak existed in the power spectral density of the vibration signal. The hysteresis and the “lock-in” phenomena appeared in both the in-line and transverse vibrations. The results of study are beneficial for designing and operating devices mounted with large pitch-to-diameter ratio tube arrays, and for further research on the vortex-induced vibration of tube arrays.

  14. Three-dimensional vibration-induced vestibulo-ocular reflex identifies vertical semicircular canal dehiscence.

    Science.gov (United States)

    Aw, Swee Tin; Aw, Grace Elizabeth; Todd, Michael John; Bradshaw, Andrew Philip; Halmagyi, Gabor Michael

    2011-10-01

    Vertical semicircular canal dehiscence (VSCD) due to superior canal dehiscence (SCD) or posterior canal dehiscence (PCD) of the temporal bone causes vestibular and cochlear hypersensitivity to sound. This study aimed to characterize the vibration-induced vestibulo-ocular reflex (ViVOR) in VSCD. ViVORs in one PCD and 17 SCD patients, confirmed by CT imaging reformatted in semicircular canal planes, were measured with dual-search coils as binocular three-dimensional eye rotations induced by skull vibrations from a bone oscillator (B71-10 ohms) at 7 ms, 500 Hz, 135-dB peak-force level (re: 1 μN). The ViVOR eye rotation axes were computed by vector analysis and referenced to known semicircular canal planes. Onset latency of the ViVOR was 11 ms. ViVOR from VSCD was up to nine times greater than normal. The ViVOR's torsional rotation was always contraversive-torsional (the eye's upper pole rotated away from the stimulated ear), i.e. its direction was clockwise from a left and counterclockwise from a right VSCD, thereby lateralizing the side of the VSCD. The ViVORs vertical component distinguishes PCD from SCD, being downwards in PCD and upwards in SCD. In unilateral VSCD, the ViVOR eye rotation axis aligned closest to the dehiscent vertical semicircular canal axis from either ipsilateral or contralateral mastoid vibrations. However, in bilateral VSCDs, the ViVOR eye rotation axis lateralized to the ipsilateral dehiscent vertical semicircular canal axis. ViVOR was evoked in ossicular chain dysfunction, even when air-conducted click vestibulo-ocular reflex (VOR) was absent or markedly reduced. Hence, ViVOR could be a useful measurement to identify unilateral or bilateral VSCD even in the presence of ossicular chain dysfunction.

  15. The Skull Vibration-Induced Nystagmus Test of Vestibular Function—A Review

    Science.gov (United States)

    Dumas, Georges; Curthoys, Ian S.; Lion, Alexis; Perrin, Philippe; Schmerber, Sébastien

    2017-01-01

    A 100-Hz bone-conducted vibration applied to either mastoid induces instantaneously a predominantly horizontal nystagmus, with quick phases beating away from the affected side in patients with a unilateral vestibular loss (UVL). The same stimulus in healthy asymptomatic subjects has little or no effect. This is skull vibration-induced nystagmus (SVIN), and it is a useful, simple, non-invasive, robust indicator of asymmetry of vestibular function and the side of the vestibular loss. The nystagmus is precisely stimulus-locked: it starts with stimulation onset and stops at stimulation offset, with no post-stimulation reversal. It is sustained during long stimulus durations; it is reproducible; it beats in the same direction irrespective of which mastoid is stimulated; it shows little or no habituation; and it is permanent—even well-compensated UVL patients show SVIN. A SVIN is observed under Frenzel goggles or videonystagmoscopy and recorded under videonystagmography in absence of visual-fixation and strong sedative drugs. Stimulus frequency, location, and intensity modify the results, and a large variability in skull morphology between people can modify the stimulus. SVIN to 100 Hz mastoid stimulation is a robust response. We describe the optimum method of stimulation on the basis of the literature data and testing more than 18,500 patients. Recent neural evidence clarifies which vestibular receptors are stimulated, how they cause the nystagmus, and why the same vibration in patients with semicircular canal dehiscence (SCD) causes a nystagmus beating toward the affected ear. This review focuses not only on the optimal parameters of the stimulus and response of UVL and SCD patients but also shows how other vestibular dysfunctions affect SVIN. We conclude that the presence of SVIN is a useful indicator of the asymmetry of vestibular function between the two ears, but in order to identify which is the affected ear, other information and careful clinical judgment are

  16. Particle manipulation with acoustic vortex beam induced by a brass plate with spiral shape structure

    Science.gov (United States)

    Wang, Tian; Ke, Manzhu; Li, Weiping; Yang, Qian; Qiu, Chunyin; Liu, Zhengyou

    2016-09-01

    In this work, we give direct demonstration of acoustic radiation force and acoustic torque on particles exerted by an acoustic vortex beam, which is realized by an acoustic artificial structure plate instead of traditional transducer arrays. First, the first order acoustic vortex beam, which has the distinctive features of a linear and continuous phase variation from -π to π around its propagation axis and a magnitude null at its core, is obtained through one single acoustic source incident upon a structured brass plate with Archimedean spiral grating engraved on the back surface. Second, annular self-patterning of polystyrene particles with a radius of 90 μm is realized in the gradient field of this acoustic vortex beam. In addition, we further exhibit acoustic angular momentum transfer to an acoustic absorptive matter, which is verified by a millimeter-sized polylactic acid disk self-rotating in water in the acoustic field of the generated vortex beam.

  17. The vibrational signals that male fiddler crabs ( Uca lactea) use to attract females into their burrows

    Science.gov (United States)

    Takeshita, Fumio; Murai, Minoru

    2016-06-01

    In some fiddler crab species, males emit vibrations from their burrows to mate-searching females after they have attracted a female to the burrow entrance using a waving display. Although the vibrations are considered acoustic signals to induce mating, it has not been demonstrated whether the vibrations attract the females into the burrow and, consequently, influence females' mating decisions. We investigated the structures and patterns of the vibrations using a dummy female and demonstrated experimentally a female preference for male vibrations in Uca lactea in the field. The acoustic signals consisted of repetitions of pulses. The dominant frequency of the pulses decreased with male carapace width. The pulse length decreased slightly with an increasing number of vibrational repetitions, and the pulse interval increased with increasing repetitions. These factors imply that the vibrations convey information on male characteristics, such as body size and stamina. In the experiment on female mate choice, the females significantly preferred males with higher pulse repetition rates when they were positioned at the entrance of the burrow, indicating that the females use the male vibrational signals to decide whether to enter the burrow. However, females showed no preference for the vibrations once they were inside a burrow, i.e., whether they decided to copulate, suggesting that the vibrations do not independently affect a female's final decision of mate choice. The vibrations inside the burrow might influence a female's decision by interaction with other male traits such as the burrow structure.

  18. Hydrodynamic mechanism behind the suppression of vortex-induced vibration with permeable meshes

    Science.gov (United States)

    Assi, Gustavo R. S.; Cicolin, Murilo M.; Freire, Cesar M.

    2016-11-01

    Vortex-induced vibration (VIV) induces resonant vibrations on elastic bluff bodies when exposed to a flow. A VIV suppressor called "ventilated trousers" (VT) - consisting of a flexible net with tens of bobbins fitted every other node - has been developed as a commercial solution. Only a few experiments in the literature have evaluated the effectiveness of the VT, but very little is know about the underlying mechanism behind the suppression. Experiments have been carried out in a water channel with models of circular cylinders fitted with three different permeable meshes. VIV response and drag were obtained for models free to oscillate in the cross-flow direction with low mass and damping (Re = 5 , 000 to 25,000). All meshes achieved an average 50% reduction of the peak amplitude and reduced the mean drag when compared to that of a bare cylinder. PIV visualization of the wake revealed that the VT produced a much longer vortex-formation length, thus explaining its enhanced efficiency in suppressing VIV and reducing drag. The geometry and distribution of the bobbins proved to be important parameters. PIV also revealed the rich three-dimensional flow structures created by the bobbins that disrupt the formation of a coherent vortex wake. FAPESP 11/00205-6, 14/50279-4; CNPq 306917/2015-7.

  19. Effect of Internal Flow on Vortex-Induced Vibration of Submarine Free Spanning Pipelines

    Institute of Scientific and Technical Information of China (English)

    LOU Min; DING Jian; GUO Hai-yan; DONG Xiao-lin

    2005-01-01

    At present, most researches on the vortex-induced vibration of submarine free spanning pipelines ignore the effect of internal flowing fluid; furthermore, there are no research reports considering the coupling effect of internal and external fluid with the free span. In this paper, combining Iwan's wake oscillator model with the differential equation derived for the dynamic response of submarine free spanning pipelines with inclusion of internal flow, the pipe-fluid coupling equations are developed to investigate the effect of internal flow on the vortex-induced vibration of the free spans. The finite element approximation is implemented to derive the matrix equations of equilibrium. The Newmark method combined with simple iteration is used to solve the system of equations. The results indicate that the internal fluid flow may cause the shift of resonance band to the lower frequency and a slight decrease in the peak value; the effect will be more pronounced with the increase of the span length and can be weakened in the presence of the axial tension.

  20. 2-D Urans Simulations of Vortex Induced Vibrations of Circular Cylinder at Trsl3 Flow Regime

    Directory of Open Access Journals (Sweden)

    Omer Kemal Kinaci

    2016-01-01

    Full Text Available Research on vortex-induced vibrations (VIV mainly involves experimental science but building laboratory setups to investigate the flow are expensive and time consuming. Computational fluid dynamics (CFD methods may offer a faster and a cheaper way to understand this phenomenon depending on the solution approach to the problem. The context of this paper is to present the author’s computational approach to solve for vortex-induced vibrations which cover extensive explanations on the mathematical background, the grid structure and the turbulence models implemented. Current computational research on VIV for smooth cylinders is currently restricted to flows that have Reynolds numbers below 10,000. This paper describes the method to approach the problem with URANS and achieves to return satisfactory results for higher Reynolds numbers.The computational approach is first validated with a benchmark experimental study for rather low Reynolds number which falls into TrSL2 flow regime. Then, some numerical results up to Re=130,000, which falls into TrSL3 flow regime,are given at the end of the paper to reveal the validity of the approach for even higher Reynolds numbers.

  1. Vortex-Induced Vibration of a Circular Cylinder Fitted with a Single Spanwise Tripwire

    Science.gov (United States)

    Vaziri, Ehsan; Ekmekci, Alis

    2016-11-01

    A spanwise tripwire can be used to alter the coherence and strength of the vortex shedding from cylindrical structures. While this has been well-documented for cylinders in stationary state, there exists a lack of understanding regarding the control induced by spanwise tripwires for cylinders undergoing vortex-induced vibration (VIV). The current experimental research investigates the consequences of spanwise tripping on VIV of a cylinder. Experiments are conducted in a recirculating water tunnel at a Reynolds number of 10,000. The test setup allows the rigid test cylinder to have one-degree-of-freedom vibration in the cross-flow direction as a result of fluid forcing. To measure the cylinder motion, a high-resolution laser displacement sensor is used. The tripwire diameter to cylinder diameter ratio is fixed at 6.1%. Various angular positions of tripwire are studied ranging from 40 to 90 degrees. It is shown that the tripwire location controls the pattern, amplitude, frequency, and mid-position of oscillations significantly. Different oscillation modes are classified based on the observed oscillation pattern, amplitude and frequency. Oscillation amplitude can be reduced by 61% with respect to the amplitude of a clean cylinder undergoing VIV under the same flow condition.

  2. Experimental investigation of flow induced dust acoustic shock waves in a complex plasma

    CERN Document Server

    Jaiswal, S; Sen, A

    2016-01-01

    We report on experimental observations of flow induced large amplitude dust-acoustic shock waves (DASW) in a complex plasma. The experiments have been carried out in a $\\Pi$ shaped DC glow discharge experimental device using kaolin particles as the dust component in a background of Argon plasma. A strong supersonic 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 gas flow rate is used to trigger the onset of high velocity dust acoustic shocks whose dynamics are captured by fast video pictures of the evolving structures. The physical characteristics of these shocks are delineated through a parametric scan of their dynamical properties over a range of flow speeds and potential hill heights. The observed evolution of the shock waves and their propagation characteristics are found to compare well with model numerical results based on a m...

  3. Acoustic streaming with heat exchange

    Science.gov (United States)

    Gubaidullin, A. A.; Pyatkova, A. V.

    2016-10-01

    Acoustic streaming in a cylindrical cavity with heat exchange is numerically investigated. The cavity is filled with air. The boundaries of the cavity are maintained at constant temperature. The features of acoustic streaming manifesting with the decrease in the frequency of vibration in comparison with the resonant frequency are determined. The influence of the nonlinearity of process on acoustic streaming is shown. The nonlinearity is caused by the increase of the vibration amplitude.

  4. Application of time reversal mirror technique in microwave-induced thermo-acoustic tomography system

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Microwave-induced thermo-acoustic tomography (MITAT) is a promising technique with great potential in biomedical imaging. It has both the high contrast of the microwave imaging and the high resolution of the ultrasound imaging. In this paper, the proportional relationship between the absorbed microwave energy distribution and the induced ultrasound source distribution is derived. Further, the time reversal mirror (TRM) technique based on the pseudo-spectral time domain (PSTD) method is applied to MITAT system. The simulation results show that high contrast and resolution can be achieved by the TRM technique based on PSTD method even for the received signals with very low signal-to-noise ratio (SNR) and the model parameter with random fluctuation.

  5. The Impact of Traffic-Induced Bridge Vibration on Rapid Repairing High-Performance Concrete for Bridge Deck Pavement Repairs

    Directory of Open Access Journals (Sweden)

    Wei Wang

    2014-01-01

    Full Text Available Based on forced vibration tests for high-performance concrete (HPC, the influence of bridge vibration induced by traveling vehicle on compressive strength and durability of HPC has been studied. It is concluded that 1 d and 2 d compressive strength of HPC decreased significantly, and the maximum reduction rate is 9.1%, while 28 d compressive strength of HPC had a slight lower with a 3% maximal drop under the action of two simple harmonic vibrations with 2 Hz, 3 mm amplitude, and 4 Hz, 3 mm amplitude. Moreover, the vibration had a slight effect on the compressive strength of HPC when the simple harmonic vibration had 4 Hz and 1 mm amplitude; it is indicated that the amplitude exerts a more prominent influence on the earlier compressive strength with the comparison of the frequency. In addition, the impact of simple harmonic vibration on durability of HPC can be ignored; this shows the self-healing function of concrete resulting from later hydration reaction. Thus, the research achievements mentioned above can contribute to learning the laws by which bridge vibration affects the properties of concrete and provide technical support for the design and construction of the bridge deck pavement maintenance.

  6. Nearfield Acoustical Holography

    Science.gov (United States)

    Hayek, Sabih I.

    Nearfield acoustical holography (NAH) is a method by which a set of acoustic pressure measurements at points located on a specific surface (called a hologram) can be used to image sources on vibrating surfaces on the acoustic field in three-dimensional space. NAH data are processed to take advantage of the evanescent wavefield to image sources that are separated less that one-eighth of a wavelength.

  7. Study on Diesel Engine's Oil Pan's Modal of Acoustic-Liquid-Vibration Coupling System of Noise%柴油机油底壳声液振耦合系统噪声模态研究

    Institute of Scientific and Technical Information of China (English)

    胡启国; 李力克; 陈万德

    2013-01-01

    Noise analysis for the diesel engine oil pan casing vibration analysis only and ignore the lubricating fluid and cavity effects. The use of acoustic-liquid-vibration coupling finite element theory, coupling system element model is established of oil pan, oil and internal cavity of oil pan, and the modal of the finite element is analysised, then the vibration frequency of the oil pan is measured and analysised. Research oil pan system in the acoustic fluid coupled vibration mode was significantly lower vibration and noise enhancement, especially in the strong coupling 118.26 Hz modal frequencies. Lubricating fluid in the oil pan when the low-frequency sound vibration coupled system is less liquid, at high frequencies is more significant impact on the system.%针对柴油机油底壳噪声分析中只分析壳体振动而忽略了润滑液和空腔影响,利用声液振耦合有限元理论,建立油底壳结构有限元模型,润滑油、内部空腔声学有限元模型,油底壳声液振耦合系统有限元模型,并对各有限元模型进行模态研究,然后对实际油底壳振动频谱特性进行验证分析.通过研究得到油底壳在声液振耦合系统模态下振动和噪声值明显增强,特别是在118.26 Hz强耦合模态频率下.油底壳中润滑液在低频时对声液振耦合系统影响较小,在高频时对系统影响较为明显.

  8. The ecological and evolutionary consequences of noise-induced acoustic habitat loss

    Science.gov (United States)

    Tennessen, Jennifer Beissinger

    negative physiological consequences, and that populations have adapted over short timescales to minimize the detrimental impacts of this novel pressure. Finally, I present results from a field acoustic playback experiment that show that noise from the invasive Cuban treefrog (Osteopilus septentrionalis ) differentially affects the vocal behavior of native anurans, with those with more similar calls being disproportionally more affected. Green treefrogs (Hyla cinerea) shortened their calls, called louder, and maintained call spacing (e.g. continued actively calling) during noise stimuli whereas pine woods treefrogs (H. femoralis) did not modify vocal behavior in response to any noise stimuli. Collectively, the results of these investigations (1) provide insight into the extent of noise-induced acoustic habitat loss in space and time, (2) reveal fitness-relevant individual- and population-level consequences of this form of habitat loss, and (3) show resiliency within ecological systems through the individual- and population-level responses to this novel pressure over short time-scales. These findings advance the field by illustrating how the spatiotemporal extent of anthropogenic noise impacts important ecological processes, and by demonstrating the resiliency of some species in responding rapidly to novel pressures.

  9. Friction-induced vibrations and self-organization mechanics and non-equilibrium thermodynamics of sliding contact

    CERN Document Server

    Nosonovsky, Michael

    2013-01-01

    Many scientists and engineers do not realize that, under certain conditions, friction can lead to the formation of new structures at the interface, including in situ tribofilms and various patterns. In turn, these structures-usually formed by destabilization of the stationary sliding regime-can lead to the reduction of friction and wear. Friction-Induced Vibrations and Self-Organization: Mechanics and Non-Equilibrium Thermodynamics of Sliding Contact combines the mechanical and thermodynamic methods in tribology, thus extending the field of mechanical friction-induced vibrations to non-mechani

  10. Development and modelisation of a hydro-power conversion system based on vortex induced vibration

    Science.gov (United States)

    Lefebure, David; Dellinger, Nicolas; François, Pierre; Mosé, Robert

    2016-11-01

    The Vortex Induced Vibration (VIV) phenomenon leads to mechanical issues concerning bluff bodies immerged in fluid flows and have therefore been studied by numerous authors. Moreover, an increasing demand for energy implies the development of alternative, complementary and renewable energy solutions. The main idea of EauVIV project consists in the use of VIV rather than its deletion. When rounded objects are immerged in a fluid flow, vortices are formed and shed on their downstream side, creating a pressure imbalance resulting in an oscillatory lift. A convertor modulus consists of an elastically mounted, rigid cylinder on end-springs, undergoing flow- induced motion when exposed to transverse fluid-flow. These vortices induce cyclic lift forces in opposite directions on the circular bar and cause the cylinder to vibrate up and down. An experimental prototype was developed and tested in a free-surface water channel and is already able to recover energy from free-stream velocity between 0.5 and 1 m.s -1. However, the large number of parameters (stiffness, damping coefficient, velocity of fluid flow, etc.) associated with its performances requires optimization and we choose to develop a complete tridimensionnal numerical model solution. A 3D numerical model has been developed in order to represent the real system behavior and improve it through, for example, the addition of parallel cylinders. The numerical model build up was carried out in three phases. The first phase consists in establishing a 2D model to choose the turbulence model and quantify the dependence of the oscillations amplitudes on the mesh size. The second corresponds to a 3D simulation with cylinder at rest in first time and with vertical oscillation in a second time. The third and final phase consists in a comparison between the experimental system dynamic behavior and its numerical model.

  11. Flow induced vibration and stability analysis of multi wall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Yun, Kyung Jae [Agency for Defense Development, Daejeon (Korea, Republic of); Choi, Jong Woon [Korean Intellectual Property Office, Daejeon (Korea, Republic of); Kim, Sung Kyun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Song, Oh Seop [Chungnam National Univ., Daejeon (Korea, Republic of)

    2012-12-15

    The free vibration and flow induced flutter instability of cantilever multi wall carbon nanotubes conveying fluid are investigated and the nanotubes are modeled as thin-walled beams. The non-classical effects of the transverse shear, rotary inertia, warping inhibition, and van der Waals forces between two walls are incorporated into the structural model. The governing equations and associated boundary conditions are derived using Hamilton's principle. A numerical analysis is carried out by using the extended Galerkin method, which enables us to obtain more accurate solutions compared to the conventional Galerkin method. Cantilevered carbon nanotubes are damped with decaying amplitude for a flow velocity below a certain critical value. However, beyond this critical flow velocity, flutter instability may occur. The variations in the critical flow velocity with respect to both the radius ratio and length of the carbon nanotubes are investigated and pertinent conclusions are outlined. The differences in the vibration and instability characteristics between the Timoshenko beam theory and Euler beam theory are revealed. A comparative analysis of the natural frequencies and flutter characteristics of MWCNTs and SWCNTs is also performed.

  12. Exact analytical solution of shear-induced flexural vibration of functionally graded piezoelectric beam

    Science.gov (United States)

    Sharma, Pankaj; Parashar, Sandeep Kumar

    2016-05-01

    The priority of this paper is to obtain the exact analytical solution for free flexural vibration of FGPM beam actuated using the d15 effect. In piezoelectric actuators, the potential use of d15 effect has been of particular interest for engineering applications since shear piezoelectric coefficient d15 is much higher than the other piezoelectric coupling constants d31 and d33. The applications of shear actuators are to induce and control the flexural vibrations of beams and plates. In this study, a modified Timoshenko beam theory is used where electric potential is assumed to vary sinusoidaly along the thickness direction. The material properties are assumed to be graded across the thickness in accordance with power law distribution. Hamilton`s principle is employed to obtain the equations of motion along with the associated boundary conditions for FGPM beams. Exact analytical solution is derived thus obtained equations of motion. Results for clamped-clamped and clamped-free boundary conditions are presented. The presented result and method shell serve as benchmark for comparing the results obtained from the other approximate methods.

  13. Lift Enhancement and Oscillatory Suppression of Vortex-induced Vibration in Shear Flow by Loentz Force

    Institute of Scientific and Technical Information of China (English)

    张辉; 范宝春; 李鸿志

    2012-01-01

    The flow of the weak electrolyte solution can be controlled by Lorentz force achieved with the suitable magnetic and electric fields, and it has the advantages of vortex street suppression, drag reduction, lift enhancement and oscillatory suppression for the flow over a bluff body. The electro-magnetic control of vortex-induced vibration (VIV) of a circular cyl- inder in the shear flow was investigated numerically in the exponential-polar coordinates attached on the moving cylinder for Re = 150. With the effect of background vorticity, the vortex street of VIV cylinder was composed of two parallel rows with an opposite sign of the vortices which inclines toward the lower side and the strength of upper vortex is larger than that of lower vortex. The lift force vibrated periodically with the effect of vortex shedding and the mean value was negative due to the background vorticity. The Lorentz force for controlling the VIV cylinder was classified into the field Lorentz force and the wall Lorentz force. The field Lorentz force suppresses the lift oscillation, and in turn, suppresses the VIV, whereas the wall Loreutz force increases the lift.

  14. On the Shaker Simulation of Wind-Induced Non-Gaussian Random Vibration

    Directory of Open Access Journals (Sweden)

    Fei Xu

    2016-01-01

    Full Text Available Gaussian signal is produced by ordinary random vibration controllers to test the products in the laboratory, while the field data is usually non-Gaussian. Two methodologies are presented in this paper for shaker simulation of wind-induced non-Gaussian vibration. The first methodology synthesizes the non-Gaussian signal offline and replicates it on the shaker in the Time Waveform Replication (TWR mode. A new synthesis method is used to model the non-Gaussian signal as a Gaussian signal multiplied by an amplitude modulation function (AMF. A case study is presented to show that the synthesized non-Gaussian signal has the same power spectral density (PSD, probability density function (PDF, and loading cycle distribution (LCD as the field data. The second methodology derives a damage equivalent Gaussian signal from the non-Gaussian signal based on the fatigue damage spectrum (FDS and the extreme response spectrum (ERS and reproduces it on the shaker in the closed-loop frequency domain control mode. The PSD level and the duration time of the derived Gaussian signal can be manipulated for accelerated testing purpose. A case study is presented to show that the derived PSD matches the damage potential of the non-Gaussian environment for both fatigue and peak response.

  15. Wake reconfiguration downstream of an inclined flexible cylinder at the onset of vortex-induced vibrations

    Science.gov (United States)

    Bourguet, Remi; Triantafyllou, Michael

    2016-11-01

    Slender flexible cylinders immersed in flow are common in nature (e.g. plants and trees in wind) and in engineering applications, for example in the domain of offshore engineering, where risers and mooring lines are exposed to ocean currents. Vortex-induced vibrations (VIV) naturally develop when the cylinder is placed at normal incidence but they also appear when the body is inclined in the current, including at large angles. In a previous work concerning a flexible cylinder inclined at 80 degrees, we found that the occurrence of VIV is associated with a profound alteration of the flow dynamics: the wake exhibits a slanted vortex shedding pattern in the absence of vibration, while the vortices are shed parallel to the body once the large-amplitude VIV regime is reached. The present study aims at bridging the gap between these two extreme configurations. On the basis of direct numerical simulations, we explore the intermediate states of the flow-structure system. We identify two dominant components of the flow: a high-frequency component that relates to the stationary body wake and a low-frequency component synchronized with body motion. We show that the scenario of flow reconfiguration is driven by the opposite trends of these two component contributions.

  16. Electronic, structural and vibrational induced effects upon ionization of 2-quinolinone

    Science.gov (United States)

    Bellili, A.; Pan, Y.; Al Mogren, M. M.; Lau, K. C.; Hochlaf, M.

    2016-07-01

    Using first principle methodologies, we characterize the lowest electronic states of 2-quinolinone+ cation. The ground state of this ion is of X˜2A″ nature. We deduce the adiabatic ionization energy of 2-quinolinone to be equal 8.249 eV using the explicitly correlated coupled cluster level and where zero point vibrational energy, core-valence and scalar relativistic effects are taken into account. We examine also the ionization induced structural changes and vibrational shifts and analyze the electron density differences between the neutral and ionic species. These data show that the formation of 2-quinolinone+X˜2A″ from 2-quinolinone affects strongly the HNCO group, whereas the carbon skeletal is perturbed when the upper electronic cationic states are populated. The comparison to 2-pyridone allows the elucidation of the effect of benzene ring fused with this heterocyclic ring. Since quinolones and pyridones are both model systems of DNA bases, these findings might help in understanding the charge redistribution in these biological entities upon ionization.

  17. Illusory movements induced by tendon vibration in right- and left-handed people.

    Science.gov (United States)

    Tidoni, Emmanuele; Fusco, Gabriele; Leonardis, Daniele; Frisoli, Antonio; Bergamasco, Massimo; Aglioti, Salvatore Maria

    2015-02-01

    Frequency-specific vibratory stimulation of peripheral tendons induces an illusion of limb movement that may be useful for restoring proprioceptive information in people with sensorimotor disability. This potential application may be limited by inter- and intra-subject variability in the susceptibility to such an illusion, which may depend on a variety of factors. To explore the influence of stimulation parameters and participants' handedness on the movement illusion, we vibrated the right and left tendon of the biceps brachii in a group of right- and left-handed people with five stimulation frequencies (from 40 to 120 Hz in step of 20 Hz). We found that all participants reported the expected illusion of elbow extension, especially after 40 and 60 Hz. Left-handers exhibited less variability in reporting the illusion compared to right-handers across the different stimulation frequencies. Moreover, the stimulation of the non-dominant arm elicited a more vivid illusion with faster onset relative to the stimulation of the dominant arm, an effect that was independent from participants' handedness. Overall, our data show that stimulation frequency, handedness and arm dominance influence the tendon vibration movement illusion. The results are discussed in reference to their relevance in linking motor awareness, improving current devices for motor ability recovery after brain or spinal damage and developing prosthetics and virtual embodiment systems.

  18. Artificial piezoelectric grass for energy harvesting from turbulence-induced vibration

    Science.gov (United States)

    Hobeck, J. D.; Inman, D. J.

    2012-10-01

    The primary objective of this research is to develop a deploy-and-forget energy harvesting device for use in low-velocity, highly turbulent fluid flow environments i.e. streams or ventilation systems. The work presented here focuses on a novel, lightweight, highly robust, energy harvester design referred to as piezoelectric grass. This biologically inspired design consists of an array of cantilevers, each constructed with piezoelectric material. When exposed to proper turbulent flow conditions, these cantilevers experience vigorous vibrations. Preliminary results have shown that a small array of piezoelectric grass was able to produce up to 1.0 mW per cantilever in high-intensity turbulent flow having a mean velocity of 11.5 m s-1. According to the literature, this is among the highest output achieved using similar harvesting methods. A distributed parameter model for energy harvesting from turbulence-induced vibration will be introduced and experimentally validated. This model is generalized for the case of a single cantilever in turbulent cross-flow. Two high-sensitivity pressure probes were needed to perform spectral measurements within various turbulent flows. The design and performance of these probes along with calibration and measurement techniques will be discussed.

  19. Microwave-induced thermal acoustic tomography for breast tumor based on compressive sensing.

    Science.gov (United States)

    Zhu, Xiaozhang; Zhao, Zhiqin; Wang, Jinguo; Song, Jian; Liu, Qing Huo

    2013-05-01

    Microwave-induced thermal acoustic tomography (MITAT) is an innovative technique to image biomedical tissues based on their electric properties. It has the advantages of both high contrast and high spatial resolution. Image reconstruction method in MITAT is always a critical issue. In this paper, a CS-MITAT (CS: compressive sensing) imaging method is proposed. Compressive sensing (CS) is a recently developed sparse signal representation and analysis framework which handles medical imaging measurements using low sampling rate or increasing imaging quality. The CS-MITAT imaging method applies CS theory to the MITAT for breast tumor imaging. In this method, an over-complete dictionary is established to make sparse measurements in the spatial domain. This treatment greatly saves measurement time. Simulations and experiments with real breast tumor tissues demonstrate the feasibility and effectiveness of the method. Compared with conventional time reversal mirror method which has been used in MITAT research, CS-MITAT provides the same peak signal-to-noise ratio imaging quality by using significantly fewer acoustic sensor positions or scanning times.

  20. The influence of friction at the ice-structure interface on the induced vibrations

    NARCIS (Netherlands)

    Hendrikse, H.; Metrikine, A.V.

    2013-01-01

    Vertically-sided offshore structures occasionally experience sustained vibration due to drifting ice sheets crushing against them. These vibrations may lead to problems associated with structural integrity and safety. Traditionally, three regimes of interaction are distinguished: intermittent crushi

  1. Raynaud′s phenomenon among men and women with noise-induced hearing loss in relation to vibration exposure

    Directory of Open Access Journals (Sweden)

    Hans Pettersson

    2014-01-01

    Full Text Available Raynaud′s phenomenon is characterized by constriction in blood supply to the fingers causing finger blanching, of white fingers (WF and is triggered by cold. Earlier studies found that workers using vibrating hand-held tools and who had vibration-induced white fingers (VWF had an increased risk for hearing loss compared with workers without VWF. This study examined the occurrence of Raynaud′s phenomenon among men and women with noise-induced hearing loss in relation to vibration exposure. All 342 participants had a confirmed noise-induced hearing loss medico legally accepted as work-related by AFA Insurance. Each subject answered a questionnaire concerning their health status and the kinds of exposures they had at the time when their hearing loss was first discovered. The questionnaire covered types of exposures, discomforts in the hands or fingers, diseases and medications affecting the blood circulation, the use of alcohol and tobacco and for women, the use of hormones and whether they had been pregnant. The participation rate was 41% (n = 133 with 38% (n = 94 for men and 50% (n = 39 for women. 84 men and 36 women specified if they had Raynaud′s phenomenon and also if they had used hand-held vibrating machines. Nearly 41% of them had used hand-held vibrating machines and 18% had used vibrating machines at least 2 h each workday. There were 23 men/6 women with Raynaud′s phenomenon. 37% reported WF among those participants who were exposed to hand-arm vibration (HAV and 15% among those not exposed to HAV. Among the participants with hearing loss with daily use of vibrating hand-held tools more than twice as many reports WF compared with participants that did not use vibrating hand-held tools. This could be interpreted as Raynaud′s phenomenon could be associated with an increased risk for noise-induced hearing loss. However, the low participation rate limits the generalization of the results from this study.

  2. Modelling the Source of Blasting for the Numerical Simulation of Blast-Induced Ground Vibrations: A Review

    Science.gov (United States)

    Ainalis, Daniel; Kaufmann, Olivier; Tshibangu, Jean-Pierre; Verlinden, Olivier; Kouroussis, Georges

    2017-01-01

    The mining and construction industries have long been faced with considerable attention and criticism in regard to the effects of blasting. The generation of ground vibrations is one of the most significant factors associated with blasting and is becoming increasingly important as mining sites are now regularly located near urban areas. This is of concern to not only the operators of the mine but also residents. Mining sites are subjected to an inevitable compromise: a production blast is designed to fragment the utmost amount of rock possible; however, any increase in the blast can generate ground vibrations which can propagate great distances and cause structural damage or discomfort to residents in surrounding urban areas. To accurately predict the propagation of ground vibrations near these sensitive areas, the blasting process and surrounding environment must be characterised and understood. As an initial step, an accurate model of the source of blast-induced vibrations is required. This paper presents a comprehensive review of the approaches to model the blasting source in order to critically evaluate developments in the field. An overview of the blasting process and description of the various factors which influence the blast performance and subsequent ground vibrations are also presented. Several approaches to analytically model explosives are discussed. Ground vibration prediction methods focused on seed waveform and charge weight scaling techniques are presented. Finally, numerical simulations of the blasting source are discussed, including methods to estimate blasthole wall pressure time-history, and hydrodynamic codes.

  3. The Effect of Internal Fluid on the Response of Vortex-Induced Vibration of Marine Risers

    Institute of Scientific and Technical Information of China (English)

    郭海燕; 王元斌; 傅强

    2004-01-01

    Based on Iwan′s wake oscillator model developed with the classical van der Pol equation, the differential equation for the response of the vortex-induced vibration (VIV) of the riser considering the effect of the internal flowing fluid and the external marine environmental condition is derived. The effect of the internal flowing fluid on the response of VIV of the riser is studied by means of the Finite Element Method. The results show that the effect of the internal fluid velocity on the VIV of the riser is strong when the natural frequency of the riser is close to the vortex shedding frequency. In addition, the increase of the top tension can decrease the sensitivity of the riser to the internal fluid velocity.

  4. Suppression of two-dimensional vortex-induced vibration with active velocity feedback controller

    Science.gov (United States)

    Ma, B.; Srinil, N.

    2016-09-01

    Vortex-induced vibrations (VIV) establish key design parameters for offshore and subsea structures subject to current flows. Understanding and predicting VIV phenomena have been improved in recent years. Further, there is a need to determine how to effectively and economically mitigate VIV effects. In this study, linear and nonlinear velocity feedback controllers are applied to actively suppress the combined cross-flow and in-line VIV of an elastically-mounted rigid circular cylinder. The strongly coupled fluid-structure interactions are numerically modelled and investigated using a calibrated reduced-order wake oscillator derived from the vortex strength concept. The importance of structural geometrical nonlinearities is studied which highlights the model ability in matching experimental results. The effectiveness of linear vs nonlinear controllers are analysed with regard to the control direction, gain and power. Parametric studies are carried out which allow us to choose the linear vs nonlinear control, depending on the target controlled amplitudes and associated power requirements.

  5. Numerical and Physical Investigation on Vortex-Induced Vibrations of Marine Risers

    Institute of Scientific and Technical Information of China (English)

    GUO Hai-yan; LOU Min; DONG Xiao-lin; QI Xiao-liang

    2006-01-01

    As a project supported by the National Natural Science Foundation of China, a model experiment on the vortex-induced vibration of practical risers transporting fluid in currents was conducted in the Physical Oceanography Laboratory of Ocean University of China in 2005. Because most of the offshore oil fields in China are in shallow water, the experiment was focused on the risers in shallow water. The similarity theory was used in the experiment to derive the experimental model from the practical model. Considering the internal flowing fluid and external marine environment, the dynamic response of the marine riser was measured. Corresponding numerical simulation was performed with the finite element method. Comparisons were made between the results from the experiment and numerical simulation.

  6. Harvesting microalgal biomass using a magnetically induced membrane vibration (MMV) system: filtration performance and energy consumption.

    Science.gov (United States)

    Bilad, M R; Discart, V; Vandamme, D; Foubert, I; Muylaert, K; Vankelecom, Ivo F J

    2013-06-01

    This study was performed to investigate the effectiveness of submerged microfiltration to harvest both a marine diatom Phaeodactylum tricornutum and a Chlorella vulgaris in a recently developed magnetically induced membrane vibrating (MMV) system. We assess the filtration performance by conducting the improved flux step method (IFM), fed-batch concentration filtrations and membrane fouling autopsy using two lab-made membranes with different porosity. The full-scale energy consumption was also estimated. Overall results suggest that the MMV offers a good fouling control and the process was proven to be economically attractive. By combining the membrane filtration (15× concentration) with centrifugation to reach a final concentration of 25% w/v, the energy consumption to harvest P. tricornutum and C. vulgaris was, respectively, as low as 0.84 and 0.77kWh/m(3), corresponding to 1.46 and 1.39 kWh/kg of the harvested biomass.

  7. NONLINEAR FLUID DAMPING IN STRUCTURE-WAKE OSCILLATORS IN MODELING VORTEX-INDUCED VIBRATIONS

    Institute of Scientific and Technical Information of China (English)

    LIN Li-ming; LING Guo-can; WU Ying-xiang; ZENG Xiao-hui

    2009-01-01

    A Nonlinear Fluid Damping(NFD)in the form of the square-velocity is applied in the response analysis of Vortex-Induced Vibrations(VIV).Its nonlinear hydrodynamic effects on the coupled wake and structure oscillators are investigated.A comparison between the coupled systems with the linear and nonlinear fluid dampings and experiments shows that the NFD model can well describe response characteristics,such as the amplification of body displacement at lock-in and frequency lock-in,both at high and low mass ratios.Particularly,the predicted peak amplitude of the body in the Griffin plot is in good agreement with experimental data and empirical equation,indicating the significant effect of the NFD on the structure motion.

  8. Flow-induced vibration for light water reactors. Final progress report, July 1981-September 1981

    Energy Technology Data Exchange (ETDEWEB)

    Torres, M.R.

    1981-11-01

    Flow-Induced Vibration for Light Water Reactors (FIV for LWRs) is a program designed to improve the FIV performance of light water reactors through the development of design criteria, analytical models for predicting behavior of components, and general scaling laws to improve the accuracy of reduced-scale tests, and through the identification of high FIV risk areas. The program is managed by the General Electric Nuclear Power Systems Engineering Department and has three major contributors: General Electric Nuclear Power Systems Engineering Department (NPSED), General Electric Corporate Research and Development (CR and D) and Argonne National Laboratory (ANL). The program commenced December 1, 1976. This progress report summarizes the accomplishments achieved during the final period from July 1981 to September 1981. This is the last quarterly progress report to be issued for this program.

  9. Optical Tracking Measurement on Vortex Induced Vibration of Flexible Riser with Short-Length Buoyance Module

    Science.gov (United States)

    Fan, Dixia; Du, Honglin; Triantafyllou, Michael

    2016-11-01

    We address experimentally the vortex induced vibrations (VIV) of long flexible cylinders. We employ optical tracking, using an array of high speed cameras. Compared to strain gauges and accelerometers, this non-intrusive approach, allows direct measurement of the flexible cylinder displacement with far denser spatial distribution. The measurements reveal essential features of flexible cylinder VIV, including complex geometries such as cylinders containing short-length buoyancy modules, with module to cylinder diameter ratio of 1:3.2 and module to bare cylinder length ratio of 1:1. The experiments are conducted with aspect ratio of 170 and 3 different coverage ratios, of 100%, 50% and 20%. The measurements demonstrate bi-frequency response due to excitation from both buoyancy module and bare cylinder, at low Strouhal number, down to values of 0.08, and the generation of traveling wave patterns.

  10. Orientation of bluff body for designing efficient energy harvesters from vortex-induced vibrations

    Energy Technology Data Exchange (ETDEWEB)

    Dai, H. L. [Department of Mechanics, Huazhong University of Science and Technology, Wuhan 430074 (China); School of Civil and Environmental Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Abdelkefi, A. [Department of Mechanical and Aerospace Engineering, New Mexico State University, Las Cruces, New Mexico 88003 (United States); Yang, Y., E-mail: cywyang@ntu.edu.sg [School of Civil and Environmental Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Wang, L. [Department of Mechanics, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2016-02-01

    The characteristics and performances of four distinct vortex-induced vibrations (VIVs) piezoelectric energy harvesters are experimentally investigated and compared. The difference between these VIV energy harvesters is the installation of the cylindrical bluff body at the tip of cantilever beam with different orientations (bottom, top, horizontal, and vertical). Experiments show that the synchronization regions of the bottom, top, and horizontal configurations are almost the same at low wind speeds (around 1.5 m/s). The vertical configuration has the highest wind speed for synchronization (around 3.5 m/s) with the largest harvested power, which is explained by its highest natural frequency and the smallest coupled damping. The results lead to the conclusion that to design efficient VIV energy harvesters, the bluff body should be aligned with the beam for low wind speeds (<2 m/s) and perpendicular to the beam at high wind speeds (>2 m/s)

  11. CFD simulation of flow-induced vibration of an elastically supported airfoil

    Directory of Open Access Journals (Sweden)

    Šidlof Petr

    2016-01-01

    Full Text Available Flow-induced vibration of lifting or control surfaces in aircraft may lead to catastrophic consequences. Under certain circumstances, the interaction between the airflow and the elastic structure may lead to instability with energy transferred from the airflow to the structure and with exponentially increasing amplitudes of the structure. In the current work, a CFD simulation of an elastically supported NACA0015 airfoil with two degrees of freedom (pitch and plunge coupled with 2D incompressible airflow is presented. The geometry of the airfoil, mass, moment of inertia, location of the centroid, linear and torsional stiffness was matched to properties of a physical airfoil model used for wind-tunnel measurements. The simulations were run within the OpenFOAM computational package. The results of the CFD simulations were compared with the experimental data.

  12. A global strategy for the stability analysis of friction induced vibration problem with parameter variations

    Science.gov (United States)

    Do, H. Q.; Massa, F.; Tison, T.; Lallemand, B.

    2017-02-01

    This paper presents a numerical strategy to reanalyze the modified frequency stability analysis of friction induced vibration problem. The stability analysis of a mechanical system relies on several coupling steps, namely a non-linear static analysis followed by linear and complex eigenvalue problems. We thus propose a numerical strategy to perform more rapidly multiple complex eigenvalue analyses. This strategy couples three methods namely, Fuzzy Logic Controllers to manage frictional contact problem, homotopy developments and projection techniques to reanalyze the projection matrices and component mode synthesis to calculate the modified eigensolutions. A numerical application is performed to highlight the efficiency of the strategy and a discussion is proposed in terms of precision and computational time.

  13. Hydrodynamic performance of flexible risers subject to vortex-induced vibrations

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hui; YANG Jian-min; XIAO Long-fei; LU Hai-ning

    2013-01-01

    The Vortex-Induced Vibration (VIV) displacements are determined from both the measured accelerations and strains in a series of VIV experiments.Based on the results,the forces in the longitudinal,transversal and tangential directions are estimated by using the finite element method with and without considering the interactions between adjacent elements.The numerical simulation indicates that the method considering the interactions performs better in the estimation of the forces.The component of the transversal force in phase with the acceleration is associated with the added mass coefficient.The estimated added mass coefficients take abnormally high values at the locations where the displacements are small.An improved formula based on the L'Hospital's rule is pro-posed to deal with this problem.The results show the advantage of this formula in estimating the added mass coefficients at the loca-tions with small ⅥⅤ displacements.

  14. Numerical Prediction of Vortex Induced Vibrations on Top Tensioned Riser in Consideration of Internal Flow

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In consideration of the effect of the internal flowing fluid and the external marine environmental condition on the vortex-induced vibration (VIV) of top tensioned riser (TTR), the differential equation is derived based on work-energy principles and the riser near wake dynamics is modeled by Facchinetti's wake oscillator model. Then Galerkin's finite element approximation is implemented to derive the nonlinear matrix equation of the coupled equations and the corresponding numerical programs are compiled which solve the coupled equations directly in the time domain. The comparison of the predicted results with the recent experimental results and the prediction of SHEAR7 is performed. The results show the validity of the proposed method on the prediction of VIV of deep water risers. The effect of internal flow on the dynamic characteristics and dynamic response of the riser is analyzed and several valuable conclusions are drawn.

  15. On the efficiency of energy harvesting using vortex-induced vibrations of cables

    CERN Document Server

    Grouthier, Clement; Bourguet, Remi; Modarres-Sadeghi, Yahya; de Langre, Emmanuel

    2014-01-01

    Many technologies based on fluid-structure interaction mechanisms are being developed to harvest energy from geophysical flows. The velocity of such flows is low, and so is their energy density. Large systems are therefore required to extract a significant amount of energy. The question of the efficiency of energy harvesting using vortex-induced vibrations (VIV) of cables is addressed in this paper, through two reference configurations: (i) a long tensioned cable with periodically-distributed harvesters and (ii) a hanging cable with a single harvester at its upper extremity. After validation against either direct numerical simulations or experiments, an appropriate reduced-order wake- oscillator model is used to perform parametric studies of the impact of the harvesting parameters on the efficiency. For both configurations, an optimal set of parameters is identified and it is shown that the maximum efficiency is close to the value reached with an elastically-mounted rigid cylinder. The variability of the effi...

  16. Model Test Study on Ice-Induced Vibrations of Compliant Multi-Cone Structures

    Institute of Scientific and Technical Information of China (English)

    HUANG Yan; SHI Qing-zeng; SONG An

    2009-01-01

    For the study on the ice-induced vibration of a compliant mono-cone structure,a series of model tests were performed from 2004 to 2006.In these tests,the ice sheet before the compliant conical structure was found to be failed in two-time breaking.Based on this important finding,model tests study of the ice force on a compliant multi-cone structure were performed from 2006 to 2007.in these tests,the ice sheet broke before each single cone non-simultaneously.The exciting energy of the total ice force was found to be in a wide range of frequencies,and the structure can be easily excited with nonlinear resonance.

  17. Laser-Induced Acoustic Desorption Atmospheric Pressure Photoionization via VUV-Generating Microplasmas

    Science.gov (United States)

    Benham, Kevin; Hodyss, Robert; Fernández, Facundo M.; Orlando, Thomas M.

    2016-11-01

    We demonstrate the first application of laser-induced acoustic desorption (LIAD) and atmospheric pressure photoionization (APPI) as a mass spectrometric method for detecting low-polarity organics. This was accomplished using a Lyman-α (10.2 eV) photon generating microhollow cathode discharge (MHCD) microplasma photon source in conjunction with the addition of a gas-phase molecular dopant. This combination provided a soft desorption and a relatively soft ionization technique. Selected compounds analyzed include α-tocopherol, perylene, cholesterol, phenanthrene, phylloquinone, and squalene. Detectable surface concentrations as low as a few pmol per spot sampled were achievable using test molecules. The combination of LIAD and APPI provided a soft desorption and ionization technique that can allow detection of labile, low-polarity, structurally complex molecules over a wide mass range with minimal fragmentation.

  18. Laser-Induced Acoustic Desorption Atmospheric Pressure Photoionization via VUV-Generating Microplasmas.

    Science.gov (United States)

    Benham, Kevin; Hodyss, Robert; Fernández, Facundo M; Orlando, Thomas M

    2016-11-01

    We demonstrate the first application of laser-induced acoustic desorption (LIAD) and atmospheric pressure photoionization (APPI) as a mass spectrometric method for detecting low-polarity organics. This was accomplished using a Lyman-α (10.2 eV) photon generating microhollow cathode discharge (MHCD) microplasma photon source in conjunction with the addition of a gas-phase molecular dopant. This combination provided a soft desorption and a relatively soft ionization technique. Selected compounds analyzed include α-tocopherol, perylene, cholesterol, phenanthrene, phylloquinone, and squalene. Detectable surface concentrations as low as a few pmol per spot sampled were achievable using test molecules. The combination of LIAD and APPI provided a soft desorption and ionization technique that can allow detection of labile, low-polarity, structurally complex molecules over a wide mass range with minimal fragmentation. Graphical Abstract ᅟ.

  19. Glottal configuration, acoustic, and aerodynamic changes induced by variation in suture direction in arytenoid adduction procedures.

    Science.gov (United States)

    Inagi, Katsuhide; Connor, Nadine P; Suzuki, Tatsutoshi; Ford, Charles N; Bless, Diane M; Nakajima, Masami

    2002-10-01

    Arytenoid adduction is a phonosurgical procedure in which the arytenoid cartilages are approximated to reduce posterior glottal gap size and improve voice. Voice outcomes following arytenoid adduction are not always optimal. The goal of this study was to systematically vary suture direction and force of pull on the arytenoid cartilages in a human excised laryngeal model to determine the optimal combination of factors for reducing glottal gap and improving voice. Several factors demonstrated significant effects. Changes in suture direction and force of pull affected glottal configuration in both the horizontal and vertical planes. Increased force of pull on the muscular process resulted in increased adduction of the vocal process for all suture directions. Changes in suture direction and force of pull also affected acoustic and aerodynamic measures of induced voice. Therefore, voice outcomes can be optimized with arytenoid adduction if the vocal fold plane is accurately adjusted.

  20. The effect of temperature dependent tissue parameters on acoustic radiation force induced displacements

    Science.gov (United States)

    Suomi, Visa; Han, Yang; Konofagou, Elisa; Cleveland, Robin O.

    2016-10-01

    Multiple ultrasound elastography techniques rely on acoustic radiation force (ARF) in monitoring high-intensity focused ultrasound (HIFU) therapy. However, ARF is dependent on tissue attenuation and sound speed, both of which are also known to change with temperature making the therapy monitoring more challenging. Furthermore, the viscoelastic properties of tissue are also temperature dependent, which affects the displacements induced by ARF. The aim of this study is to quantify the temperature dependent changes in the acoustic and viscoelastic properties of liver and investigate their effect on ARF induced displacements by using both experimental methods and simulations. Furthermore, the temperature dependent viscoelastic properties of liver are experimentally measured over a frequency range of 0.1-200 Hz at temperatures reaching 80 °C, and both conventional and fractional Zener models are used to fit the data. The fractional Zener model was found to fit better with the experimental viscoelasticity data with respect to the conventional model with up to two orders of magnitude lower sum of squared errors (SSE). The characteristics of experimental displacement data were also seen in the simulations due to the changes in attenuation coefficient and lesion development. At low temperatures before thermal ablation, attenuation was found to affect the displacement amplitude. At higher temperature, the decrease in displacement amplitude occurs approximately at 60-70 °C due to the combined effect of viscoelasticity changes and lesion growth overpowering the effect of attenuation. The results suggest that it is necessary to monitor displacement continuously during HIFU therapy in order to ascertain when ablation occurs.

  1. A novel wireless and temperature-compensated SAW vibration sensor.

    Science.gov (United States)

    Wang, Wen; Xue, Xufeng; Huang, Yangqing; Liu, Xinlu

    2014-11-03

    A novel wireless and passive surface acoustic wave (SAW) based temperature-compensated vibration sensor utilizing a flexible Y-cut quartz cantilever beam with a relatively substantial proof mass and two one-port resonators is developed. One resonator acts as the sensing device adjacent to the clamped end for maximum strain sensitivity, and the other one is used as the reference located on clamped end for temperature compensation for vibration sensor through the differential approach. Vibration directed to the proof mass flex the cantilever, inducing relative changes in the acoustic propagation characteristics of the SAW travelling along the sensing device, and generated output signal varies in frequency as a function of vibration.  A theoretical mode using the Rayleigh method was established to determine the optimal dimensions of the cantilever beam. Coupling of Modes (COM) model was used to extract the optimal design parameters of the SAW devices prior to fabrication. The performance of the developed SAW sensor attached to an antenna towards applied vibration was evaluated wirelessly by using the precise vibration table, programmable incubator chamber, and reader unit.  High vibration sensitivity of ~10.4 kHz/g, good temperature stability, and excellent linearity were observed in the wireless measurements.

  2. A Novel Wireless and Temperature-Compensated SAW Vibration Sensor

    Directory of Open Access Journals (Sweden)

    Wen Wang

    2014-11-01

    Full Text Available A novel wireless and passive surface acoustic wave (SAW based temperature-compensated vibration sensor utilizing a flexible Y-cut quartz cantilever beam with a relatively substantial proof mass and two one-port resonators is developed. One resonator acts as the sensing device adjacent to the clamped end for maximum strain sensitivity, and the other one is used as the reference located on clamped end for temperature compensation for vibration sensor through the differential approach. Vibration directed to the proof mass flex the cantilever, inducing relative changes in the acoustic propagation characteristics of the SAW travelling along the sensing device, and generated output signal varies in frequency as a function of vibration.  A theoretical mode using the Rayleigh method was established to determine the optimal dimensions of the cantilever beam. Coupling of Modes (COM model was used to extract the optimal design parameters of the SAW devices prior to fabrication. The performance of the developed SAW sensor attached to an antenna towards applied vibration was evaluated wirelessly by using the precise vibration table, programmable incubator chamber, and reader unit.  High vibration sensitivity of ~10.4 kHz/g, good temperature stability, and excellent linearity were observed in the wireless measurements.

  3. Oximetry: a new non-invasive method to detect metabolic effects induced by a local application of mechanical vibration

    Science.gov (United States)

    Felici, A.; Trombetta, C.; Abundo, P.; Foti, C.; Rosato, N.

    2012-10-01

    Mechanical vibrations application is increasingly common in clinical practice due to the effectiveness induced by these stimuli on the human body. Local vibration (LV) application allows to apply and act only where needed, focusing the treatment on the selected body segment. An experimental device for LV application was used to generate the vibrations. The aim of this study was to detect and analyze the metabolic effects induced by LV on the brachial bicep muscle by means of an oximeter. This device monitors tissue and muscle oxygenation using NIRS (Near Infrared Spectroscopy) and is able to determine the concentration of haemoglobin and oxygen saturation in the tissue. In a preliminary stage we also investigated the effects induced by LV application, by measuring blood pressure, heart rate, oxygen saturation and temperature. These data confirmed that the effects induced by LV application are actually localized. The results of the measurements obtained using the oximeter during the vibration application, have shown a variation of the concentrations. In particular an increase of oxygenate haemoglobin was shown, probably caused by an increased muscle activity and/or a rise in local temperature detected during the application.

  4. Active-passive gradient shielding for MRI acoustic noise reduction.

    Science.gov (United States)

    Edelstein, William A; Kidane, Tesfaye K; Taracila, Victor; Baig, Tanvir N; Eagan, Timothy P; Cheng, Yu-Chung N; Brown, Robert W; Mallick, John A

    2005-05-01

    An important source of MRI acoustic noise-magnet cryostat warm-bore vibrations caused by eddy-current-induced forces-can be mitigated by a passive metal shield mounted on the outside of a vibration-isolated, vacuum-enclosed shielded gradient set. Finite-element (FE) calculations for a z-gradient indicate that a 2-mm-thick Cu layer wrapped on the gradient assembly can decrease mechanical power deposition in the warm bore and reduce warm-bore acoustic noise production by about 25 dB. Eliminating the conducting warm bore and other magnet parts as significant acoustic noise sources could lead to the development of truly quiet, fully functioning MRI systems with noise levels below 70 dB.

  5. A numerical study of microparticle acoustophoresis driven by acoustic radiation forces and streaming-induced drag forces

    DEFF Research Database (Denmark)

    Muller, Peter Barkholt; Barnkob, Rune; Jensen, Mads Jakob Herring;

    2012-01-01

    We present a numerical study of the transient acoustophoretic motion of microparticles suspended in a liquid-filled microchannel and driven by the acoustic forces arising from an imposed standing ultrasound wave: the acoustic radiation force from the scattering of sound waves on the particles...... parameters using a numerical particle-tracking scheme. The model shows the transition in the acoustophoretic particle motion from being dominated by streaming-induced drag to being dominated by radiation forces as a function of particle size, channel geometry, and material properties....

  6. Amplitude control of the track-induced self-excited vibration for a maglev system.

    Science.gov (United States)

    Zhou, Danfeng; Li, Jie; Zhang, Kun

    2014-09-01

    The Electromagnet Suspension (EMS) maglev train uses controlled electromagnetic forces to achieve suspension, and self-excited vibration may occur due to the flexibility of the track. In this article, the harmonic balance method is applied to investigate the amplitude of the self-excited vibration, and it is found that the amplitude of the vibration depends on the voltage of the power supplier. Based on this observation, a vibration amplitude control method, which controls the amplitude of the vibration by adjusting the voltage of the power supplier, is proposed to attenuate the vibration. A PI controller is designed to control the amplitude of the vibration at a given level. The effectiveness of this method shows a good prospect for its application to commercial maglev systems.

  7. Cannabinoid CB1 receptor agonists do not decrease, but may increase, acoustic trauma-induced tinnitus in rats

    Directory of Open Access Journals (Sweden)

    Yiwen eZheng

    2015-03-01

    Full Text Available Tinnitus has been suggested to arise from neuronal hyperactivity in auditory areas of the brain and anti-epileptic drugs are sometimes used to provide relief from tinnitus. Recently, the anti-epileptic properties of the cannabinoid drugs have gained increasing interest; however, the use of cannabinoids as a form of treatment for tinnitus is controversial. In the present study, we tested whether a combination of delta-9-tetrahydrocannabinol (delta-9-THC and cannabidiol (CBD, delivered in a 1:1 ratio, could affect tinnitus perception in a rat model of acoustic trauma-induced tinnitus. Following sham treatment or acoustic trauma, the animals were divided into the following groups: 1 sham (i.e. no acoustic trauma with vehicle treatment; 2 sham with drug treatment (i.e. delta-9-THC + CBD; 3 acoustic trauma-exposed exhibiting tinnitus, with drug treatment; and 4 acoustic trauma-exposed exhibiting no tinnitus, with drug treatment. The animals received either the vehicle or the cannabinoid drugs every day, 30 min before the tinnitus behavioural testing. Acoustic trauma caused a significant increase in the auditory brainstem response (ABR thresholds in the exposed animals, indicating hearing loss; however, there was a partial recovery over 6 months. Acoustic trauma did not always result in tinnitus; however among those that did exhibit tinnitus, some of them had tinnitus at multiple frequencies while others had it only at a single frequency. The cannabinoids significantly increased the number of tinnitus animals in the exposed-tinnitus group, but not in the sham group. The results suggest that cannabinoids may promote the development of tinnitus, especially when there is pre-existing hearing damage.

  8. Experimental study and finite element analysis of wind-induced vibration of modal car based on fluid-structure interaction

    Institute of Scientific and Technical Information of China (English)

    TAO Li-li; DU Guang-sheng; LIU Li-ping; LIU Yong-hui; SHAO Zhu-feng

    2013-01-01

    The wind-induced vibration of the front windshield concerns the traffic safety and the aerodynamic charactefistcs of cars.In this paper,the numerical simulation and the experiment are combined to study the wind-induced vibrations of the front windshield at different speeds of a van-body model bus.The Fluid-Structure Interaction (FSI) model is used for the finite element analysis of the vibration characteristics of the front windshield glass in the travelling process,and the wind-induced vibration response characteristics of the glass is obtained.A wind-tunnel experiment with an eddy current displacement sensor is carried out to study the deformation of the windshield at different wind speeds,and to verify the numerical simulation results.It is shown that the windshield of the model bus windshield undergoes a noticeable deformation as the speed changes,and from the deformation curve obtained,it is seen that in the accelerating process,the deformation of the glass increases as the speed increases,and with the speed being stablized,it also tends to a certain value.The results of this study can provide a scientific basis for the safety design of the windshield and the body.

  9. Perception of acoustically complex phonological features in vowels is reflected in the induced brain-magnetic activity

    Directory of Open Access Journals (Sweden)

    Obleser Jonas

    2007-06-01

    Full Text Available Abstract A central issue in speech recognition is which basic units of speech are extracted by the auditory system and used for lexical access. One suggestion is that complex acoustic-phonetic information is mapped onto abstract phonological representations of speech and that a finite set of phonological features is used to guide speech perception. Previous studies analyzing the N1m component of the auditory evoked field have shown that this holds for the acoustically simple feature place of articulation. Brain magnetic correlates indexing the extraction of acoustically more complex features, such as lip rounding (ROUND in vowels, have not been unraveled yet. The present study uses magnetoencephalography (MEG to describe the spatial-temporal neural dynamics underlying the extraction of phonological features. We examined the induced electromagnetic brain response to German vowels and found the event-related desynchronization in the upper beta-band to be prolonged for those vowels that exhibit the lip rounding feature (ROUND. It was the presence of that feature rather than circumscribed single acoustic parameters, such as their formant frequencies, which explained the differences between the experimental conditions. We conclude that the prolonged event-related desynchronization in the upper beta-band correlates with the computational effort for the extraction of acoustically complex phonological features from the speech signal. The results provide an additional biomagnetic parameter to study mechanisms of speech perception.

  10. A direct pedestrian-structure interaction model to characterize the human induced vibrations on slender footbridges

    Directory of Open Access Journals (Sweden)

    Jiménez-Alonso, J. F.

    2014-12-01

    Full Text Available Although the scientific community had knowledge of the human induced vibration problems in structures since the end of the 19th century, it was not until the occurrence of the vibration phenomenon happened in the Millennium Bridge (London, 2000 that the importance of the problem revealed and a higher level of attention devoted. Despite the large advances achieved in the determination of the human-structure interaction force, one of the main deficiencies of the existing models is the exclusion of the effect of changes in the footbridge dynamic properties due to the presence of pedestrians. In this paper, the formulation of a human-structure interaction model, addresses these limitations, is carried out and its reliability is verified from previously published experimental results.Aunque la comunidad científica tenía conocimiento de los problemas vibratorios inducidos por peatones en estructuras desde finales del siglo xix, no fue hasta la ocurrencia de los eventos vibratorios acontecidos en la pasarela del Milenio (Londres, 2000, cuando la importancia del problema se puso de manifiesto y se le comenzó a dedicar un mayor nivel de atención. A pesar de los grandes avances alcanzados en la caracterización de la fuerza de interacción peatón-estructura una de las principales deficiencias de los modelos existentes es la exclusión del cambio en las propiedades dinámicas de la pasarela por la presencia de peatones. En este artículo, se presenta la formulación de un modelo de interacción peatón-estructura que intenta dar respuesta a dichas limitaciones, y su validación a partir de resultados experimentales previamente publicados por otros autores.

  11. Acoustically induced spin transport in (110)GaAs quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Couto, Odilon D.D. Jr.

    2008-09-29

    In this work, we employ surface acoustic waves (SAWs) to transport and manipulate optically generated spin ensembles in (110) GaAs quantum wells (QWs). The strong carrier confinement into the SAW piezoelectric potential allows for the transport of spin-polarized carrier packets along well-defined channels with the propagation velocity of the acoustic wave. In this way, spin transport over distances exceeding 60 m is achieved, corresponding to spin lifetimes longer than 20 ns. The demonstration of such extremely long spin lifetimes is enabled by three main factors: (i) Suppression of the D'yakonov-Perel' spin relaxation mechanism for z-oriented spins in (110) IIIV QWs; (ii) Suppression of the Bir-Aronov-Pikus spin relaxation mechanism caused by the type-II SAW piezoelectric potential; (iii) Suppression of spin relaxation induced by the mesoscopic carrier confinement into narrow stripes along the SAW wave front direction. A spin transport anisotropy under external magnetic fields (B{sub ext}) is demonstrated for the first time. Employing the well-defined average carrier momentum impinged by the SAW, we analyze the spin dephasing dynamics during transport along the [001] and [1 anti 10] in-plane directions. For transport along [001], fluctuations of the internal magnetic field (B{sub int}), which arises from the spin-orbit interaction associated with the bulk inversion asymmetry of the crystal, lead to decoherence within 2 ns as the spins precess around B{sub ext}. In contrast, for transport along the [1 anti 10] direction, the z-component of the spin polarization is maintained for times one order of magnitude longer due to the non-zero average value of B{sub int}. The dephasing anisotropy between the two directions is fully understood in terms of the dependence of the spin-orbit coupling on carrier momentum direction, as predicted by the D'yakonov-Perel' mechanism for the (110) system. (orig.)

  12. Image Processing for Capturing Motions of Crowd and Its Application to Pedestrian-Induced Lateral Vibration of a Footbridge

    Directory of Open Access Journals (Sweden)

    Junji Yoshida

    2007-01-01

    Full Text Available An image processing technique to capture motions of crowds is proposed and it is applied to understanding pedestrian-induced lateral vibration in a footbridge. Firstly, an outline of recording sequential images of vibration in the bridge is described and, then an image processing for human-head recognition from a single image of crowd is developed. In this method, conventional template matching techniques with human-head templates are extended by employing some selected templates, an updated search-algorithm and a classifier for clustering. Consequently, more than 50% of human-heads could be identified by the proposed method. Then, motions of detected human-heads, together with the bridge response, are tracked. Finally, interaction between the motions of pedestrians and the vibration of the bridge is discussed, with the emphasis on synchronization between the responses of the pedestrians and the bridge.

  13. Understanding and controlling wind-induced vibrations of bridge cables: Results from the Femern Crossing research project

    DEFF Research Database (Denmark)

    Georgakis, Christos T.; Jakobsen, J. B.; Koss, Holger;

    behind the cable vibrations that were observed on the cable-supported bridges forming part of the aforementioned crossings, Femern A/S commissioned a 5-year international collaborative research project, entitled “Understanding and controlling wind-induced vibrations of bridge cables”. The ultimate goal...... of the project has been the establishment of novel vibration mitigation schemes that could be readily, economically, and effectively implemented on a cable-supported bridge that might form part of the fixed link. In support of the proposed research, Femern A/S commissioned a new climatic wind tunnel, designed...... specifically for the testing of bridge cables. Five years after its initiation, the participants report the main results from the research project....

  14. Whole body vibration induces forepaw and hind paw behavioral sensitivity in the rat.

    Science.gov (United States)

    Baig, Hassam A; Guarino, Benjamin B; Lipschutz, Daniel; Winkelstein, Beth A

    2013-11-01

    Whole body vibration (WBV) has been linked to neck and back pain, but the biomechanical and physiological mechanisms responsible for its development and maintenance are unknown. A rodent model of WBV was developed in which rats were exposed to different WBV paradigms, either daily for 7 consecutive days (repeated WBV) or two single exposures at Day 0 and 7 (intermittent WBV). Each WBV session lasted for 30 min and was imposed at a frequency of 15 Hz and RMS platform acceleration of 0.56 ± 0.07 g. Changes in the withdrawal response of the forepaw and hind paw were measured, and were used to characterize the onset and maintenance of behavioral sensitivity. Accelerations and displacements of the rat and deformations in the cervical and lumbar spines were measured during WBV to provide mechanical context for the exposures. A decrease in withdrawal threshold was induced at 1 day after the first exposure in both the hind paw and forepaw. Repeated WBV exhibited a sustained reduction in withdrawal threshold in both paws and intermittent WBV induced a sustained response only in the forepaw. Cervical deformations were significantly elevated which may explain the more robust forepaw response. Findings suggest that a WBV exposure leads to behavioral sensitivity.

  15. Wind- and Rain-Induced Vibrations Impose Different Selection Pressures on Multimodal Signaling.

    Science.gov (United States)

    Halfwerk, Wouter; Ryan, Michael J; Wilson, Preston S

    2016-09-01

    The world is a noisy place, and animals have evolved a myriad of strategies to communicate in it. Animal communication signals are, however, often multimodal; their components can be processed by multiple sensory systems, and noise can thus affect signal components across different modalities. We studied the effect of environmental noise on multimodal communication in the túngara frog (Physalaemus pustulosus). Males communicate with rivals using airborne sounds combined with call-induced water ripples. We tested males under control as well as noisy conditions in which we mimicked rain- and wind-induced vibrations on the water surface. Males responded more strongly to a multimodal playback in which sound and ripples were combined, compared to a unimodal sound-only playback, but only in the absence of rain and wind. Under windy conditions, males decreased their response to the multimodal playback, suggesting that wind noise interferes with the detection of rival ripples. Under rainy conditions, males increased their response, irrespective of signal playback, suggesting that different noise sources can have different impacts on communication. Our findings show that noise in an additional sensory channel can affect multimodal signal perception and thereby drive signal evolution, but not always in the expected direction.

  16. Investigations on the Effects of Vortex-Induced Vibration with Different Distributions of Lorentz Forces

    Directory of Open Access Journals (Sweden)

    Hui Zhang

    2017-01-01

    Full Text Available The control of vortex-induced vibration (VIV in shear flow with different distributions of Lorentz force is numerically investigated based on the stream function–vorticity equations in the exponential-polar coordinates exerted on moving cylinder for Re = 150. The cylinder motion equation coupled with the fluid, including the mathematical expressions of the lift force coefficient C l , is derived. The initial and boundary conditions as well as the hydrodynamic forces on the surface of cylinder are also formulated. The Lorentz force applied to suppress the VIV has no relationship with the flow field, and involves two categories, i.e., the field Lorentz force and the wall Lorentz force. With the application of symmetrical Lorentz forces, the symmetric field Lorentz force can amplify the drag, suppress the flow separation, decrease the lift fluctuation, and then suppress the VIV while the wall Lorentz force decreases the drag only. With the application of asymmetrical Lorentz forces, besides the above-mentioned effects, the field Lorentz force can increase additional lift induced by shear flow, whereas the wall Lorentz force can counteract the additional lift, which is dominated on the total effect.

  17. Modeling and simulation of vortex induced vibration on the subsea riser/pipeline (GRP pipe)

    Science.gov (United States)

    Raja Adli, Raja Nor Fauziah bt; Ibrahim, Idris

    2012-06-01

    This paper presents the research work conducted to investigate the dynamics characteristics of the offshore riser pipeline due to vortex flow and to develop a model that could predict its vortex induced responses. Glass-fiber reinforced plastic (GRP) pipe is used for this study which has smaller density from the steel. A two-dimensional finite element computational method is implemented to describe the dynamic behavior of the riser. The governing equation of motion was based on Hamilton's principle, consists of the strain energy due to bending and axial deformation, kinetic energy due to both riser and internal fluid movement and also external force from currents and waves. A direct integration method namely Newmark integration scheme is proposed to solve the equation of motion. A MATLAB program code was developed to obtain the simulation results. The natural frequency and damping ratio are presented for each mode. Dynamic response of riser is shown in time-domain and the numerical results are discussed. Several parameter effects are used to investigate dynamic responses and the results show an agreement with the theory. Vortex shedding phenomenon also has been discussed in this paper. As a conclusion, the simulation results have successfully shown the vortex induced vibration responses for GRP pipeline.

  18. Pseudo-Spectrum Time Domain and Time Reversal Mirror technique using in Microwave-induced Thermo-Acoustic Tomography System

    Directory of Open Access Journals (Sweden)

    Guoping Chen

    2011-06-01

    Full Text Available Microwave-Induced Thermo-Acoustic Tomograp- phy (MITAT has attracted more concerns in recent years in biomedical imaging field. It has both the high contrast of the microwave imaging and the high resolution of ultrasound imaging. As compared to optoacoustics, which uses instead a pulsed light for evoking optoacoustic response, thermo-aco- ustic imaging has the advantage of deeper tissue penetration, attaining the potential for wider clinical dissemination, especially for malignant tumors. In this paper, the induced thermo-acoustic wave propagating in a mimic biologic tissue is simulated by numeric method Pseudo-Spectrum Time Domain (PSTD. Due to the excellent performance in noise- depress and the stability for the fluctuation of the model parameters, Time Reversal Mirror (TRM imaging technique is studied computationally for the simulative received therm- o-acoustic signals. Some thermo-acoustic objects with differ- ent initial pressure distribution are designed and imaged by TRM technique to represent the complex biologic tissue case in a random media. The quality of images generated by TRM technique based on PSTD method hints the potential of the MITAT technique.

  19. Evaluation of acoustic shock induced early hearing loss with audiometer and distortion product otoacoustic emissions

    OpenAIRE

    2010-01-01

    Background: Acoustic shock injury has been described as a permanent injury to the auditory system either due to daily noise dose of in excess of 85 decibels or very loud impulse sound reputed to be in excess of 120 decibels and acoustic incidents. This study was performed to compare the results of audiogram and the newer diagnostic method distortion product otoacoustic emissions (DPOAEs) parameters due to acoustic shock injury in call center professionals working in a noisy environment and pr...

  20. Clinical interest of postural and vestibulo-ocular reflex changes induced by cervical muscles and skull vibration in compensated unilateral vestibular lesion patients.

    Science.gov (United States)

    Dumas, Georges; Lion, Alexis; Gauchard, Gérome C; Herpin, Guillaume; Magnusson, Måns; Perrin, Philippe P

    2013-01-01

    Skull vibration induces nystagmus in unilateral vestibular lesion (UVL) patients. Vibration of skull, posterior cervical muscles or inferior limb muscles alters posture in recent UVL patients. This study aimed to investigate the postural effect of vibration in chronic compensated UVL patients. Vibration was applied successively to vertex, each mastoid, each side of posterior cervical muscles and of triceps surae in 12 UVL patients and 9 healthy subjects. Eye movements were recorded with videonystagmography. Postural control was evaluated in eyes open (EO) and eyes closed (EC) conditions. Sway area, sway path, anteroposterior and medio-lateral sways were recorded.A vibration induced nystagmus (VIN) beating toward the healthy side was obtained for each UVL patient during mastoid vibration. In EO, only sway path was higher in UVL group during vibration of mastoids and posterior cervical muscles.The EO postural impairments of UVL patients could be related to the eye movements or VIN, leading to visual perturbations, or to a proprioceptive error signal, providing an erroneous representation of head position. The vibration-induced sway was too small to be clinically useful. Vestibulo-ocular reflex observed with videonystagmography during mastoid vibration seems more relevant to reveal chronic UVL than vestibulo-spinal reflex observed with posturography.

  1. 湍流进流诱发的二维水翼振动噪声特性研究%Study on the 2D Hydrofoil Vibration and Noise Induced by Ingested Turbulence

    Institute of Scientific and Technical Information of China (English)

    范国栋; 谌勇; 华宏星

    2015-01-01

    为研究螺旋桨流噪声,以螺旋桨的基本构型单位二维翼型为研究对象,研究其在不同工况下的振动噪声规律。以Lighthill声类比理论为基础,应用计算流体力学软件CFX和声学仿真软件LMS Virtual Lab分别模拟在不同工况下翼型的流场和声场分布。取翼型非定常脉动力作为声源,然后采用边界元方法分别求解翼型流噪声和振动噪声。结果表明,噪声水平随速度和翼型攻角的变化呈现较为明显的规律;相比考虑翼型振动时的振动噪声,忽略翼型振动影响的情况下流噪声水平偏大。%In order to study the flow noise of propellers, the rules of vibration and sound radiation of a 2D hydrofoil, which is the basic composition unit of the propeller, were investigated in different working conditions. Based on Lighthill’s acoustics analogy, the flow field and acoustic field of the hydrofoil were simulated by means of the computational fluid dynamics software CFX and the acoustic software LMS Virtual Lab. Taking the unsteady fluctuating pressure induced by the fluid on the hydrofoil as the noise source, the boundary element method (BEM) was used to compute the flow noise and the vibration noise of the hydrofoil. The results show that the sound pressure change of the noise has distinct rules with the velocity and the incidence angle change. The sound level of the flow noise neglecting the influence of the hydrofoil vibration is higher than that of considering the influence of the vibration noise.

  2. Acoustic module of the Acquabona (Italy debris flow monitoring system

    Directory of Open Access Journals (Sweden)

    A. Galgaro

    2005-01-01

    Full Text Available Monitoring of debris flows aimed to the assessment of their physical parameters is very important both for theoretical and practical purposes. Peak discharge and total volume of debris flows are crucial for designing effective countermeasures in many populated mountain areas where losses of lives and property damage could be avoided. This study quantifies the relationship between flow depth, acoustic amplitude of debris flow induced ground vibrations and front velocity in the experimental catchment of Acquabona, Eastern Dolomites, Italy. The analysis of data brought about the results described in the following. Debris flow depth and amplitude of the flow-induced ground vibrations show a good positive correlation. Estimation of both mean front velocity and peak discharge can be simply obtained monitoring the ground vibrations, through geophones installed close to the flow channel; the total volume of debris flow can be so directly estimated from the integral of the ground vibrations using a regression line. The application of acoustic technique to debris flow monitoring seems to be of the outmost relevance in risk reduction policies and in the correct management of the territory. Moreover this estimation is possible in other catchments producing debris flows of similar characteristics by means of their acoustic characterisation through quick and simple field tests (Standard Penetration Tests and seismic refraction surveys.

  3. Laser Imaging of Airborne Acoustic Emission by Nonlinear Defects

    Science.gov (United States)

    Solodov, Igor; Döring, Daniel; Busse, Gerd

    2008-06-01

    Strongly nonlinear vibrations of near-surface fractured defects driven by an elastic wave radiate acoustic energy into adjacent air in a wide frequency range. The variations of pressure in the emitted airborne waves change the refractive index of air thus providing an acoustooptic interaction with a collimated laser beam. Such an air-coupled vibrometry (ACV) is proposed for detecting and imaging of acoustic radiation of nonlinear spectral components by cracked defects. The photoelastic relation in air is used to derive induced phase modulation of laser light in the heterodyne interferometer setup. The sensitivity of the scanning ACV to different spatial components of the acoustic radiation is analyzed. The animated airborne emission patterns are visualized for the higher harmonic and frequency mixing fields radiated by planar defects. The results confirm a high localization of the nonlinear acoustic emission around the defects and complicated directivity patterns appreciably different from those observed for fundamental frequencies.

  4. Prediction and validation of high frequency vibration repsonses of NASA Mars Pathfinder spacecraft due to acoustic launch load using statistical energy analysis

    Science.gov (United States)

    Hwang, H. J.

    2002-01-01

    Mid and high frequency structural responses of a spacecraft during the launch condition are mainly dominated by the intense acoustic pressure field over the exterior of the launch vehicle. The prediction of structural responses due to the acoustic launch load is therefore an important analysis for engineers and scientists to correctly define various dynamics specifications of the spacecraft.

  5. Discussion of "A new method for predicting nonlinear structural vibrations induced by ground impact loading" by Jun Liu, Yu Zhang, Bin Yun, Journal of Sound and Vibration, 331 (2012) 2129-2140

    Science.gov (United States)

    Svinkin, Mark R.

    2016-12-01

    The authors suggested a hybrid method for modeling the time history of structural vibrations triggered by impact dynamic loads from construction equipment and blasting, and they stated, "In this work, a hybrid method has been proposed to calculate the theoretical seismograms of structural vibrations. The word "hybrid" denotes a combination of field measurements and computer simulations. Then, based on nonlinear system theory, a novel method is proposed to predict the signal induced by impact loading".

  6. Vibration perception and thermoperception as quantitative measurements in the monitoring of cisplatin induced neurotoxicity

    NARCIS (Netherlands)

    Gispen, W.H.; Elderson, Arthur; Gerritsen van der Hoop, R.; Haanstra, W.; Neijt, J.P.; Jennekens, F.G.I.

    1989-01-01

    In 20 ovarian cancer patients treated by cisplatin-based chemotherapy quantitative investigations of the vibration and the thermoperception were performed. Following the administration of cisplatin of 300 mg/m2 and more the vibration perception threshold (VPT) was shown to be significantly elevated

  7. Frequencies in the Vibration Induced by the Rotor Stator Interaction in a Centrifugal Pump Turbine

    DEFF Research Database (Denmark)

    Rodriguez, Cristian; Egusquiza, Eduard; Santos, Ilmar

    2007-01-01

    The highest vibration levels in large pump turbines are, in general, originated in the rotor stator interaction (RSI). This vibration has specific characteristics that can be clearly observed in the frequency domain: harmonics of the moving blade passing frequency and a particular relationship am...

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

    DEFF Research Database (Denmark)

    Acampora, Antonio; Georgakis, Christos

    2011-01-01

    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...

  9. Investigation on flow and mixing characteristics of supersonic mixing layer induced by forced vibration of cantilever

    Science.gov (United States)

    Zhang, Dongdong; Tan, Jianguo; Lv, Liang

    2015-12-01

    The mixing process has been an important issue for the design of supersonic combustion ramjet engine, and the mixing efficiency plays a crucial role in the improvement of the combustion efficiency. In the present study, nanoparticle-based planar laser scattering (NPLS), particle image velocimetry (PIV) and large eddy simulation (LES) are employed to investigate the flow and mixing characteristics of supersonic mixing layer under different forced vibration conditions. The indexes of fractal dimension, mixing layer thickness, momentum thickness and scalar mixing level are applied to describe the mixing process. Results show that different from the development and evolution of supersonic mixing layer without vibration, the flow under forced vibration is more likely to present the characteristics of three-dimensionality. The laminar flow region of mixing layer under forced vibration is greatly shortened and the scales of rolled up Kelvin-Helmholtz vortices become larger, which promote the mixing process remarkably. The fractal dimension distribution reveals that comparing with the flow without vibration, the turbulent fluctuation of supersonic mixing layer under forced vibration is more intense. Besides, the distribution of mixing layer thickness, momentum thickness and scalar mixing level are strongly influenced by forced vibration. Especially, when the forcing frequency is 4000 Hz, the mixing layer thickness and momentum thickness are 0.0391 m and 0.0222 m at the far field of 0.16 m, 83% and 131% higher than that without vibration at the same position, respectively.

  10. Vibro-acoustical instabilities induced by combustion dynamics in gas turbine combustors

    NARCIS (Netherlands)

    Pozarlik, Artur

    2010-01-01

    The lean premixed combustion suffers from a high sensitivity to thermo-acoustic instabilities which may occur in a combustion chamber of a gas turbine. The high level of acoustic excitation is hazardous to the combustion chamber walls (liner). The situation is even worse when mutual interaction betw

  11. Laser-induced acoustic landmine detection with experimental results on buried landmines

    NARCIS (Netherlands)

    Heuvel, J.C. van den; Putten, F.J.M. van; Koersel, A.C. van; Schleijpen, H.M.A.

    2004-01-01

    Acoustic landmine detection (ALD) is a technique for the detection of buried landmines including non-metal mines. Since it gives complementary results with GPR or metal detection, sensor fusion of these techniques with acoustic detection would give promising results. Two methods are used for the aco

  12. Evaluation of acoustic shock induced early hearing loss with audiometer and distortion product otoacoustic emissions

    Directory of Open Access Journals (Sweden)

    R S Vinodh

    2010-01-01

    Full Text Available Background: Acoustic shock injury has been described as a permanent injury to the auditory system either due to daily noise dose of in excess of 85 decibels or very loud impulse sound reputed to be in excess of 120 decibels and acoustic incidents. This study was performed to compare the results of audiogram and the newer diagnostic method distortion product otoacoustic emissions (DPOAEs parameters due to acoustic shock injury in call center professionals working in a noisy environment and prone to acoustic injury. Materials and Methods: Hearing functions of 340 subjects were first assessed with pure tone audiometry and then DPOAEs results were compared among acoustic shock exposed subjects with normal audiogram and those with abnormal audiogram. Results: Out of 340 acoustic shock exposed subjects 304 were normal on audiometric testing and 34 had abnormal audiograms. Subsequently on DPOAE testing out of 304 acoustic shock exposed subjects with normal audiogram 125 failed and 181 passed. Conclusions: This study showed that DPOAEs are more sensitive than audiometry to detect pre-symptomatic inner ear damage. It may play a role as screening and monitoring test for acoustic shock-exposed workers.

  13. Measurements of shock-induced guided and surface acoustic waves along boreholes in poroelastic materials

    NARCIS (Netherlands)

    Chao, G.; Smeulders, D.M.J.; Van Dongen, M.E.H.

    2006-01-01

    Acoustic experiments on the propagation of guided waves along water-filled boreholes in water-saturated porous materials are reported. The experiments were conducted using a shock tube technique. An acoustic funnel structure was placed inside the tube just above the sample in order to enhance the ex

  14. Microbial-Induced Heterogeneity in the Acoustic Properties of Porous Media

    Science.gov (United States)

    Acoustic wave data were acquired over a two-dimensional region of a microbial-stimulated sand column and an unstimulated sand column to assess the spatiotemporal changes in a porous medium caused by microbial growth and biofilm formation. The acoustic signals from the unstimulate...

  15. Predicting wind-induced vibrations of high-rise buildings using unsteady CFD and modal analysis

    KAUST Repository

    Zhang, Yue

    2015-01-01

    This paper investigates the wind-induced vibration of the CAARC standard tall building model, via unsteady Computational Fluid Dynamics (CFD) and a structural modal analysis. In this numerical procedure, the natural unsteady wind in the atmospheric boundary layer is modeled with an artificial inflow turbulence generation method. Then, the turbulent flow is simulated by the second mode of a Zonal Detached-Eddy Simulation, and a conservative quadrature-projection scheme is adopted to transfer unsteady loads from fluid to structural nodes. The aerodynamic damping that represents the fluid-structure interaction mechanism is determined by empirical functions extracted from wind tunnel experiments. Eventually, the flow solutions and the structural responses in terms of mean and root mean square quantities are compared with experimental measurements, over a wide range of reduced velocities. The significance of turbulent inflow conditions and aeroelastic effects is highlighted. The current methodology provides predictions of good accuracy and can be considered as a preliminary design tool to evaluate the unsteady wind effects on tall buildings.

  16. Vortex-Induced Vibrations of a Square Cylinder with Damped Free-End Conditions

    Directory of Open Access Journals (Sweden)

    S. Manzoor

    2013-01-01

    Full Text Available The authors report the results of vortex-induced vibrations of a square cylinder in a wind tunnel. This constitutes a high mass ratio environment. The square cylinder is mounted in the wind tunnel in such a fashion that it only performs rigid body oscillations perpendicular to the flow direction with damped free-end conditions. This physical situation allows a direct evaluation for analytical models relying on simplified 2D assumptions. The results are also compared with two-dimensional fluid-structure (CFD-CSD numerical simulations. The comparison shows that despite having one-dimensional motion, the analytical model does not predict the VIV region with correctness. Results show that the numerical simulations and experimental results differ from the analytical model for the prediction of reduced velocity corresponding to peak amplitude. Also the analytical reduced velocity envelope is underpredicted compared to both numerical simulations and experimental data despite the structure being lightly damped. The findings are significant as the experimental results for freely oscillating high mass ratio body show differences from the low mass ratio especially in the transition between VIV and galloping regions. However the numerical simulations show comparatively close agreement.

  17. Experimental investigation on vortex-induced vibration of steel catenary riser

    Science.gov (United States)

    Fan, Yu-ting; Mao, Hai-ying; Guo, Hai-yan; Liu, Qing-hai; Li, Xiao-min

    2015-10-01

    Steel catenary riser (SCR) is the transmission device between the seabed and the floating production facilities. As developments move into deeper water, the fatigue life of the riser can become critical to the whole production system, especially due to the vortex-induced vibration (VIV), which is the key factor to operational longevity. As a result, experimental investigation about VIV of the riser was performed in a large plane pool which is 60 m long, 36 m wide and 6.5 m deep. Experiments were developed to study the influence of current speed and seabed on VIV of SCR. The results show that amplitudes of strain and response frequencies increase with the current speed both in cross-flow (CF) and in-line (IL). When the current speed is high, multi-mode response is observed in the VIV motion. The amplitudes of strain in IL direction are not much smaller than those in CF direction. The seabed has influence on the response frequencies of riser and the positions of damage for riser.

  18. Tension and drag forces of flexible risers undergoing vortex-induced vibration

    Science.gov (United States)

    Song, Lei-jian; Fu, Shi-xiao; Li, Man; Gao, Yun; Ma, Lei-xin

    2017-03-01

    This paper presents the results of an experimental investigation on the variation in the tension and the distribution of drag force coefficients along flexible risers under vortex-induced vibration (VIV) in a uniform flow for Reynolds numbers ( Re) up to 2.2×105. The results show that the mean tension is proportional to the square of the incoming current speed, and the tension coefficient of a flexible riser undergoing VIV can be up to 12. The mean drag force is uniformly and symmetrically distributed along the axes of the risers undergoing VIV. The corresponding drag coefficient can vary between 1.6 and 2.4 but is not a constant value of 1.2, as it is for a fixed cylinder in the absence of VIV. These experimental results are used to develop a new empirical prediction model to estimate the drag force coefficient for flexible risers undergoing VIV for Reynolds number on the order of 105, which accounts for the effects of the incoming current speed, the VIV dominant modal number and the frequency.

  19. Simplified Prediction Model for Vortex-Induced Vibrations of Top Tensioned Risers

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    According to the characteristics of deepwater top tensioned risers, a simplified model is presented to predict the multi-modal response of vortex-induced vibration (VIV) in non-uniform flow based on energy equilibrium theory and the experimental data from VIV self-excited and forced oscillations of rigid cylinders. The response amplitude of each mode is determined by a balance between the energy fed into the riser over the lock-in regions and the energy dissipated by the fluid damping over the remainders. Compared with the previous prediction models, this method can take fully account of the intrinsic nature of VIV for low mass ratio structures on lock-in regions, added mass and nonlinear fluid damping effect, etc. Moreover, it is the first time to propose the accurate calculating procedure for VIV amplitude correction factor by solving energy equilibrium equation and a closed form solution is presented for the case of a riser of uniform mass and cross-section oscillating in a uniform flow. The predicted values show a reasonable agreement with VIV experiments of riser models in stepped and sheared currents.

  20. Stress wave propagation analysis on vortex-induced vibration of marine risers

    Science.gov (United States)

    Li, Hua-jun; Wang, Chao; Liu, Fu-shun; Hu, Sau-Lon James

    2017-03-01

    To analyze the stress wave propagation associated with the vortex-induced vibration (VIV) of a marine riser, this paper employed a multi-signal complex exponential method. This method is an extension of the classical Prony's method which decomposes a complicated signal into a number of complex exponential components. Because the proposed method processes multiple signals simultaneously, it can estimate the "global" dominating frequencies (poles) shared by those signals. The complex amplitude (residues) corresponding to the estimated frequencies for those signals is also obtained in the process. As the signals were collected at different locations along the axial direction of a marine riser, the phenomena of the stress wave propagation could be analyzed through the obtained residues of those signals. The Norwegian Deepwater Program (NDP) high mode test data were utilized in the numerical studies, including data sets in both the in-line (IL) and cross-flow (CF) directions. It was found that the most dominant component in the IL direction has its stress wave propagation along the riser being dominated by a standing wave, while that in the CF direction dominated by a traveling wave.