Acoustic streaming theory, applied to micro-scale pumps is presented. A mathematical model based on streaming equations and Mason’s model [9] of the piezoelectric transducer is described. Using this model, the effect of geometric scaling, frequency variation, and excitation amplitude on head and flow rate are examined. The significance of high body forces in the AC boundary layer are demonstrated, along with their effect on mass flow rates for small geometries. It is shown that flow velocities are inversely proportional to the flow tube diameter for small sizes. Experimental data for a macro-scale pump is provided and used to corroborate the static head versus excitation relationship predicted by the model. Compression wave acoustic streaming pumps are shown to have potential viability for micro-scale applications.
{"title":"Micro-Scale Acoustic Streaming Pump Performance Characteristics","authors":"S. Martin, K. Frampton","doi":"10.1115/imece2000-1601","DOIUrl":"https://doi.org/10.1115/imece2000-1601","url":null,"abstract":"\u0000 Acoustic streaming theory, applied to micro-scale pumps is presented. A mathematical model based on streaming equations and Mason’s model [9] of the piezoelectric transducer is described. Using this model, the effect of geometric scaling, frequency variation, and excitation amplitude on head and flow rate are examined. The significance of high body forces in the AC boundary layer are demonstrated, along with their effect on mass flow rates for small geometries. It is shown that flow velocities are inversely proportional to the flow tube diameter for small sizes. Experimental data for a macro-scale pump is provided and used to corroborate the static head versus excitation relationship predicted by the model. Compression wave acoustic streaming pumps are shown to have potential viability for micro-scale applications.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125598775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The effect of foam core density and facesheet thickness on the low velocity impact response and damage evolution in homogeneous foam core sandwich composites was studied. The failure characteristics, initiation and evolution of damage as well as the effect of impact energy were investigated. A Dynatup 8210 Impact Test Machine was utilized to conduct the low-velocity impact tests. Characterization of the impact response was performed by comparing the impact load histories, impact plots and failure characteristics. Fractography analysis was conducted through the use of scanning electron microscopy (SEM) and optical microscopy. Three types of foam cores with different densities, namely Airlite B12.5, Rohacell IG-71R63 and Airex R63.5 foam cores, were used to study the effect of core density. Considering four groups of facesheets made of different layers of cross-ply carbon prepregs performed the effect of facesheet thickness. For all the facesheet thicknesses (0.011-0.894-cm thick) and impact energy (11-40 J) range considered in this study, the maximum load (Pm), deflection-at-maximum load (δm) and time-to-maximum load (tm) exhibited strong influence or dependence on the type of foam core as opposed to the facesheet thickness. The energy-to-maximum load (Em), total energy absorbed (Et) and total energy-to-impact energy (Et/Eimp) ratio became less sensitive on the foam core density (or type) with increasing facesheet thickness. A transition point from foam core to facesheet controlled impact behavior as a function of impact energy level was observed. The impact parameters varied either linearly or parabolically with impact energy depending on the impact energy level, type of foam core and facesheet thickness. Excellent repeatability of impact data was generally obtained with increase in foam core density.
{"title":"Effect of Foam Core Density and Facesheet Thickness on the Low Velocity Impact Response of Foam Core Sandwich Composites","authors":"M. Motuku, R. M. Rodgers, S. Jeelani, U. Vaidya","doi":"10.1115/imece2000-1633","DOIUrl":"https://doi.org/10.1115/imece2000-1633","url":null,"abstract":"\u0000 The effect of foam core density and facesheet thickness on the low velocity impact response and damage evolution in homogeneous foam core sandwich composites was studied. The failure characteristics, initiation and evolution of damage as well as the effect of impact energy were investigated. A Dynatup 8210 Impact Test Machine was utilized to conduct the low-velocity impact tests. Characterization of the impact response was performed by comparing the impact load histories, impact plots and failure characteristics. Fractography analysis was conducted through the use of scanning electron microscopy (SEM) and optical microscopy. Three types of foam cores with different densities, namely Airlite B12.5, Rohacell IG-71R63 and Airex R63.5 foam cores, were used to study the effect of core density. Considering four groups of facesheets made of different layers of cross-ply carbon prepregs performed the effect of facesheet thickness.\u0000 For all the facesheet thicknesses (0.011-0.894-cm thick) and impact energy (11-40 J) range considered in this study, the maximum load (Pm), deflection-at-maximum load (δm) and time-to-maximum load (tm) exhibited strong influence or dependence on the type of foam core as opposed to the facesheet thickness. The energy-to-maximum load (Em), total energy absorbed (Et) and total energy-to-impact energy (Et/Eimp) ratio became less sensitive on the foam core density (or type) with increasing facesheet thickness. A transition point from foam core to facesheet controlled impact behavior as a function of impact energy level was observed. The impact parameters varied either linearly or parabolically with impact energy depending on the impact energy level, type of foam core and facesheet thickness. Excellent repeatability of impact data was generally obtained with increase in foam core density.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134336891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Diffusive optical tomography [DOT] is a technique for imaging within the body. While DOT provides excellent results under good conditions, there are many situations (due to anatomy or other physical limitation) in which it suffers from a “limited view” problem. In this paper we discuss our work on a new technique for combining DOT with focused ultrasound to generate virtual sources of illumination. These virtual sources help overcome the limited view problem. We present our experimental results using laboratory tissue phantoms.
{"title":"Ultrasound Modulation of Diffusive Optical Waves for Medical Imaging","authors":"D. Townsend, J. Stott, Ronald A. Roy, C. DiMarzio","doi":"10.1115/imece2000-1605","DOIUrl":"https://doi.org/10.1115/imece2000-1605","url":null,"abstract":"\u0000 Diffusive optical tomography [DOT] is a technique for imaging within the body. While DOT provides excellent results under good conditions, there are many situations (due to anatomy or other physical limitation) in which it suffers from a “limited view” problem. In this paper we discuss our work on a new technique for combining DOT with focused ultrasound to generate virtual sources of illumination. These virtual sources help overcome the limited view problem. We present our experimental results using laboratory tissue phantoms.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130364833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents preliminary results from an analysis of the damping properties of a composite isogrid panel with an embedded viscoelastic layer by means of a finite element method (FEM) implementation of the modal strain energy method (MSE). Modal analysis shows that significant shear deformation occurs in the region between the ribs and the face skin because of the stiffness mismatch between the two. Since the performance of a viscoelastic polymer damping material is optimized by subjecting the material to shear deformation, such damping materials can be placed at the interface between the ribs and the skin in order to significantly improve the damping properties of composite isogrid structures. It is shown that the shear strain energy density (energy per volume) near the edges of the panel in the damping layer is much higher than that at the center area for the first free-free vibration mode. As a first attempt at improvement of damping, the effect of using different amounts of damping materials on the loss factor of the isogrid panel is also studied.
{"title":"Composite Isogrid Structures With Integral Passive Damping","authors":"Y. Chen, R. Gibson","doi":"10.1115/imece2000-1632","DOIUrl":"https://doi.org/10.1115/imece2000-1632","url":null,"abstract":"\u0000 This paper presents preliminary results from an analysis of the damping properties of a composite isogrid panel with an embedded viscoelastic layer by means of a finite element method (FEM) implementation of the modal strain energy method (MSE). Modal analysis shows that significant shear deformation occurs in the region between the ribs and the face skin because of the stiffness mismatch between the two. Since the performance of a viscoelastic polymer damping material is optimized by subjecting the material to shear deformation, such damping materials can be placed at the interface between the ribs and the skin in order to significantly improve the damping properties of composite isogrid structures. It is shown that the shear strain energy density (energy per volume) near the edges of the panel in the damping layer is much higher than that at the center area for the first free-free vibration mode. As a first attempt at improvement of damping, the effect of using different amounts of damping materials on the loss factor of the isogrid panel is also studied.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130074651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Abbot, C. Gedney, D. Morton, S. Celuzza, I. Dyer, Peter Ehlers, R. Vaicaitis, James Brown, A. Guinzburg, W. Hodgson
An extensive series of vibration and acoustic measurements has been conducted on a large (63 inch diameter three-vane impeller) centrifugal wastewater pump at a municipal pump station. Vibration measurements on the pump bearing housing exceeded the design specification at most operating blade-passing frequencies (BPF). The purpose of the testing was to determine the primary mechanisms of the vibration, including contributions from an acoustic resonance (within the piping system) and the pump’s hydrodynamic near-field. In Part 1, the physical mechanisms of pump vibration and overall experimental results are presented.
{"title":"Vibration and Acoustic Evaluation of a Large Centrifugal Wastewater Pump, Part 1: Background and Experiment","authors":"P. Abbot, C. Gedney, D. Morton, S. Celuzza, I. Dyer, Peter Ehlers, R. Vaicaitis, James Brown, A. Guinzburg, W. Hodgson","doi":"10.1115/imece2000-1610","DOIUrl":"https://doi.org/10.1115/imece2000-1610","url":null,"abstract":"\u0000 An extensive series of vibration and acoustic measurements has been conducted on a large (63 inch diameter three-vane impeller) centrifugal wastewater pump at a municipal pump station. Vibration measurements on the pump bearing housing exceeded the design specification at most operating blade-passing frequencies (BPF). The purpose of the testing was to determine the primary mechanisms of the vibration, including contributions from an acoustic resonance (within the piping system) and the pump’s hydrodynamic near-field. In Part 1, the physical mechanisms of pump vibration and overall experimental results are presented.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129196162","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A Newton-like method is designed for determining the shape or sought-after shape modifications of a scatterer from the knowledge of acoustic far-field patterns at a given number of observation points. This method distinguishes itself from existing numerical procedures by the following features: (a) exact Jacobian matrices for the linearized problems rather than approximate ones, (b) a fast numerical procedure for computing these Jacobian matrices, (c) a computationally efficient absorbing boundary condition for the finite element discretization, and (d) a numerically scalable domain decomposition methods for the fast solution of high-frequency direct acoustic scattering problems.
{"title":"Newton-Like Method for Solving Inverse Obstacle Acoustic Scattering Problems","authors":"R. Djellouli, C. Farhat, R. Tezaur","doi":"10.1115/imece2000-1594","DOIUrl":"https://doi.org/10.1115/imece2000-1594","url":null,"abstract":"\u0000 A Newton-like method is designed for determining the shape or sought-after shape modifications of a scatterer from the knowledge of acoustic far-field patterns at a given number of observation points. This method distinguishes itself from existing numerical procedures by the following features: (a) exact Jacobian matrices for the linearized problems rather than approximate ones, (b) a fast numerical procedure for computing these Jacobian matrices, (c) a computationally efficient absorbing boundary condition for the finite element discretization, and (d) a numerically scalable domain decomposition methods for the fast solution of high-frequency direct acoustic scattering problems.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114062555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Several algorithms are presented to improve noise source location using a microphone array. The estimation of the source location is essentially a two step process: first, time delays of arrivals (TDOA’s) are calculated using the unwrapped phase (UP) method; then the TDOA estimates are used to determine the coordinates of the source. The first algorithm was developed to calculate TDOA’s automatically by removing the data points with low coherence from the unwrapped phase and by using a delay error rather than a mean square error to choose the best distance estimate. A simplex algorithm was then implemented to evaluate source coordinates from the TDOA’s. Finally, a pruning algorithm was devised to remove unreliable data from the source coordinate calculations. Experimental data is presented to illustrate the use and benefits of these algorithms.
{"title":"New Algorithms to Improve Noise Source Location Using a Microphone Array","authors":"C. Darvennes, Tarun Bhatt","doi":"10.1115/imece2000-1619","DOIUrl":"https://doi.org/10.1115/imece2000-1619","url":null,"abstract":"\u0000 Several algorithms are presented to improve noise source location using a microphone array. The estimation of the source location is essentially a two step process: first, time delays of arrivals (TDOA’s) are calculated using the unwrapped phase (UP) method; then the TDOA estimates are used to determine the coordinates of the source. The first algorithm was developed to calculate TDOA’s automatically by removing the data points with low coherence from the unwrapped phase and by using a delay error rather than a mean square error to choose the best distance estimate. A simplex algorithm was then implemented to evaluate source coordinates from the TDOA’s. Finally, a pruning algorithm was devised to remove unreliable data from the source coordinate calculations. Experimental data is presented to illustrate the use and benefits of these algorithms.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127510879","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A time domain method for identifying middle to high frequency system parameters from sound and vibration measurements is presented. This work is part of a beginning investigation with an objective of enhancing experimental Statistical Energy Analysis (SEA). Thus far, it is seen that a state space realization method can be used to identify a first order power flow model from measured transient power and energy data. Specifically, the Eigensystem Realization Algorithm (ERA) is observed to accurately identify a minimum order model for a simple system. Additionally, it is found that the identified model can be used to improve an existing SEA model of the system.
{"title":"Realization of a Minimum-Order Power Flow Model and SEA Model Updating Using Time Domain Measurements","authors":"J. Gregory, R. Keltie, F. D. Caulfield","doi":"10.1115/imece2000-1616","DOIUrl":"https://doi.org/10.1115/imece2000-1616","url":null,"abstract":"\u0000 A time domain method for identifying middle to high frequency system parameters from sound and vibration measurements is presented. This work is part of a beginning investigation with an objective of enhancing experimental Statistical Energy Analysis (SEA). Thus far, it is seen that a state space realization method can be used to identify a first order power flow model from measured transient power and energy data. Specifically, the Eigensystem Realization Algorithm (ERA) is observed to accurately identify a minimum order model for a simple system. Additionally, it is found that the identified model can be used to improve an existing SEA model of the system.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132608870","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A method for field measurement of timber pile length in bridge foundations is possible by determining the natural frequency spacing between consecutive resonant peaks in the longitudinal frequency response function (FRF) as well as experimental determination of the longitudinal wave speed. The measurement procedure relies on vibration modes excited through the attachment of small actuators driven with random input and the recorded response of attached accelerometers. The identification of natural frequencies in timber piles is complicated by the inhomogeneous nature of wood and the location of measurement points at possible longitudinal nodes along the pile. Missing peaks and corrupted spectrums are common in the experimental data collected during the testing of timber piles. A form of cepstral analysis using the FRF shows promise towards overcoming some of the inherent difficulties in identifying the natural frequency spacing between resonant peaks in the spectrum. The details of the signal processing and natural frequency spacing identification are presented and demonstrated on a laboratory aluminum bar and typical timber pile data.
{"title":"Cepstral Analysis Applied to Identification of Longitudinal Vibration in Timber Piles","authors":"S. Pardue, M. Renfro, Prasanna K. Ramsagar","doi":"10.1115/imece2000-1618","DOIUrl":"https://doi.org/10.1115/imece2000-1618","url":null,"abstract":"\u0000 A method for field measurement of timber pile length in bridge foundations is possible by determining the natural frequency spacing between consecutive resonant peaks in the longitudinal frequency response function (FRF) as well as experimental determination of the longitudinal wave speed. The measurement procedure relies on vibration modes excited through the attachment of small actuators driven with random input and the recorded response of attached accelerometers.\u0000 The identification of natural frequencies in timber piles is complicated by the inhomogeneous nature of wood and the location of measurement points at possible longitudinal nodes along the pile. Missing peaks and corrupted spectrums are common in the experimental data collected during the testing of timber piles. A form of cepstral analysis using the FRF shows promise towards overcoming some of the inherent difficulties in identifying the natural frequency spacing between resonant peaks in the spectrum.\u0000 The details of the signal processing and natural frequency spacing identification are presented and demonstrated on a laboratory aluminum bar and typical timber pile data.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129347341","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
James E. Howell, N. Humbad, J. Hargrove, Robert A. Porada
Noise from automotive air handling systems is an important issue for driver comfort. This study was undertaken to quantify the noise from the air handling system and to develop a predictive model for the noise level and spectrum at the drivers right ear location. Tests were conducted on six vehicles to develop the predictive model and then four more vehicles were tested and used to verify the prediction model. All vehicles tested were production level designs ranging from small economy cars to large luxury trucks. The study shows that the noise generated by the air handling system can be modeled with the parameters of static pressure across the blower (ΔP) and system air flow rate (Q). When the measured noise levels were compared to the predicted noise levels, there was a mean error of −0.03 dBA with a standard deviation of 1.31 dBA for all vehicles and for various modes of operation. This model can be used in the early stages of design using CFD/CAE analysis, or in evaluating the effects of design changes on the sound pressure level and spectrum.
{"title":"Flow Noise Predictions for Automotive Air Rush Noise","authors":"James E. Howell, N. Humbad, J. Hargrove, Robert A. Porada","doi":"10.1115/imece2000-1615","DOIUrl":"https://doi.org/10.1115/imece2000-1615","url":null,"abstract":"\u0000 Noise from automotive air handling systems is an important issue for driver comfort. This study was undertaken to quantify the noise from the air handling system and to develop a predictive model for the noise level and spectrum at the drivers right ear location. Tests were conducted on six vehicles to develop the predictive model and then four more vehicles were tested and used to verify the prediction model. All vehicles tested were production level designs ranging from small economy cars to large luxury trucks. The study shows that the noise generated by the air handling system can be modeled with the parameters of static pressure across the blower (ΔP) and system air flow rate (Q). When the measured noise levels were compared to the predicted noise levels, there was a mean error of −0.03 dBA with a standard deviation of 1.31 dBA for all vehicles and for various modes of operation. This model can be used in the early stages of design using CFD/CAE analysis, or in evaluating the effects of design changes on the sound pressure level and spectrum.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116645818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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