Pub Date : 2001-11-11DOI: 10.1115/imece2001/nca-23526
G. Koopmann, D. Ericson, Adam Olchowski, E. Salesky
In this paper we describe a method for optimally tuning a bell to ‘best fit’ a specified sound spectrum. The method links the disciplines of structural dynamics, acoustics and optimization into a unified methodology. The design variables center on the addition of masses (size, number and location). The design variables are treated as external forces (via their impedances) in the equation that describes the bell dynamics as a series expansion of eigen functions. This step eliminates the need for solution of large matrix eigenvalue problems. An acoustic program POWER is used to assess the bell’s radiated sound power as a function of the design variables. Various search engines are used within the computer program MATLAB® to determine which design variables give the ‘best fit’ to the acoustic specifications.
{"title":"Tuning a Replica of the Liberty Bell via Material Tailoring: An Application of a Method for Optimal Acoustic Design","authors":"G. Koopmann, D. Ericson, Adam Olchowski, E. Salesky","doi":"10.1115/imece2001/nca-23526","DOIUrl":"https://doi.org/10.1115/imece2001/nca-23526","url":null,"abstract":"\u0000 In this paper we describe a method for optimally tuning a bell to ‘best fit’ a specified sound spectrum. The method links the disciplines of structural dynamics, acoustics and optimization into a unified methodology. The design variables center on the addition of masses (size, number and location). The design variables are treated as external forces (via their impedances) in the equation that describes the bell dynamics as a series expansion of eigen functions. This step eliminates the need for solution of large matrix eigenvalue problems. An acoustic program POWER is used to assess the bell’s radiated sound power as a function of the design variables. Various search engines are used within the computer program MATLAB® to determine which design variables give the ‘best fit’ to the acoustic specifications.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116443544","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}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/nca-23523
R. Nagem, G. Sandri
We investigate the effects of fluid viscosity on the diffraction of a time-harmonic acoustic plane wave by a semi-infinite half-plane. A boundary layer approximation based on a multiple scale expansion and the known inviscid diffraction solution is used to derive the velocity field near the surface of the half-plane. The boundary layer approximation is compared to an independent incompressible viscous flow solution that is derived for a small circular region in the neighborhood of the edge of the half-plane.
{"title":"Boundary Layer Analysis of Acoustic Diffraction by a Half-Plane in a Viscous Fluid Medium","authors":"R. Nagem, G. Sandri","doi":"10.1115/imece2001/nca-23523","DOIUrl":"https://doi.org/10.1115/imece2001/nca-23523","url":null,"abstract":"\u0000 We investigate the effects of fluid viscosity on the diffraction of a time-harmonic acoustic plane wave by a semi-infinite half-plane. A boundary layer approximation based on a multiple scale expansion and the known inviscid diffraction solution is used to derive the velocity field near the surface of the half-plane. The boundary layer approximation is compared to an independent incompressible viscous flow solution that is derived for a small circular region in the neighborhood of the edge of the half-plane.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121633609","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}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/nca-23517
M. Poese, S. Garrett
Glassblowers observed the generation of sound in the presence of temperature gradients over one hundred years ago. It was less than twenty years ago that the reverse process — the use of high-amplitude sound to produce refrigeration — was first demonstrated. Due to the discovery of the “hole-in-the-ozone” and the ratification of the Montreal Protocols, research in thermoacoustics has accelerated during the past decade. In 1992, an electrically powered thermoacoustic refrigerator was placed in orbit on the Space Shuttle and a larger thermoacoustic chiller for shipboard electronics was operated to cool radar equipment for a week on board a US Navy destroyer in 1995. More recently, a heat-driven thermoacoustic device, built by the team at Los Alamos, was used to liquefy natural gas at a rate in excess of 140 gal/day by burning part of the gas stream.
{"title":"Introduction to Thermoacoustic Engines and Refrigerators","authors":"M. Poese, S. Garrett","doi":"10.1115/imece2001/nca-23517","DOIUrl":"https://doi.org/10.1115/imece2001/nca-23517","url":null,"abstract":"\u0000 Glassblowers observed the generation of sound in the presence of temperature gradients over one hundred years ago. It was less than twenty years ago that the reverse process — the use of high-amplitude sound to produce refrigeration — was first demonstrated. Due to the discovery of the “hole-in-the-ozone” and the ratification of the Montreal Protocols, research in thermoacoustics has accelerated during the past decade. In 1992, an electrically powered thermoacoustic refrigerator was placed in orbit on the Space Shuttle and a larger thermoacoustic chiller for shipboard electronics was operated to cool radar equipment for a week on board a US Navy destroyer in 1995. More recently, a heat-driven thermoacoustic device, built by the team at Los Alamos, was used to liquefy natural gas at a rate in excess of 140 gal/day by burning part of the gas stream.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126286575","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}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/nca-23531
N. Sidorovskaia
A new numerical algorithm for obtaining a normal mode solution of the Helmholtz equation for an arbitrary sound speed profile in the ocean is discussed. The new method represents the solution as a series expansion in terms of basis modal functions corresponding to the solution of a reference iso-velocity problem. The numerical optimization procedures that allow improving the computational performance of the code are considered. An important advantage of the presented algorithm is a straightforward transformation of the solution into spherical representation suitable for mapping an incident waveguide field into a scattered one to describe a scattering process from an elastic object in a waveguide. The mathematical formulation of the transformation is presented. The numerical model has already proved to be competitive with Navy standard propagation simulation tools.
{"title":"A New Numerical Technique for the Unification of Propagation and Scattering Problems in Underwater Acoustics","authors":"N. Sidorovskaia","doi":"10.1115/imece2001/nca-23531","DOIUrl":"https://doi.org/10.1115/imece2001/nca-23531","url":null,"abstract":"\u0000 A new numerical algorithm for obtaining a normal mode solution of the Helmholtz equation for an arbitrary sound speed profile in the ocean is discussed. The new method represents the solution as a series expansion in terms of basis modal functions corresponding to the solution of a reference iso-velocity problem. The numerical optimization procedures that allow improving the computational performance of the code are considered. An important advantage of the presented algorithm is a straightforward transformation of the solution into spherical representation suitable for mapping an incident waveguide field into a scattered one to describe a scattering process from an elastic object in a waveguide. The mathematical formulation of the transformation is presented. The numerical model has already proved to be competitive with Navy standard propagation simulation tools.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121973740","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}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/nca-23503
B. Greska, A. Krothapalli
This paper describes a newly built experimental facility at the Florida State University to develop innovative technologies for the noise suppression and mixing control of high-speed jets. This facility is capable of generating jet flows up to a maximum jet exit Mach number of about 2.5 at stagnation temperatures reaching up to 1500K. The facility can accommodate nozzles having an exit diameter of about 80 mm. At the maximum operating conditions, the jet can be run continuously for about 15 minutes. The jet exhausts into an anechoic room that measures 5.2 m (width) × 5.8 m (length) × 4 m (height). A sudden expansion (SUE) burner using Ethylene as its fuel is used to heat the high-pressure air. The instrumentation includes: High Resolution Infrared camera, stereoscopic Particle Image Velocimetry and Laser Speckle Displacement method for flow field measurements, high temperature unsteady pressure probes for the measurement of pressure fluctuations in the hydrodynamic field, and microphones with high speed data acquisition for far-field narrow band sound measurements.
{"title":"High Temperature Supersonic Jet Facility for Aeroacoustic Studies","authors":"B. Greska, A. Krothapalli","doi":"10.1115/imece2001/nca-23503","DOIUrl":"https://doi.org/10.1115/imece2001/nca-23503","url":null,"abstract":"\u0000 This paper describes a newly built experimental facility at the Florida State University to develop innovative technologies for the noise suppression and mixing control of high-speed jets. This facility is capable of generating jet flows up to a maximum jet exit Mach number of about 2.5 at stagnation temperatures reaching up to 1500K. The facility can accommodate nozzles having an exit diameter of about 80 mm. At the maximum operating conditions, the jet can be run continuously for about 15 minutes. The jet exhausts into an anechoic room that measures 5.2 m (width) × 5.8 m (length) × 4 m (height). A sudden expansion (SUE) burner using Ethylene as its fuel is used to heat the high-pressure air. The instrumentation includes: High Resolution Infrared camera, stereoscopic Particle Image Velocimetry and Laser Speckle Displacement method for flow field measurements, high temperature unsteady pressure probes for the measurement of pressure fluctuations in the hydrodynamic field, and microphones with high speed data acquisition for far-field narrow band sound measurements.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130538682","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}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/nca-23515
P. Shorter, B. Gardner, A. Patil
The response of a structural-acoustic system in the mid-frequency range typically consists of both long and short wavelength behavior. Modeling the short-wavelength behavior deterministically is usually computationally prohibitive and structural-acoustic techniques such as SEA are often adopted. However, SEA cannot adequately capture the long-wavelength global behavior of the system. Recent work aimed at addressing the mid-frequency problem has led to the development of a hybrid approach based on a wavenumber partitioning scheme [1]. This paper provides an overview of the approach and presents some recent research developments.
{"title":"Resound: A Full Spectrum Modelling Method","authors":"P. Shorter, B. Gardner, A. Patil","doi":"10.1115/imece2001/nca-23515","DOIUrl":"https://doi.org/10.1115/imece2001/nca-23515","url":null,"abstract":"\u0000 The response of a structural-acoustic system in the mid-frequency range typically consists of both long and short wavelength behavior. Modeling the short-wavelength behavior deterministically is usually computationally prohibitive and structural-acoustic techniques such as SEA are often adopted. However, SEA cannot adequately capture the long-wavelength global behavior of the system. Recent work aimed at addressing the mid-frequency problem has led to the development of a hybrid approach based on a wavenumber partitioning scheme [1]. This paper provides an overview of the approach and presents some recent research developments.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133015261","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}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/nca-23533
O. Baysal, M. Idres
A novel mathematical model and its solution are presented to simulate the generation and the propagation of supersonic jet noise. An objective in developing this model was to seek an approach that would be feasible in a design environment, where a number of consecutive simulations would be needed. Hence, a judicious compromise was afforded between the computational efficiency and the overall accuracy of the methodology in representing the underlying physics. The noise generation was modeled as axisymmetric or helical instabilities introduced in the upstream boundary. The propagation was simulated by solving the three-dimensional and linearized Euler equations in a very efficient way by a dispersion-relation-preserving scheme. The predicted relative values of the sound pressure level contours have successfully been compared with the experimental data and other computational approaches.
{"title":"Computation of Noise From Fully-Expanded Supersonic Jet Using Low-Dispersion Methodology","authors":"O. Baysal, M. Idres","doi":"10.1115/imece2001/nca-23533","DOIUrl":"https://doi.org/10.1115/imece2001/nca-23533","url":null,"abstract":"\u0000 A novel mathematical model and its solution are presented to simulate the generation and the propagation of supersonic jet noise. An objective in developing this model was to seek an approach that would be feasible in a design environment, where a number of consecutive simulations would be needed. Hence, a judicious compromise was afforded between the computational efficiency and the overall accuracy of the methodology in representing the underlying physics. The noise generation was modeled as axisymmetric or helical instabilities introduced in the upstream boundary. The propagation was simulated by solving the three-dimensional and linearized Euler equations in a very efficient way by a dispersion-relation-preserving scheme. The predicted relative values of the sound pressure level contours have successfully been compared with the experimental data and other computational approaches.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133040990","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}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/nca-23530
G. Feijoo, A. Oberai, P. Pinsky
We present a method to calculate the derivative of a functional that depends on the shape of a body immersed in an acoustic media. The functional depends implicitly on the shape through the solution of an exterior acoustic problem. The derivative is calculated in terms of the solution of the primal problem and an auxiliary problem, the adjoint problem. An important aspect of this method is that the cost of calculating the derivative is independent of the number of parameters used to represent the shape of the body. This allows for efficient solution of optimization problems in structural acoustics.
{"title":"Shape Sensitivity Analysis Applied to Exterior Acoustics","authors":"G. Feijoo, A. Oberai, P. Pinsky","doi":"10.1115/imece2001/nca-23530","DOIUrl":"https://doi.org/10.1115/imece2001/nca-23530","url":null,"abstract":"\u0000 We present a method to calculate the derivative of a functional that depends on the shape of a body immersed in an acoustic media. The functional depends implicitly on the shape through the solution of an exterior acoustic problem. The derivative is calculated in terms of the solution of the primal problem and an auxiliary problem, the adjoint problem. An important aspect of this method is that the cost of calculating the derivative is independent of the number of parameters used to represent the shape of the body. This allows for efficient solution of optimization problems in structural acoustics.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133493662","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}
Acoustic time reversal is a process in which acoustic energy received at an array is recorded, time-reversed, and then rebroadcast through the same or a collocated array. The result is that the original signal is “retrofocused” in time and space to the original source location without regard to the propagation paths or characteristics of the complex media between source and receiver. The array used for receive and rebroadcast, together with the data acquisition and processing system, is referred to as a time reversal mirror (TRM). Adaptation of time reversal mirrors to the problem of water tunnel acoustic measurements is examined. A concept demonstration test is planned for the Garfield Thomas Water Tunnel (GTWT) at the Pennsylvania State University Applied Research Laboratory, with the objective of demonstrating improved acoustic measurement capabilities compared to other conventional measurement techniques. An outline of the planned test is presented, as well as results from preliminary water tank testing of the arrays and instrumentation to be used in the GTWT experiment. A mathematical description of the time reversal mirror is developed, and preliminary conclusions regarding expected TRM performance in the water tunnel environment and limitations of the proposed measurement scheme are discussed.
{"title":"Water Tunnel Acoustic Measurements Using a Time Reversal Mirror","authors":"C. Barber, G. Lauchle, D. Capone","doi":"10.1121/1.4777349","DOIUrl":"https://doi.org/10.1121/1.4777349","url":null,"abstract":"\u0000 Acoustic time reversal is a process in which acoustic energy received at an array is recorded, time-reversed, and then rebroadcast through the same or a collocated array. The result is that the original signal is “retrofocused” in time and space to the original source location without regard to the propagation paths or characteristics of the complex media between source and receiver. The array used for receive and rebroadcast, together with the data acquisition and processing system, is referred to as a time reversal mirror (TRM). Adaptation of time reversal mirrors to the problem of water tunnel acoustic measurements is examined. A concept demonstration test is planned for the Garfield Thomas Water Tunnel (GTWT) at the Pennsylvania State University Applied Research Laboratory, with the objective of demonstrating improved acoustic measurement capabilities compared to other conventional measurement techniques. An outline of the planned test is presented, as well as results from preliminary water tank testing of the arrays and instrumentation to be used in the GTWT experiment. A mathematical description of the time reversal mirror is developed, and preliminary conclusions regarding expected TRM performance in the water tunnel environment and limitations of the proposed measurement scheme are discussed.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113963205","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 investigates the experimental vibration technique of impact excitation when used to determine modal damping. Current practices introduce a consistent bias error in the derived modal damping estimates. The error can be significant, with levels of damping being wrongly predicted by a factor of three or more. This paper identifies the source of the error, and derives a simple correction to be applied to the observed modal damping estimates. The procedure is demonstrated by experiment and the results of a round robin exercise.
{"title":"Correcting a Significant Bias Error in the Modal Damping Determined Using Transient Vibration Data","authors":"C. Ratcliffe","doi":"10.1115/imece2000-1625","DOIUrl":"https://doi.org/10.1115/imece2000-1625","url":null,"abstract":"\u0000 This paper investigates the experimental vibration technique of impact excitation when used to determine modal damping. Current practices introduce a consistent bias error in the derived modal damping estimates. The error can be significant, with levels of damping being wrongly predicted by a factor of three or more. This paper identifies the source of the error, and derives a simple correction to be applied to the observed modal damping estimates. The procedure is demonstrated by experiment and the results of a round robin exercise.","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":"122489235","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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