N. Humbad, Richard Prevost, J. Foss, Charles C. Chen
The climate control air handling system is one of the major contributors to automobile interior noise. The most annoying features can be characterized as low frequency (<= 400 Hz) “rumble”, and “blade passing frequency, BPF tone” noise. This study presents an experimental investigation for two blower scroll assemblies, namely ‘baseline’ and ‘modified’. The baseline assembly is the original scroll which exhibited both tone and rumble noise problems. This assembly was modified to significantly reduce the tone and rumble noise. The velocity power spectral density plots of flow velocity show areas within the blower scroll where the turbulence fluctuations are relatively high for the tone and rumble frequencies, and are lower in magnitude for the modified case. A detailed CFD analysis was performed to compare the mean flow velocity components for the two assemblies. The results are in good agreement with the measurements. CFD analyses, which have been confirmed by experimental data, can be used to predict beneficial geometric alterations to minimize the tonal and rumble noise sources in climate control flow systems.
{"title":"Flow Measurements and Analysis for Automotive Blower Noise","authors":"N. Humbad, Richard Prevost, J. Foss, Charles C. Chen","doi":"10.1115/imece1999-0190","DOIUrl":"https://doi.org/10.1115/imece1999-0190","url":null,"abstract":"\u0000 The climate control air handling system is one of the major contributors to automobile interior noise. The most annoying features can be characterized as low frequency (<= 400 Hz) “rumble”, and “blade passing frequency, BPF tone” noise. This study presents an experimental investigation for two blower scroll assemblies, namely ‘baseline’ and ‘modified’. The baseline assembly is the original scroll which exhibited both tone and rumble noise problems. This assembly was modified to significantly reduce the tone and rumble noise. The velocity power spectral density plots of flow velocity show areas within the blower scroll where the turbulence fluctuations are relatively high for the tone and rumble frequencies, and are lower in magnitude for the modified case. A detailed CFD analysis was performed to compare the mean flow velocity components for the two assemblies. The results are in good agreement with the measurements. CFD analyses, which have been confirmed by experimental data, can be used to predict beneficial geometric alterations to minimize the tonal and rumble noise sources in climate control flow systems.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114381683","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}
Asymptotic and exact local radiation boundary conditions first derived by Hagstrom and Hariharan are reformulated as an auxiliary Cauchy problem for linear first-order systems of ordinary equations on the boundary for each harmonic on a circle or sphere in two- or three-dimensions, respectively. With this reformulation, the resulting radiation boundary condition involves first-order derivatives only and can be computed efficiently and concurrently with standard semi-discrete finite element methods for the near-field solution without changing the banded/sparse structure of the finite element equations. In 3D, with the number of equations in the Cauchy problem equal to the mode number, this reformulation is exact. If fewer equations are used, then the boundary conditions form uniform asymptotic approximations to the exact condition. Furthermore, using this approach, we formulate accurate radiation boundary conditions for the two-dimensional unbounded problem on a circle. Numerical studies of time-dependent radiation and scattering are performed to assess the accuracy and convergence properties of the boundary conditions when implemented in the finite element method. The results demonstrate that the new formulation has dramatically improved accuracy and efficiency for time domain simulations compared to standard boundary treatments.
{"title":"Asymptotic and Exact Radiation Boundary Conditions for Time-Dependent Scattering","authors":"L. Thompson, R. Huan","doi":"10.1115/imece1999-0236","DOIUrl":"https://doi.org/10.1115/imece1999-0236","url":null,"abstract":"\u0000 Asymptotic and exact local radiation boundary conditions first derived by Hagstrom and Hariharan are reformulated as an auxiliary Cauchy problem for linear first-order systems of ordinary equations on the boundary for each harmonic on a circle or sphere in two- or three-dimensions, respectively. With this reformulation, the resulting radiation boundary condition involves first-order derivatives only and can be computed efficiently and concurrently with standard semi-discrete finite element methods for the near-field solution without changing the banded/sparse structure of the finite element equations. In 3D, with the number of equations in the Cauchy problem equal to the mode number, this reformulation is exact. If fewer equations are used, then the boundary conditions form uniform asymptotic approximations to the exact condition. Furthermore, using this approach, we formulate accurate radiation boundary conditions for the two-dimensional unbounded problem on a circle. Numerical studies of time-dependent radiation and scattering are performed to assess the accuracy and convergence properties of the boundary conditions when implemented in the finite element method. The results demonstrate that the new formulation has dramatically improved accuracy and efficiency for time domain simulations compared to standard boundary treatments.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126874671","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}
Air-flotation ovens are used for non-contact drying of coated web materials such as photographic film, magnetic media, and paper. In a typical air-flotation oven, the air bars are arranged in such a way that the path of web is nearly sinusoidal. When web tension fluctuates, the distance between the web and the air bars also changes. This phenomenon affects the longitudinal dynamics and tension control of an air-floated web. In some cases, tension fluctuations can cause the web to touch the air bars, resulting in damage to the coating and the web. This paper discusses an analytical model of the extensional resiliency of an air-floated web. The analysis shows that at low tension the longitudinal stiffness of an air-floated web is small, being dominated by the air cushion effects. At higher web tension, however, the effects of material deformation become more important than the air cushion effects. The analysis is compared with the experimental results obtained in a pilot air-flotation oven. The analytical and experimental results show the same trends, though the analytical model tends to underpredict the longitudinal stiffness of air-supported webs.
{"title":"Longitudinal and Out-of-Plane Stiffness of a Web in an Air-Flotation Oven","authors":"Y. Chang, R. P. Swanson, Peter M. Moretti","doi":"10.1115/imece1999-0226","DOIUrl":"https://doi.org/10.1115/imece1999-0226","url":null,"abstract":"\u0000 Air-flotation ovens are used for non-contact drying of coated web materials such as photographic film, magnetic media, and paper. In a typical air-flotation oven, the air bars are arranged in such a way that the path of web is nearly sinusoidal. When web tension fluctuates, the distance between the web and the air bars also changes. This phenomenon affects the longitudinal dynamics and tension control of an air-floated web. In some cases, tension fluctuations can cause the web to touch the air bars, resulting in damage to the coating and the web. This paper discusses an analytical model of the extensional resiliency of an air-floated web. The analysis shows that at low tension the longitudinal stiffness of an air-floated web is small, being dominated by the air cushion effects. At higher web tension, however, the effects of material deformation become more important than the air cushion effects. The analysis is compared with the experimental results obtained in a pilot air-flotation oven. The analytical and experimental results show the same trends, though the analytical model tends to underpredict the longitudinal stiffness of air-supported webs.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128134372","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}
Exact Dirichlet-to-Neumann (DtN) radiation boundary conditions are derived in elliptic and spheroidal coordinates and formulated in a finite element method for the Helmholtz equation in unbounded domains. The DtN map matches the first N wave harmonics exactly at the artificial boundary. The use of elliptic and spheroidal boundaries enables the efficient solution of scattering from elongated objects in two- and three-dimensions respectively. Modified DtN conditions based on first and second order local boundary operators are also derived in elliptic and spheroidal coordinates, in a form suitable for finite element implementation. The modified DtN conditions are more accurate than the DtN boundary condition, yet require no extra memory and little extra cost. Direct implementation involves non-local spatial integrals leading to a dense, fully populated submatrix. A matrix-free interpretation of the non-local DtN map for elliptic and spheroidal boundaries, suitable for iterative solution of the resulting complex-symmetric system is described. For both the DtN and modified DtN conditions, we describe efficient and effective SSOR preconditioners with Eisenstat’s trick based on the matrix partition associated with the interior mesh and local boundary operator. Numerical examples of scattering from elliptic and spheroidal boundaries are computed to demonstrate the efficiency and accuracy of the boundary treatments for elongated structures.
{"title":"Finite Element Formulation of Exact Dirichlet-to-Neumann Radiation Conditions on Elliptic and Spheroidal Boundaries","authors":"L. Thompson, R. Huan, Cristian Ianculescu","doi":"10.1115/imece1999-0235","DOIUrl":"https://doi.org/10.1115/imece1999-0235","url":null,"abstract":"\u0000 Exact Dirichlet-to-Neumann (DtN) radiation boundary conditions are derived in elliptic and spheroidal coordinates and formulated in a finite element method for the Helmholtz equation in unbounded domains. The DtN map matches the first N wave harmonics exactly at the artificial boundary. The use of elliptic and spheroidal boundaries enables the efficient solution of scattering from elongated objects in two- and three-dimensions respectively. Modified DtN conditions based on first and second order local boundary operators are also derived in elliptic and spheroidal coordinates, in a form suitable for finite element implementation. The modified DtN conditions are more accurate than the DtN boundary condition, yet require no extra memory and little extra cost. Direct implementation involves non-local spatial integrals leading to a dense, fully populated submatrix. A matrix-free interpretation of the non-local DtN map for elliptic and spheroidal boundaries, suitable for iterative solution of the resulting complex-symmetric system is described. For both the DtN and modified DtN conditions, we describe efficient and effective SSOR preconditioners with Eisenstat’s trick based on the matrix partition associated with the interior mesh and local boundary operator. Numerical examples of scattering from elliptic and spheroidal boundaries are computed to demonstrate the efficiency and accuracy of the boundary treatments for elongated structures.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134391286","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 an elasticity theory solution for computation of acoustic radiation by a point- or line-excited fluid-loaded laminated plate, which may consist of a stack of an arbitrary number of different isotropic material layers. A one-side water-loaded three-layer sandwich plate, which consists of a hard rubber core sandwiched between two steel plates of equal thickness, was used as an example of the laminated plates. The approximated equivalent sandwich plate solutions were compared with the elasticity theory solutions. These results show that the approximated solutions are, as expected, valid only at frequencies much lower than the coincidence frequency. The numerical result also shows that, even at about one-tenth of the coincidence frequency, the approximated solutions suffer substantial error. The differences between the dry-side- and the wet-side-excited radiated fields of a single-layer uniform plate and a sandwich plate were investigated and compared, and found to be significantly different at frequencies above the coincidence frequency.
{"title":"Acoustic Radiation by Point- or Line-Excited Laminated Plates","authors":"Y. Hwang, M. Kim, P. Zoccola","doi":"10.1115/1.1303823","DOIUrl":"https://doi.org/10.1115/1.1303823","url":null,"abstract":"\u0000 This paper presents an elasticity theory solution for computation of acoustic radiation by a point- or line-excited fluid-loaded laminated plate, which may consist of a stack of an arbitrary number of different isotropic material layers. A one-side water-loaded three-layer sandwich plate, which consists of a hard rubber core sandwiched between two steel plates of equal thickness, was used as an example of the laminated plates. The approximated equivalent sandwich plate solutions were compared with the elasticity theory solutions. These results show that the approximated solutions are, as expected, valid only at frequencies much lower than the coincidence frequency. The numerical result also shows that, even at about one-tenth of the coincidence frequency, the approximated solutions suffer substantial error. The differences between the dry-side- and the wet-side-excited radiated fields of a single-layer uniform plate and a sandwich plate were investigated and compared, and found to be significantly different at frequencies above the coincidence frequency.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129675485","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}
Analytical formulae for both the velocity spectrum and the acoustic far-field radiated sound pressure for a doubly rib-stiffened (small frames and bulkheads) fluid-loaded elastic plate, excited by several different force distributions, are derived. The force distributions are (1) a line-force applied at a single point and (2) two Gaussian distributed force intensities whose effective width either spans the small rib spacing or the large rib spacing. The far-field sound pressure as a function of frequency is calculated. The concentrated line force case shows evidence of frame interference effects (sometimes referred to as Bloch waves) in the radiated pressure fields. These arise from coherent interaction of the pressure fields emanating from the frame reaction forces and the applied force pressure field. The frequencies at which these coherence effects are manifest depend on the stiffeners’ spacing as compared to the fluid-loaded flexural wavelength. The Gaussian force distribution eliminates these interaction effects depending on whether or not the effective force width is greater or less than the respective rib spacing.
{"title":"Force Distribution Dependence of Sound Radiation From a Doubly Rib-Stiffened Plate","authors":"D. Feit, Daniel T. Diperna","doi":"10.1115/imece1999-0234","DOIUrl":"https://doi.org/10.1115/imece1999-0234","url":null,"abstract":"\u0000 Analytical formulae for both the velocity spectrum and the acoustic far-field radiated sound pressure for a doubly rib-stiffened (small frames and bulkheads) fluid-loaded elastic plate, excited by several different force distributions, are derived. The force distributions are (1) a line-force applied at a single point and (2) two Gaussian distributed force intensities whose effective width either spans the small rib spacing or the large rib spacing. The far-field sound pressure as a function of frequency is calculated. The concentrated line force case shows evidence of frame interference effects (sometimes referred to as Bloch waves) in the radiated pressure fields. These arise from coherent interaction of the pressure fields emanating from the frame reaction forces and the applied force pressure field. The frequencies at which these coherence effects are manifest depend on the stiffeners’ spacing as compared to the fluid-loaded flexural wavelength. The Gaussian force distribution eliminates these interaction effects depending on whether or not the effective force width is greater or less than the respective rib spacing.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127616235","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 prediction of sound transmission through a thin elastic plate such as a window is an important problem in the field of noise control engineering. Integral equations which express sound fields in infinite half spaces which are divided off by the baffle and the elastic plate are introduced and combined with the equation of plate vibration to solve as a coupled system. The image method is used in every equation to reduce unknown functions and boundaries which should be considered. Some numerical examples are solved numerically to examine the method.
{"title":"The Sound Transmission Through a Baffled, Thin, Finite, Elastic Plate by Using Boundary Integral Equations","authors":"Y. Kawai","doi":"10.1115/imece1999-0229","DOIUrl":"https://doi.org/10.1115/imece1999-0229","url":null,"abstract":"\u0000 The prediction of sound transmission through a thin elastic plate such as a window is an important problem in the field of noise control engineering. Integral equations which express sound fields in infinite half spaces which are divided off by the baffle and the elastic plate are introduced and combined with the equation of plate vibration to solve as a coupled system. The image method is used in every equation to reduce unknown functions and boundaries which should be considered. Some numerical examples are solved numerically to examine the method.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116102577","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}
In ultrasonic nondestructive evaluation and sonar imaging, scattering contributions by leaky waves on truncated objects can be important for enhancing the visibility of certain of the borders of the scatterer. A method of approximating the leaky wave contributions is reviewed together with recent experimental and computational tests for evaluating that method in situations where the scattering contributions are large. The tests include meridional ray contributions to the scattering by tilted solid cylinders and cylindrical shells and Rayleigh wave contributions for steel cubes in water.
{"title":"Leaky Wave Contributions to Ultrasonic Scattering Amplitudes for Truncated Objects","authors":"P. Marston, S. Morse, K. Gipson","doi":"10.1115/imece1999-0221","DOIUrl":"https://doi.org/10.1115/imece1999-0221","url":null,"abstract":"\u0000 In ultrasonic nondestructive evaluation and sonar imaging, scattering contributions by leaky waves on truncated objects can be important for enhancing the visibility of certain of the borders of the scatterer. A method of approximating the leaky wave contributions is reviewed together with recent experimental and computational tests for evaluating that method in situations where the scattering contributions are large. The tests include meridional ray contributions to the scattering by tilted solid cylinders and cylindrical shells and Rayleigh wave contributions for steel cubes in water.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123877039","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 critical frequencies for 3, 4 and 5 mm thick flat rectangular mild steel plates of surface areas varying from 0.3 to 3.0 m2 were obtained experimentally using a 120 tonne expanded-metal press. The critical frequencies were noted to increase with decreasing plate thickness and constant for varying perimeter and surface area. The measured values of the critical frequency compared closely with published theoretical data for similar plate parameters.
{"title":"Acoustic Radiation From Mild Steel Plates of Various Thicknesses and Aspect Ratios Excited by a 120 Tonne Press","authors":"D. Eager","doi":"10.1115/imece1999-0228","DOIUrl":"https://doi.org/10.1115/imece1999-0228","url":null,"abstract":"\u0000 The critical frequencies for 3, 4 and 5 mm thick flat rectangular mild steel plates of surface areas varying from 0.3 to 3.0 m2 were obtained experimentally using a 120 tonne expanded-metal press. The critical frequencies were noted to increase with decreasing plate thickness and constant for varying perimeter and surface area. The measured values of the critical frequency compared closely with published theoretical data for similar plate parameters.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127802737","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}
In this paper, the authors describe a numerical truncation technique for handling the numerical instability problems associated with the utilization of the transfer matrix method. This, rather simplistic modification to the numerical coding extends the transfer matrix method to a wide range of applications.
{"title":"Wave Reflection/Transmission Analysis of Thick Multi-Layered Structures Using the Numerical Truncation Approximation for the Transfer Matrix Technique","authors":"K. Balasubramaniam","doi":"10.1115/imece1999-0208","DOIUrl":"https://doi.org/10.1115/imece1999-0208","url":null,"abstract":"\u0000 In this paper, the authors describe a numerical truncation technique for handling the numerical instability problems associated with the utilization of the transfer matrix method. This, rather simplistic modification to the numerical coding extends the transfer matrix method to a wide range of applications.","PeriodicalId":387882,"journal":{"name":"Noise Control and Acoustics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133303113","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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