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Proceedings ArticleDOI

Model for the Control of Sound Radiation from an Aircraft Panel Excited by a Turbulent Boundary Layer Using Impedance Control

10 May 1999-
TL;DR: In this paper, a model of an aircraft panel excited by a Turbulent Boundary Layer (TBL) and radiating sound into an interior space that is modifled by the addition of discrete mechanical impedances is presented.
Abstract: This paper describes a model of an aircraft panel excited by a Turbulent Boundary Layer (TBL) and radiating sound Into an interior space that is modifled by the addition of discrete mechanical impedances. The effect of these impedance control devices is to modify the modal mobility of the panel. The radiation of sound from the panel can be expressed as a function of the attached impedances and the impedance can be optimized so as to reduce the sound radiating from the panel. Several potential mechanisms of control are identifled.
Citations
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Journal ArticleDOI
TL;DR: In this article, the effect of the finite impedance not only to the acoustical effect but also to the hydrodynamic effects were examined in a wind tunnel experiment on aero-acoustical effects of finite surface impedance on low Mach number flow around a circular cylinder.
Abstract: This paper describes a wind tunnel experiment on aero-acoustical effect of finite surface impedance on low Mach number (Ma) flow around a circular cylinder. Modification of surface acoustical properties of source area is said to result in reduction of radiated sound pressure level. In this paper the effect of the finite impedance not only to the acoustical effect but also to the hydrodynamic effects were examined. Three boundary conditions (BC) of surface impedance were supposed: 1) rigid surface, 2) uniform and 3) optimized impedance distribution by introducing an array of micro-scale perforation with a back space. A wind tunnel experiment was conducted according to the three types of BC with three different experimental models under the Reynolds number (Re) condition from 6 000 to 12 000. The third condition caused reduction of the far field pressure level by 6 dB at largest case compared to the first condition.

13 citations

Journal ArticleDOI
TL;DR: In this paper, a mathematical formulation and numerical implementation on the effect of surface impedance for reducing aerodynamic sound radiated from a circular cylinder is described, and a new approach of optimized surface impedance, inducing flow by a Helmholtz resonator is proposed.
Abstract: This paper describes a mathematical formulation and numerical implementation on the effect of surface impedance for reducing aerodynamic sound radiated from a circular cylinder. Firstly, mathematical derivation of the ideal surface impedance that eliminates the pressure fluctuation on the body surface, utilizing the Green's function, is discussed. Secondly, a numerical simulation is explained with using the Large Eddy Simulation (LES) techniques at Reynolds number 3000, with boundary conditions of, (i) rigid, (ii) finite uniform impedance, and (iii) our new approach of optimized surface impedance, inducing flow by a Helmholtz resonator. In the simulation only larger impedance than the ideal one is applied to the surface due to computational instability which restrains the lower limit of impedance. The effect of optimized surface impedance is verified by the simulation via the fact that the amplitude of the surface pressure fluctuation decreases remarkably.

6 citations

Book
29 Jul 2013
TL;DR: The work conducted by the Structural Acoustics Integrated Technology Development (ITD) Team under NASA's High Speed Research (HSR) Phase II program from 1993 to 1999 is summarized in this article.
Abstract: This report summarizes the work conducted by the Structural Acoustics Integrated Technology Development (ITD) Team under NASA's High Speed Research (HSR) Phase II program from 1993 to 1999. It is intended to serve as a reference for future researchers by documenting the results of the interior noise and sonic fatigue technology development activities conducted during this period. For interior noise, these activities included excitation modeling, structural acoustic response modeling, development of passive treatments and active controls, and prediction of interior noise. For sonic fatigue, these activities included loads prediction, materials characterization, sonic fatigue code development, development of response reduction techniques, and generation of sonic fatigue design requirements. Also included are lessons learned and recommendations for future work.

2 citations

References
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01 Jan 1994
TL;DR: The Diskette v 2.06, 3.5''[1.44M] for IBM PC, PS/2 and compatibles [DOS] Reference Record created on 2004-09-07, modified on 2016-08-08.
Abstract: Note: Includes bibliographical references, 3 appendixes and 2 indexes.- Diskette v 2.06, 3.5''[1.44M] for IBM PC, PS/2 and compatibles [DOS] Reference Record created on 2004-09-07, modified on 2016-08-08

19,881 citations

Book
13 May 1980
TL;DR: This chapter discusses single-Input/Single-Output Relationships, nonstationary data analysis techniques, and procedures to Solve Multiple- Input/Multiple-Output Problems.
Abstract: Discusses engineering applications and recent developments based upon correlation and spectral analysis. Illustrations deal with applications to acoustics, mechanical vibrations, system identification, and fluid dynamics problems in aerospace, automotive, industrial noise control, civil engineering and oceanographic fields, as well as similar problems in other fields. Tackles problems and solutions, assuming reader has required hardware and software to compute estimates of correlation, spectra, coherence, and phase functions.

2,447 citations

Journal ArticleDOI
TL;DR: In this article, the effects of dynamic coupling between a structure and an electrical network through the piezoelectric effect are derived. But the authors focus on the case of a cantilevered beam with surface mounted piezoceramics and indirect voltage and current drive.
Abstract: The paper models the effects of dynamic coupling between a structure and an electrical network through the piezoelectric effect. The coupled equations of motion of an arbitrary elastic structure with piezoelectric elements and passive electronics are derived. State space models are developed for three important cases: direct voltage driven electrodes, direct charge driven electrodes, and an indirect drive case where the piezoelec tric electrodes are connected to an arbitrary electrical circuit with embedded voltage and current sources. The equations are applied to the case of a cantilevered beam with surface mounted piezoceramics and indirect voltage and current drive. The theoretical derivations are validated experimentally on an actively controlled cantilevered beam test article with indirect voltage drive.

715 citations

Journal ArticleDOI
TL;DR: In this paper, the authors discussed the statistical properties of the pressure field at the wall of turbulent attached shear flows and discussed the appropriate scale of the measured pressure field and its properties.
Abstract: The paper is discussion of measurements of the statistical properties of the pressure field at the wall of turbulent attached shear flows. These measurements have been made only in part by the author. A preliminary discussion is given of the important limitations imposed by the imperfect space resolution of contemporary pressure transducers. There follows a discussion of the appropriate scales of the pressure field. It is shown that measurements of the longitudinal cross-spectral densities lead to similarity variables for the space-time covariance of the pressure and for the corresponding spectra. The existence of these similarity variables may be due to the dispersion of the sources of pressure by the mean velocity gradient. Such a mechanism is illustrated by a simple model. Lateral cross-spectral densities also lead approximately to similarity variables.Computations based directly upon detailed pressure-velocity correlation measurements by Wooldridge & Willmarth reveal that an important part of the pressure at the wall of a boundary layer is contributed by source terms which are quadratic in the turbulent velocity fluctuations; the interaction of the mean strain rate with normal velocity fluctuations, being in effect limited to a region very near the wall, supplies a dominant contribution only at high frequencies and its scales, downstream convective speed and convective memory are markedly smaller than those of the observed wall pressure.The inner part of the Law of the Wall region (y* [les ] 100) seems to be substantially free of pressure sources and within that region (a) the pressure can be given in terms of its boundary value, and (b) the local velocity field is dependent upon but unbale to affect appreciably the turbulent pressures.

568 citations

Journal ArticleDOI
TL;DR: It is found that, for the structural and boundary layer parameters typical of transport aircraft, the contributions of resonant, acoustically inefficient plate modes dominate the radiated power.

240 citations