On Some Fundamental Flaws in Present Aeroacoustic Theory

Fedorchenko, A. T.

doi:10.1006/jsvi.1999.2767

Cited by 29 publications

(32 citation statements)

References 91 publications

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“…Recently, Seasholtz, Panda & Elam (2002) have simultaneously measured the time variation of density and velocity fluctuations in free jets. Earlier efforts that culminated towards the present setup can be found in Seasholtz, Panda & Elam (2001) and Seasholtz & Panda (1999a, 2000. The present setup is for a pointmeasuring system; a continuous wave laser was used, and scattered light from a point on the beam was collected and analyzed.…”

Section: Fundamentals Of Flow Measurement Using Rayleigh Scattering Pmentioning

confidence: 99%

Further Progress in Noise Source Identification in High Speed Jets via Causality Principle

Panda

Seasholtz

Elam³

2003

9th AIAA/CEAS Aeroacoustics Conference and Exhibit

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Section: Fundamentals Of Flow Measurement Using Rayleigh Scattering Pmentioning

confidence: 99%

Further Progress in Noise Source Identification in High Speed Jets via Causality Principle

Panda

Seasholtz

Elam³

2003

9th AIAA/CEAS Aeroacoustics Conference and Exhibit

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“…Entre todos estos problemas el de la reducción de ruido en sistemas de escape de motores de combustión interna está entre los de mayor interés, debido a los cada vez más restrictivos límites de emisión sonora contemplados en la normativa vigente. Existen diversas formas de reducción del ruido total emitido por el flujo de escape de un motor; en opinión de diferentes autores, entre ellos Fedorchenko [63] estas son: (i) cambiar la geometría y estructura de los elementos del sistema, cánulas, o (ii) aplicar algunos dispositivos de control activo, normalmente con el objetivo de actuar sobre los procesos no lineales de inestabilidad hidrodinámica y reducir la intensidad total de la fuente sonora. Pero para la aplicación de cualquiera de estas dos formas de actuación sobre el sistema, así como para el desarrollo de nuevas tecnologías de control, es necesario tener una comprensión teórica de los fenómenos aeroacústicos fundamentales.…”

Section: Evolución Históricaunclassified

“…De acuerdo con los comentarios realizados por Fedorchenko [63] en relación a los puntos débiles de la teoría de Lighthill descrita anteriormente, podemos destacar las siguientes críticas. En primer lugar en relación a la aproximación realizada por Lighthill en su ecuación de propagación sonora de acuerdo con la expresión…”

Section: Análisis Crítico De La Analogía De Lighthillunclassified

“…Así, por ejemplo Crighton [32], dice que 'la teoría de Lighthill ha sido a distancia la más exitosa y versátil'; de modo similar Ffowcs Williams [64] comenta que 'la teoría de Lighthill fue una obra maestra'. En esta misma línea Crow [63] menciona, a modo de apoyo a dicha teoría, que ninguna de las descripciones físicas alternativas de modelos de fuentes sonoras aerodinámicas ha sido capaz de competir con la teoría de Lighthill. En este sentido, se puede considerar que este modelo proporciona una descripción válida del problema del sonido generado por un flujo incompresible.…”

Section: Análisis Crítico De La Analogía De Lighthillunclassified

“…De cualquier forma, una de las cuestiones más relevantes con respecto a este tema, es si u I puede atribuirse solamente al campo sonoro, y u s al flujo de fondo. Ciertamente, en general, la velocidad del flujo de fondo puede descomponerse como suma de componentes irrotacional y solenoidal, y la velocidad del campo acústico puede dividirse de modo similar, como corrobora Fedorchenko [63]. Además, algunos autores como Crow [114] mostraron que las fluctuaciones de presión asociadas a cambios en el campo solenoidal podían propagarse al campo irrotacional como sonido.…”

Section: Descomposición Del Campo De Velocidades Del Fluidounclassified

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Contribución al estudio y caracterización de la generación de ruido de flujo en el sistema de escape.

Verdú¹,

Concepción²

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The studies of the vehicle noise emissions has been acquired a great relevance over the last few years for two reasons: (1) the increased social sensitivity to environmental contamination phenomena among which acoustic contamination is found, and (2) to the highest market requirements (higher "capability"vehicles at the same time as more comfortable ones: acoustic comfort).Within the complexity of the vehicle acoustic generation phenomena in this doctoral thesis, we will focus on one of the engine contributions: the exhaust noise. This component of noise is the result of two different phenomena: pulsating noise originated in the gas exchange process in the cylinders, and the flow noise induced by the turbulence phenomena developed by the mean flow that goes through the exhaust system. From these two phenomena the core of our study is flow noise and its prediction, under the motivation that as well as the pulsating noise being extensively studied and there being some prediction methods in it, the flow noise is unknown to a great extent. To this we should add, that while the pulsating noise contribution, main source, has been reduced the flow noise contribution has become more and more important in exhaust noise. The relevance of flow noise contribution is associated with its interaction with the acoustics in the system (it could amplify the main source contribution) and the existence of mufflers that work as flow noise generation sources.For the flow noise contribution study, the present doctoral thesis has been structured in six well-defined chapters.In the first chapter there is a summary of the different contributions that can be distinguished in the overall vehicle emitted noise. The importance of the flow noise study is justified from the present state of knowledge in this subject, and also the methodology bases used to perform it.In the second chapter, an experimental procedure for the estimation of the volume velocity fluctuation at the open end of the exhaust tailpipe of an internal combustion engine is presented. The different physical mechanisms involved in the emission process are analysed through the introduction of a realistic emission model. The possibility to consider that the pulsating component of the noise and the flow noise are decoupled to a certain extent is established, which means that this last component is generated by a mean "steady" flow superimposed to a pulsating flow. 8Once the possibility of studying the contribution of flow noise generated during the exhaust process as a steady flow effect has been justified. In the third chapter an experimental technique, sound intensity from in-duct measurements, is presented to analyse it. This technique allows the study of the flow noise generation by the individual component of an exhaust system (useful in the automotive industry) on a cold flow test bench. The proposed technique also allows to separate and to know the contributions in the final radiated noise of the internal and external sources of the muffler.Once the experimental pr...

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A Primitive Approach to Aeroacoustics

Hirschberg

Schram

2002

Lecture Notes in Physics

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On Some Fundamental Flaws in Present Aeroacoustic Theory

Cited by 29 publications

References 91 publications

Further Progress in Noise Source Identification in High Speed Jets via Causality Principle

Further Progress in Noise Source Identification in High Speed Jets via Causality Principle

Contribución al estudio y caracterización de la generación de ruido de flujo en el sistema de escape.

A Primitive Approach to Aeroacoustics

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