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An Investigation of the Flow Physics of Acoustic Liners by Direct Numerical Simulation

2018-06-20
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Release : 2018-06-20
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Book Synopsis An Investigation of the Flow Physics of Acoustic Liners by Direct Numerical Simulation by : National Aeronautics and Space Administration (NASA)

Download or read book An Investigation of the Flow Physics of Acoustic Liners by Direct Numerical Simulation written by National Aeronautics and Space Administration (NASA). This book was released on 2018-06-20. Available in PDF, EPUB and Kindle. Book excerpt: This report concentrates on reporting the effort and status of work done on three dimensional (3-D) simulation of a multi-hole resonator in an impedance tube. This work is coordinated with a parallel experimental effort to be carried out at the NASA Langley Research Center. The outline of this report is as follows : 1. Preliminary consideration. 2. Computation model. 3. Mesh design and parallel computing. 4. Visualization. 5. Status of computer code development. 1. Preliminary Consideration. Watson, Willie R. (Technical Monitor) and Tam, Christopher Langley Research Center

A Computational Study of the Flow Physics of Acoustic Liners

2018-06-24
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Release : 2018-06-24
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Book Rating : 965/5 ( reviews)

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Book Synopsis A Computational Study of the Flow Physics of Acoustic Liners by : National Aeronautics and Space Administration (NASA)

Download or read book A Computational Study of the Flow Physics of Acoustic Liners written by National Aeronautics and Space Administration (NASA). This book was released on 2018-06-24. Available in PDF, EPUB and Kindle. Book excerpt: The present investigation is a continuation of a previous joint project between the Florida State University and the NASA Langley Research Center Liner Physics Team. In the previous project, a study of acoustic liners, in two dimensions, inside a normal incidence impedance tube was carried out. The study consisted of two parts. The NASA team was responsible for the experimental part of the project. This involved performing measurements in an impedance tube with a large aspect ratio slit resonator. The FSU team was responsible for the computation part of the project. This involved performing direct numerical simulation (DNS) of the NASA experiment in two dimensions using CAA methodology. It was agreed that upon completion of numerical simulation, the computed values of the liner impedance were to be sent to NASA for validation with experimental results. On following this procedure good agreements were found between numerical results and experimental measurements over a wide range of frequencies and sound-pressure-level. Broadband incident sound waves were also simulated numerically and measured experimentally. Overall, good agreements were also found. Tam, Christopher Langley Research Center

Numerical Simulation of Two-dimensional Acoustic Liners with High Speed Grazing Flow

2009
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Release : 2009
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Book Synopsis Numerical Simulation of Two-dimensional Acoustic Liners with High Speed Grazing Flow by : Qi Zhang

Download or read book Numerical Simulation of Two-dimensional Acoustic Liners with High Speed Grazing Flow written by Qi Zhang. This book was released on 2009. Available in PDF, EPUB and Kindle. Book excerpt:

Numerical Simulation of Acoustic Propagation in a Turbulent Channel Flow with an Acoustic Liner

2018
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Release : 2018
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Book Synopsis Numerical Simulation of Acoustic Propagation in a Turbulent Channel Flow with an Acoustic Liner by : Robin Sebastian

Download or read book Numerical Simulation of Acoustic Propagation in a Turbulent Channel Flow with an Acoustic Liner written by Robin Sebastian. This book was released on 2018. Available in PDF, EPUB and Kindle. Book excerpt: Acoustic liners are a key technology in aeronautics for the passive reduction of the noise generated by aircraft engines. They are employed in a complex flow scenario in which the acoustic waves, the turbulent flow, and the acoustic liner are interacting.During this thesis, in a context of high performance computing, a compressible Navier-Stokes solver has been developed to perform implicit large eddy simulations of a model problem of this interaction: a turbulent plane channel flow with one wall modeled as an impedance condition.As a preliminary step the wall-turbulence in rigid channel flows and associated large-scale motions are investigated. A straightforward algorithm to detect these flow features is developed and the effect of compressibility on the flow structures and their contribution to the drag are studied. Then, the interaction between the acoustic liner and turbulent flow is investigated assuming periodicity in the streamwise direction. It is shown that low resistance and low resonance frequency tend to trigger flow instability, which modifies the conventional wall-turbulence and also results in drag increase.Finally, the simulation of a spatial channel flow was addressed. In this case no periodicity is assumed and an acoustic wave can be injected at the inlet of the domain. The effect of turbulence on sound attenuation is studied without liner, before a liner is introduced on a part of the channel bottom wall. In this more realistic case, it is confirmed that low resistance acoustic liners trigger an instability at the leading edge of the liner, resulting in drag increase and excess noise generation.

Direct Numerical Simulation of Aerodynamic Noise

1989
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Release : 1989
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Book Synopsis Direct Numerical Simulation of Aerodynamic Noise by :

Download or read book Direct Numerical Simulation of Aerodynamic Noise written by . This book was released on 1989. Available in PDF, EPUB and Kindle. Book excerpt: Direct Numerical Simulation of Aerodynamic Noise is a part of an overall research program in compressible turbulence including the study of the physics of compressible turbulence, shock-turbulence interactions, reacting flows with heat release, and aerodynamic sound generation in shear flows. The objective of the work in aerodynamic sound generation is to use direct numerical simulations as a tool to study the noise generation processes directly, specifically answer the following questions: 1. Can one relate particular flow regions and events to the far-field noise? 2. What regions are the dominant contributors to the far-field noise? 3. What is the role played by pairing process in noise generation? 4. How important are the small scales to the noise generation? 5. What processes control the far-field directivity pattern? To answer these questions in shear flows, first study the acoustics of simple building block flows. The discussion below presents recent results obtained for one of the building block flows, the scattering of sound by a vortex. A short discussion of numerical accuracy is also given. Finally, results are presented for aerodynamic sound generation from a 2-d temporal mixing-layer. (jhd).

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