An Investigation Of The Flow Physics Of Acoustic Liners By Direct Numerical Simulation
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Author | : National Aeronautics and Space Administration (NASA) |
Publisher | : Createspace Independent Publishing Platform |
Total Pages | : 24 |
Release | : 2018-06-20 |
Genre | : |
ISBN | : 9781721601707 |
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
Author | : National Aeronautics and Space Administration (NASA) |
Publisher | : Createspace Independent Publishing Platform |
Total Pages | : 24 |
Release | : 2018-06-24 |
Genre | : |
ISBN | : 9781721832965 |
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
Author | : Qi Zhang |
Publisher | : |
Total Pages | : 150 |
Release | : 2009 |
Genre | : |
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Author | : Robin Sebastian |
Publisher | : |
Total Pages | : 0 |
Release | : 2018 |
Genre | : |
ISBN | : |
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.
Author | : |
Publisher | : |
Total Pages | : 39 |
Release | : 1989 |
Genre | : |
ISBN | : |
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).
Author | : National Aeronautics and Space Administration (NASA) |
Publisher | : Createspace Independent Publishing Platform |
Total Pages | : 34 |
Release | : 2018-06-30 |
Genre | : |
ISBN | : 9781722116750 |
The acoustic radiation from isotropic turbulence is computed numerically. A hybrid direct numerical simulation approach which combines direct numerical simulation (DNS) of the turbulent flow with the Lighthill acoustic analogy is utilized. It is demonstrated that the hybrid DNS method is a feasible approach to the computation of sound generated by turbulent flows. The acoustic efficiency in the simulation of isotropic turbulence appears to be substantially less than that in subsonic jet experiments. The dominant frequency of the computed acoustic pressure is found to be somewhat larger than the dominant frequency of the energy-containing scales of motion. The acoustic power in the simulations is proportional to epsilon (M(sub t))(exp 5) where epsilon is the turbulent dissipation rate and M(sub t) is the turbulent Mach number. This is in agreement with the analytical result of Proudman (1952), but the constant of proportionality is smaller than the analytical result. Two different methods of computing the acoustic power from the DNS data bases yielded consistent results. Sarkar, S. and Hussaini, M. Y. Langley Research Center NAS1-19480; RTOP 505-90-52-01...
Author | : Doyle Knight |
Publisher | : Springer Science & Business Media |
Total Pages | : 516 |
Release | : 2012-12-06 |
Genre | : Technology & Engineering |
ISBN | : 940114513X |
This collection of papers presents a broad range of topics in DNS and LES, from new developments in LES modeling to DNS and LES for supersonic and hypersonic boundary layers. The book provides an extensive view of the state of the art in the field.
Author | : J.F. Allard |
Publisher | : Springer Science & Business Media |
Total Pages | : 296 |
Release | : 2012-12-06 |
Genre | : Technology & Engineering |
ISBN | : 9401118663 |
This book has grown out of the research activities of the author in the fields of sound propagation in porous media and modelling of acoustic materials. It is assumed that the reader has a background of advanced calculus, including an introduction to differential equations, complex variables and matrix algebra. A prior exposure to theory of elasticity would be advantageous. Chapters 1-3 deal with sound propagation of plane waves in solids and fluids, and the topics of acoustic impedance and reflection coefficient are given a large emphasis. The topic of flow resistivity is presented in Chapter 2. Chapter 4 deals with sound propagation in porous materials having cylindrical pores. The topics of effective density, and of tortuosity, are presented. The thermal exchanges between the frame and the fluid, and the behaviour of the bulk modulus of the fluid, are described in this simple context. Chapter 5 is concerned with sound propagation in other porous materials, and the recent notions of characteristic dimensions, which describe thermal exchanges and the viscous forces at high frequencies, are introduced. In Chapter 6, the case of porous media having an elastic frame is considered in the context of Biot theory, where new topics described in Chapter 5 have been included.
Author | : American Institute of Aeronautics and Astronautics |
Publisher | : |
Total Pages | : 954 |
Release | : 2004 |
Genre | : Aeronautics |
ISBN | : |
Author | : |
Publisher | : |
Total Pages | : 464 |
Release | : 1995 |
Genre | : Aeronautics |
ISBN | : |