Numerical Simulation Of Acoustic Propagation In A Turbulent Channel Flow With An Acoustic Liner
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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 | : Christophe Brun |
Publisher | : Springer Science & Business Media |
Total Pages | : 344 |
Release | : 2009-03-07 |
Genre | : Technology & Engineering |
ISBN | : 3540899561 |
Large Eddy Simulation (LES) is a high-fidelity approach to the numerical simulation of turbulent flows. Recent developments have shown LES to be able to predict aerodynamic noise generation and propagation as well as the turbulent flow, by means of either a hybrid or a direct approach. This book is based on the results of two French/German research groups working on LES simulations in complex geometries and noise generation in turbulent flows. The results provide insights into modern prediction approaches for turbulent flows and noise generation mechanisms as well as their use for novel noise reduction concepts.
Author | : Nishant Kumar Singh |
Publisher | : |
Total Pages | : |
Release | : 2012 |
Genre | : |
ISBN | : |
This research involves study of acoustic propagation of pulse in a simple expansion muffler, which is very often used in HVAC or automotive exhausts. A hybrid pressure-based compressible solver is developed and validated for a low Mach number flow simulation of acoustic pulse. This new solver is developed using C++ based OpenFOAM toolkit and further tested for low Mach number flow test case. The analysis of simple expansion muffler for various structures, frequency ranges and numerical schemes is performed and results are summarized. RANS simulation of duct and muffler with mean flow is conducted and results are presented with inherent limitations associated with the method. Further, a mixed synthetic inflow boundary condition is also developed and validated for LES of channel flow. The mixed synthetic boundary is then used for LES of a simple expansion muffler to analyse the flow-acoustic and acoustic-pulse interactions inside the expansion muffler. The improvement in the prediction of tonal noise and vortex shedding inside the chamber is highlighted in comparison to the RANS method. Further, the effect of forced pulsation on flow-acoustic is observed in regard to the shift in Strouhal number inside the simple expansion muffler. Finally, a set of benchmark results for experimental analysis of the simple expansion muffler both, with and without flow is obtained to compare attenuation in forced pulsation for various mean-flow velocities. These experimental results are then used for validation of the proposed pressure-based compressible solver.
Author | : Kenneth J. Baumeister |
Publisher | : |
Total Pages | : 60 |
Release | : 1973 |
Genre | : Airplanes |
ISBN | : |
A finite difference formulation is presented which is useful in the study of acoustically treated inlet and exhaust ducts used in turbofan engines. The difference formulation can readily handle acoustic flow field complications, such as axial variations in wall impedance and cross-sectional area, that would occur in a sonic inlet. In formulating the difference solutions, the continuous acoustic field is lumped into a series of grid points spread uniformly throughout the field. At each point, the pressure is separated into its real and imaginary terms. Example solutions are presented for sound propagation in a one-dimensional straight hard-wall duct and in a two-dimensional straight soft-wall duct without steady flow.
Author | : Qi Zhang |
Publisher | : |
Total Pages | : 150 |
Release | : 2009 |
Genre | : |
ISBN | : |
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 | : William Roberto Wolf |
Publisher | : Stanford University |
Total Pages | : 238 |
Release | : 2011 |
Genre | : |
ISBN | : |
The development of physics-based noise prediction tools for analysis of aerodynamic noise sources is of paramount importance since noise regulations have become more stringent. Direct simulation of aerodynamic noise remains prohibitively expensive for engineering problems because of the resolution requirements. Therefore, hybrid approaches that consist of predicting nearfield flow quantities by a suitable CFD simulation and farfield sound radiation by aeroacoustic integral methods are more attractive. In this work, we apply the fast multipole method (FMM) to accelerate the solution of boundary integral equation methods such as the boundary element method (BEM) and the Ffowcs Williams & Hawkings (FWH) acoustic analogy formulation. The FMM-BEM is implemented for the solution of acoustic scattering problems and the effects of non-uniform potential flows on acoustic scattering are investigated. The FMM-FWH is implemented for the solution of two and three-dimensional problems of sound propagation. The effects of flow convection and non-linear quadrupole sources are assessed through the study of sound generated by unsteady laminar flows. Finally, a hybrid methodology is applied for the investigation of airfoil noise. This study is important for the design of aerodynamic shapes such as wings and high-lift devices, as well as wind turbine blades, fans and propellers. The present investigation of airfoil self-noise generation and propagation concerns the broadband noise that arises from the interaction of turbulent boundary layers with the airfoil trailing edge and tonal noise that arises from vortex shedding generated by laminar boundary layers. Nearfield acoustic sources are computed using compressible large eddy simulation (LES) and acoustic predictions are performed by the FMM-FWH. Numerical simulations are conducted for a NACA0012 airfoil with tripped boundary layers and blunt rounded trailing edge at different Mach numbers and angles of incidence. The effects of non-linear quadrupole sources and convection are assessed. In order to validate the numerical solutions, flow simulation and acoustic prediction results are compared to experimental data available in the literature and excellent agreement is observed.
Author | : Mark Wochner |
Publisher | : |
Total Pages | : |
Release | : 2006 |
Genre | : |
ISBN | : |
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 | : Roberto Camussi |
Publisher | : Springer Science & Business Media |
Total Pages | : 453 |
Release | : 2013-02-11 |
Genre | : Technology & Engineering |
ISBN | : 3709114586 |
The articles in this volume present the state-of-the-art in noise prediction, modeling and measurement. The articles are partially based on class notes provided during the course `Noise sources in turbulent shear flows', given at CISM on April 2011. The first part contains general concepts of aero acoustics, including vortex sound theory and acoustic analogies, in the second part particular emphasis is put into arguments of interest for engineers and relevant for aircraft design: jet noise, airfoil broadband noise, boundary layer noise (including interior noise and its control) and the concept of noise sources, their theoretical modeling and identification in turbulent lows. All these arguments are treated extensively with the inclusion of many practical examples and references to engineering applications.