Perturbed Compressible Equations for Aeroacoustic Noise Prediction at Low Mach Numbers

Seo, Jung-Hee; Moon, Young J.

doi:10.2514/1.3001

Cited by 88 publications

(62 citation statements)

References 15 publications

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“…To reduce the growth of hydrodynamic instabilities, some other modifications of the original splitting method were proposed by Ewert and Schro¨der 19 and Seo and Moon. 20 The work carried out by Shen and colleagues [21][22][23][24] was based on full numerical simulations, with acoustic equations derived directly from the original compressible Navier-Stokes equations. This method is referred to as the flow/acoustic splitting technique.…”

Section: Introductionmentioning

confidence: 99%

Improvement of airfoil trailing edge bluntness noise model

Zhu

Shen

Sørensen

et al. 2016

Advances in Mechanical Engineering

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In this article, airfoil trailing edge bluntness noise is investigated using both computational aero-acoustic and semiempirical approach. For engineering purposes, one of the most commonly used prediction tools for trailing edge noise are based on semi-empirical approaches, for example, the Brooks, Pope, and Marcolini airfoil noise prediction model developed by Brooks, Pope, and Marcolini (NASA Reference Publication 1218, 1989). It was found in previous study that the Brooks, Pope, and Marcolini model tends to over-predict noise at high frequencies. Furthermore, it was observed that this was caused by a lack in the model to predict accurately noise from blunt trailing edges. For more physical understanding of bluntness noise generation, in this study, we also use an advanced in-house developed high-order computational aero-acoustic technique to investigate the details associated with trailing edge bluntness noise. The results from the numerical model form the basis for an improved Brooks, Pope, and Marcolini trailing edge bluntness noise model.

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Section: Introductionmentioning

confidence: 99%

Improvement of airfoil trailing edge bluntness noise model

Zhu

Shen

Sørensen

et al. 2016

Advances in Mechanical Engineering

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“…Details of this approach can be found in [8,9]. Following this idea, consider a fluid particle which has physical properties:…”

Section: Fundamental Assumptions and Equationsmentioning

confidence: 99%

“…Many different models have been proposed and used in these applications, such as direct numerical methods [1], the linearized Euler equations (LEE) [2], acoustic analogy methods (Lighthill's acoustic analogy theory [3], Ffowcs-Williams and Hawkings (FW-H) method [4], etc…), and hydrodynamic/acoustic splitting methods (expansion around an incompressible flow (EIF) model [5,6], acoustic perturbation equations (APE) [7,8], perturbed compressible equations (PCE) [9,10], etc...).…”

Section: Introductionmentioning

confidence: 99%

“…The purpose of our work is to devise a Lagrangian approach for computational acoustics, which computes the fluid particle motion and the sound waves based on the acoustic perturbation assumption [8,9]. In this way, this approach can consider sound generation and propagation with complex background flow or multiple media, and can be more efficient than the Lagrangian DNS method by ignoring scale disparities since the flow and acoustics are treated separately [10,28] as in hydrodynamic/acoustic splitting methods.…”

Section: Introductionmentioning

confidence: 99%

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A Lagrangian Approach for Computational Acoustics with Meshfree Method

Zhang

Smith

Zhang

et al. 2017

Preprint

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Abstract:Although Eulerian approaches are standard in computational acoustics, they are less effective for certain classes of problems like bubble acoustics and combustion noise. A different approach for solving acoustic problems is to compute with individual particles following particle motion. In this paper, a Lagrangian approach to model sound propagation in moving fluid is presented and implemented numerically, using three meshfree methods to solve the Lagrangian acoustic perturbation equations (LAPE) in the time domain. The LAPE split the fluid dynamic equations into a set of hydrodynamic equations for the motion of fluid particles and perturbation equations for the acoustic quantities corresponding to each fluid particle. Then, three meshfree methods, the smoothed particle hydrodynamics (SPH) method, the corrective smoothed particle (CSP) method, and the generalized finite difference (GFD) method, are introduced to solve the LAPE and the linearized LAPE (LLAPE). The SPH and CSP methods are widely used meshfree methods, while the GFD method based on the Taylor series expansion can be easily extended to higher orders. Applications to modeling sound propagation in steady or unsteady fluids in motion are outlined, treating a number of different cases in one and two space dimensions. A comparison of the LAPE and the LLAPE using the three meshfree methods is also presented. The Lagrangian approach shows good agreement with exact solutions. The comparison indicates that the CSP and GFD method exhibit convergence in cases with different background flow. The GFD method is more accurate, while the CSP method can handle higher Courant numbers.

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“…Several non-radiating base flow have been suggested in the literature, e.g. incompressible flows by the viscous/acoustic splitting method in [HP94], [SS99], [SM05] and [SM06] and time averaged flows by the linearised Euler equations (LEE) and modifications in [BBJ02] and [ES03], but fail at least in one of the following points:…”

Section: ]mentioning

confidence: 99%

Separation of acoustic waves in isentropic flow perturbations

Henke

2014

The Journal of the Acoustical Society of America

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Abstract:The present contribution investigates the mechanisms of sound generation and propagation in the case of highly-unsteady flows. Based on the linearisation of the isentropic Navier-Stokes equation around a new pathlineaveraged base flow, it is demonstrated for the first time that flow perturbations of a non-uniform flow can be split into acoustic and vorticity modes, with the acoustic modes being independent of the vorticity modes. Therefore, we can propose this acoustic perturbation as a general definition of sound. As a consequence of the splitting result, we conclude that the present acoustic perturbation is propagated by the convective wave equation and fulfils Lighthill's acoustic analogy. Moreover, we can define the deviations of the Navier-Stokes equation from the convective wave equation as "true" sound sources. In contrast to other authors, no assumptions on a slowly varying or irrotational flow are necessary. Using a symmetry argument for the conservation laws, an energy conservation result and a generalisation of the sound intensity are provided.

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Perturbed Compressible Equations for Aeroacoustic Noise Prediction at Low Mach Numbers

Cited by 88 publications

References 15 publications

Improvement of airfoil trailing edge bluntness noise model

Improvement of airfoil trailing edge bluntness noise model

A Lagrangian Approach for Computational Acoustics with Meshfree Method

Separation of acoustic waves in isentropic flow perturbations

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