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Publications (94)
The influence of three-dimensional (3D) wind turbine wake effects on sound propagation is investigated. To study this, numerical simulations are conducted using a 3D parabolic equation model at low frequencies, with comparisons made to a two-dimensional (2D) approach that neglects transverse horizontal propagation. Three atmospheric stability condi...
Prediction of the acoustic performance of 3D printed materials is investigated at normal and grazing incidence. A direct numerical (microscopic) simulation that solves the full set of Navier–Stokes equations is used as a reference. It is compared with a macroscopic approach in which the material is represented by an equivalent fluid. The materials...
A coupled approach is proposed for predicting sound radiation from a monopole in arbitrary motion in a moving and inhomogeneous atmosphere. It is based on a heuristic model proposed in the literature for sound radiation by a moving source in a homogeneous atmosphere at rest above an absorbing ground and a ray-tracing code, which takes into account...
Wind turbine noise propagation in a hilly terrain is studied through numerical simulation in different scenarios. Linearized Euler equations are solved in a moving frame that follows the wavefront, and wind turbine noise is modeled with an extended moving source. We employ large-eddy simulations to simulate the flow around the hill and the wind tur...
The propagation of shock waves generated by a transonic flow at the tip of a propeller blade is numerically calculated in order to determine the pressure footprint on an aircraft fuselage. An academic case is first proposed to validate the methodology. An incoming signal is built up as oblique harmonic plane waves. The signal is introduced in the c...
Engineering solutions for the modeling of aircraft noise often rely on simplified approaches that consider quasi-static sources and homogenous propagation conditions. These hypothesis may lead to significant inaccuracies on sound pressure level predictions in certain configurations, especially for source traveling at high mach number and at several...
Wind turbine noise propagation in a hilly terrain is studied through numerical simulation in different scenarios. The linearized Euler equations are solved in a moving frame that follows the wavefront, and wind turbine noise is modeled with an extended moving source. We employ large eddy simulations to simulate the flow around the hill and the wind...
Parabolic equations are among the most popular numerical techniques in many fields of physics. This article considers extra-wide-angle parabolic equations, wide-angle parabolic equations, and narrow-angle parabolic equations (EWAPEs, WAPEs, and NAPEs, respectively) for sound propagation in moving inhomogeneous media with arbitrarily large variation...
Perforated plates experience a nonlinear response at high excitation levels. They are largely used in duct applications , such as aircraft engine nacelles, for which broad-band noise and the presence of flow must be considered. Time-domain methods are well-suited to predict sound propagation under such conditions. Recently, a time-domain admittance...
Noise generated by wind turbines is significantly impacted by its propagation in the atmosphere. Hence, for annoyance issues, an accurate prediction of sound propagation is critical to determine noise levels around wind turbines. This study presents a method to predict wind turbine sound propagation based on linearized Euler equations. We compare t...
Reducing the noise in a duct in the presence of a flow turns out to be a current industrial problem in many engineering applications, such as aircraft engine nacelles, ventilation systems and exhaust pipes. This study aims to analyze nonlinear behavior of absorbent materials used on the duct walls. This research is conducted experimentally through...
Video showing sonic boom propagation over ground profile T2 for (left) the N-wave and (right) the C25D wave.
Video showing sonic boom propagation over ground profile T1 for (left) the N-wave and (right) the C25D wave.
The effect of elevation variation on sonic boom reflection is investigated using real terrain data. To this end, the full two-dimensional Euler equations are solved using finite-difference time-domain techniques. Numerical simulations are performed for two ground profiles of more than 10 km long, extracted from topographical data of hilly regions,...
Wind turbine noise is a significant obstacle to the expansion of wind farms. To understand the generation and propagation of wind turbine noise, various models have been developed in recent years. They are generally used to compute the noise generated by a wind turbine according to its geometry and the characteristics of the surrounding flow, and t...
To study Mars chemistry, SuperCam onboard the NASA Perseverance rover fires bursts of 30 laser shots at rocks. Its microphone records the shock wave generated between 2 and 15 kHz by each laser-induced plasma for distances between 2 m and 8 m, at varying local times, from strong thermal turbulence during daytime, to weaker one at dusk or dawn. In e...
Video showing sonic boom propagation over the urban geometry LCZ 5 for (top) the N-wave and (bottom) the C25D wave.
Video showing sonic boom propagation over the urban geometry LCZ 2 for (top) the N-wave and (bottom) the C25D wave.
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ABSTRACT
Among computational techniques in atmospheric and ocean acoustics and other fields such as seismic wave propagation, the parabolic equation (PE) approach is one of most popular now. The PE is well suited to small computers, large domains, and high frequencies. It can handle many complicated phenomena such as atmospheric an...
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ABSTRACT
A major focus in infrasound research is the inclusion of realistic atmospheric flows in numerical propagation models. This usually encompasses temperature gradients and horizontal wind components, which create atmospheric waveguides. Additionally, gravity waves lead to small-scale variations of the ambient wind in the midd...
Sonic boom propagation over urban areas is studied using numerical simulations based on the Euler equations. Two boom waves are examined: a classical N-wave and a low-boom wave. Ten urban geometries, generated from the local climate zone classification [Stewart and Oke (2012), Bull. Am. Meteorol. Soc. 93(12), 1879–1900], are considered representati...
Video showing the reflection of the N-wave along the hill ground profile using pressure fluctuation maps ([-50;50] Pa), a corresponding wavefront (blue) and wavefronts at other instants in time (dashed black), as well as caustic curves (red).
Video showing the reflection of the N-wave along the terrain depression ground profile using pressure fluctuation maps ([-50;50] Pa), a corresponding wavefront (blue) and wavefronts at other instants in time (dashed black), as well as caustic curves (red).
Video showing the propagation of the N-wave over an isolated building of width Wb=20 m and of height (top) Hb=10 m and (bottom) 40 m.
Video showing the propagation of the N-wave over a periodic urban profile for street widths (top) Ws=10 m, (middle) 20 m, and (bottom) 30 m.
Video showing the propagation of the N-wave in the canyon between the two buildings for street widths (left) Ws=10 m, (middle) 20 m, and (right) 30 m.
Video showing the sonic boom propagation over two buildings separated by a street of width Ws=20 m for (top) the N-wave and (bottom) the C25D wave.
Acceptability of supersonic transportation by population requires an accurate prediction of ground noise levels generated by sonic boom. This study aims at predicting sonic boom propagation over urban areas. For this purpose, numerical simulations are performed; the full 2D Euler equations are solved using high-order finite-difference time-domain t...
A good understanding of wind turbine noise propagation is relevant to better measure the impact of turbines on the environment. In this study, we developed numerical simulations to study the impact of a 2D hill on the sound propagation for a turbine in non flat terrain. The simulations employed a propagation model derived from the linearized Euler...
Thunder initiated from lightnings can be heard up to tens of kilometers, with an acoustic pressure up to several pascals. In real atmospheric conditions, the generation of acoustic waves is conditioned by the electric energy, which is not measurable. The geometry of the strikes, for example their length and curvature, also has a great influence on...
A good understanding of wind turbine noise propagation is relevant to better measure the impact of turbines on the environment. In this study, we developed numerical simulations to study the impact of a 2D hill on the sound propagation for a turbine in non flat terrain. The simulations employed a propagation model derived from the linearized Euler...
The active space is a central bioacoustic concept to understand communication networks and animal behavior. Propagation of biological acoustic signals has often been studied in homogeneous environments using an idealized circular active space representation, but few studies have assessed the variations of the active space due to environment heterog...
Sonic boom reflection is investigated over an isolated building and multiple buildings using numerical simulations. For that, the two-dimensional Euler equations are solved using high-order finite-difference techniques. Three urban geometries are considered for two boom waves, a classical N-wave and a low-boom wave. First, the variations of the pre...
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ABSTRACT
This study aims at analyzing sonic boom reflection over realistic urban areas. For this purpose, numerical simulations are performed. The 2D Euler equations are solved using high-order finite-difference methods, following Emmanuelli et al. [J. Acoust. Soc. Am. 149, 2437–2450 (2021)]. The local climate zone classification o...
The behavior of perforated plates at high excitation level is generally modelled by a surface impedance that depends on the rms velocity in the perforations. A time-domain admittance boundary condition (TDABC) is developed to account for this variation using a multipole model. Two formulations are considered, based on the interpolation either of th...
The expansion of wind farm installations has been hindered by annoyance issues resulting from the noise emitted by wind turbines. Understanding the factors that affect sound propagation is crucial to mitigate the impact of noise. Atmospheric boundary layer (ABL) stratification strongly affects the noise propagation of isolated wind turbines. Howeve...
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ABSTRACT
Acoustic communication networks among birds are widely studied in homogeneous environment like tropical forest or open field. There is no study in heterogeneous environment to our knowledge. However, the propagation of an acoustic signal is strongly influenced by topography, meteorological and ground effects, especially at...
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ABSTRACT
The Plateform of the Laboratory of Studies and Modeling in Acoustics (PLetma) is a suite of scientific softwares developed by the partner institutions of LETMA since 2015. Currently under development, it contains four different models, namely 3D ray-tracing, 3D non-linear one-way equation, 3D normal modes and 2D direct Nav...
This paper aims at improving the weighting function based-method (WFB) for modeling the transient behavior of a laminar flow in cylindrical pipes in a one-dimensional approach. Two improvements for the numerical computation of the unsteady friction term are presented. First, a rational approximation of the weighting function in the Laplace domain i...
![Overpressure waveforms at r=5\documentclass[12pt]{minimal}...](profile/Didier-Dragna/publication/353194719/figure/fig3/AS:1044979422076928@1626153917425/Overpressure-waveforms-at-r5documentclass12ptminimal-usepackageamsmath_Q320.jpg)
Spherical weak blast propagation above a rough periodic surface is investigated by performing numerical simulations of the Euler equations. The study of the reflection pattern shows that waves diffracted by the surface asperities merge to form an effective reflected shock. It is initially detached from the incident shock but gradually catches up wi...
The influence of topography on sonic boom propagation is investigated. The full two-dimensional Euler equations in curvilinear coordinates are solved using high-order finite-difference time-domain techniques. Simple ground profiles, corresponding to a terrain depression, a hill, and a sinusoidal terrain, are examined for two sonic boom waves: a cla...
A general methodology to simulate acoustic propagation in ducts with extended-reacting liners in the time domain is presented, including a generic perforated sheet on the air-material interface. The Linearized Euler Equations (LEE) with a mean flow profile are solved in the duct and the linearized equations on an equivalent fluid are solved in the...
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ABSTRACT
An overview of recent studies on sonic boom reflection over irregular terrain is presented. Numerical simulations based on the two-dimensional Euler equations are performed using high-order finite-difference time-domain techniques, allowing for an accurate prediction of diffraction. Studies are done for two sonic boom wave...
The gradient term suppression (GTS) method for removing the hydrodynamic instability appearing in the time-domain solutions of the linearized Euler equations (LEE) along a lined flow duct is assessed. For this, the characterization of a convective instability in the time domain, with the aid of a complementary modal analysis, is first presented. Th...
A method is presented to characterize general sound-absorbing materials through a pole-based identification of the equivalent fluid. This is accomplished by 1) determining the extended equivalent fluid of the material sample through the transfer function method (TFM), 2) identification of the acoustic response of the material through the poles of t...
The authors have recently shown that irregular reflections of spark-generated pressure weak shocks from a smooth rigid surface can be studied using an optical interferometer [Karzova, Lechat, Ollivier, Dragna, Yuldashev, Khokhlova, and Blanc-Benon, J. Acoust. Soc. Am. 145(1), 26–35 (2019)]. The current study extends these results to the reflection...
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ABSTRACT
The modeling and optimization of acoustic liners under grazing flow is an on-going research topic with applications in the aerospace, automotive and railway industries. Recently, the push for next generation airliners and low-noise ventilation systems further increase the need for innovative configurations with improved br...
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ABSTRACT
Impact of a real terrain on the sonic boom signature at the ground has been little studied in the literature. In the current prediction schemes, a flat and perfectly reflecting ground is usually assumed and the reflected boom is obtained by multiplying the incident boom by a constant factor. In this paper, the effects of a...
This paper investigates the sound fields generated by a source moving horizontally at a constant speed above a non-locally reacting flat ground. The present study offers an extension of an earlier study that focused on sound fields owing to a moving source above a locally reacting ground. However, a locally reacting ground model may not be sufficie...
The irregular reflection of weak acoustic shock waves, known as the von Neumann reflection, has been observed experimentally and numerically for spherically diverging waves generated by an electric spark source. Two optical measurement methods are used: a Mach-Zehnder interferometer for measuring pressure waveforms and a Schlieren system for visual...
Irregular reflection of weak acoustic shock waves occurs under the framework of the von Neumann paradox. In this study, the influence of the surface roughness on the reflection pattern was studied experimentally using spark-generated spherically divergent N-waves of 1.4 cm length reflecting from rigid rough surfaces in air. Dimensions of the roughn...
Characteristics of impulse sounds close to the ground strongly depend on the atmospheric and ground properties in terms of amplitude, shape, and time of arrival. Time-domain numerical modeling is valuable to decipher the interactions between the refractive, scattering and ground effects. A three-dimensional high-order parallel Finite-Difference Tim...
Time-domain simulations are well-suited to study broadband sound propagation. One of the difficulties is the translation of frequency-dependent impedance boundary conditions that leads in the time domain to convolutions. Several methods have been proposed in the literature to have an efficient computation of convolutions. They are based on a multip...
Sound propagation over the ground with a random spatially-varying surface admittance is investigated. Starting from the Green's theorem, a Dyson equation is derived for the coherent acoustic pressure. Under the Bourret approximation, an explicit expression is deduced and an effective admittance that depends on the correlation function of the admitt...
Nonlinear propagation of short N-waves (wavelength of 1.4 cm) through a turbulent layer with outer scale of about 16 cm was simulated based on the 2D parabolic KZK-type equation. A modified von Kármán spectrum was used to generate random fluctuations of wind velocity associated with the presence of turbulence. Statistics of peak overpressure and sh...
Sound characteristics close to the ground strongly depend on the atmospheric and ground properties in terms of amplitude, shape, and time of arrival. Time-domain numerical modeling is able to accurately account for outdoor sound propagation and is valuable to decipher the interactions between the refractive, scattering, and ground effects. It remai...
The acoustic properties of ground surfaces vary in space. Usually, these variations are not accounted for in predictions of outdoor sound propagation for two main reasons. First, they are not known as it is costly to obtain finely sampled spatial measurements of these ground properties. Second, there is no existing simple and quick-to-compute analy...
Irregular reflection ofacoustic weak shockwaves (acoustic Mach numbers less than 0.01) is known as the von Neumann paradox and could not be described by the three-shock theory. In this work, nonlinear reflection regimes were studied experimentally using spark-generated spherically divergent N-waves reflecting from a plane rigid surface. Two optical...
This paper is concerned with the derivation of an analytical solution for the acoustic pressure field generated by a line source moving at a constant speed and height above an absorbing plane and summarizes the results obtained in a recent article [Dragna and Blanc-Benon, J. Sound Vib. 349, 259-275, 2015]. As an extension of previous studies, the f...
Modeling of acoustic propagation in a duct with absorbing treatment is considered. The surface impedance of the treatment is sought in the form of a rational fraction. The numerical model is based on a resolution of the linearized Euler equations by finite difference time domain for the calculation of the acoustic propagation under a grazing flow....
A new broadband impedance eduction method is introduced to identify the surface impedance of acoustic liners from in situ measurements on a test rig. Multimodal acoustic propagation is taken into account in order to reproduce realistic conditions. The present approach is based on the resolution of the linearized 3D Euler equations in the time domai...
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ABSTRACT
Time-domain sound propagation equations in porous media usually involve convolutions, which can be computationally cumbersome. Indeed, a naïve approach would require to store the acoustic variables at every time-step, which would lead to an unacceptable memory space for long range propagation. To reduce the computational b...
The reflection of weak shockwaves on rigid boundaries at grazing angles was studied in different geometrical configurations. It was shown that even in the case of weak shocks, irregular reflection of N-waves can lead to the formation of a three shocks pattern with a Mach stem, a triple point above the rigid surface and an angle reflection which dif...
The study of acoustic shock propagation in complex environments is of great interest for urban acoustics, but also for source localization, an underlying problematic in military applications. To give a better understanding of the phenomenon taking place during the propagation of acoustic shocks, laboratory-scale experiments and numerical simulation...
Although semi-empirical one parameter models are used widely for representing outdoor ground impedance, they are not physically admissible. Even when corrected to satisfy a passivity condition in respect of surface impedance they do not satisfy the condition that the real part of complex density must be greater than zero. Comparison of predictions...
![Figure 1: Sketch of the NASA Langley Grazing Flow Impedance Tube [7]](profile/Renata-Troian/publication/281407249/figure/fig1/AS:613862902603797@1523367729881/Sketch-of-the-NASA-Langley-Grazing-Flow-Impedance-Tube-7_Q320.jpg)
In this study, a broadband impedance eduction method is developed to identify the surface impedance of acoustic liners, mounted in the walls of aircraft engine nacelles, from measurements on a test rig. A numerical model of an acoustic liner under a grazing flow is undertaken by considering finite-difference time-domain simulations and the Euler eq...
An efficient numerical method, referred to as the auxiliary differential equation (ADE) method, is proposed to compute convolutions between relaxation functions and acoustic variables arising in sound propagation equations in porous media. For this purpose, the relaxation functions are approximated in the frequency domain by rational functions. The...
The Fourier pseudospectral time-domain method is an efficient wave-based method to model sound propagation in inhomogeneous media. One of the limitations of the method for atmospheric sound propagation purposes is its restriction to a Cartesian grid, confining it to staircase-like geometries. A transform from the physical coordinate system to the c...
An analytic solution for the problem of sound radiation by a harmonic line source moving at a uniform subsonic speed parallel to an impedance plane is proposed. The main originality of this work is that the variation of the impedance with the frequency is taken into account. Compared to the case of a constant impedance, the reflection coefficient a...
PACS numbers:43.28.Js, 43.28.En, 43.20.El
A time-domain solver of the linearized Euler equations is used to study outdoor propagation of acoustic waves generated by broadband moving sources. For that, high-order schemes, developed initially in the computational aeroacoustics community, are employed. A time-domain impedance boundary condition recent...
CAA based on the Linearised Euler Equations (LEE) is applied to propagate aerodynamic sound over an extended distance including ground effects. The LEE are coupled to data from an LES via an acoustic analogy to follow-up the sound from the source to the extended far field: the complete chain is illustrated on the sound generated by a cylinder in a...
Although time-domain solutions of the linearized Euler equations are well adapted to study the acoustic propagation in an outdoor environment, the modeling of sources in motion in time-domain solvers has not been investigated in the literature yet. This is done here by considering distributed volume sources. First, the influence of the spatial dist...
Conditions for an impedance model to be physically admissible are checked for some popular models in the outdoor sound propagation community. They require that the definition of the impedance model is extended in the whole complex plane and that its inverse Fourier transform is real, causal and passive. For the many impedance models that are writte...
The influence of the ground characteristics and the meteorological conditions on the acoustic propagation of impulse signals above a complex site is studied. For that, numerical simulations using a finite-difference time-domain solver in curvilinear coordinates [Dragna et al., JASA 133(6), 3751-3763 (2013)] are performed. The reference site is a ra...
Results from outdoor acoustic measurements performed in a railway site near Reims in France in May 2010 are compared to those obtained from a finite-difference time-domain solver of the linearized Euler equations. During the experiments, the ground profile and the different ground surface impedances were determined. Meteorological measurements were...
The accuracy of the multi-domain Chebyshev pseudospectral method is investigated for wave propagation problems by examining the properties of the method in the wavenumber space theoretically in terms of dispersion and dissipation errors. For a number of (N + 1) points in the subdomains used in the literature, with N typically between 8 to 32, signi...
The current work aims at developing a linearized Euler equations solver in curvilinear coordinates to account for the effects of topography on sound propagation. In applications for transportation noise, the propagation environment as well as the description of acoustic sources is complex, and time-domain methods have proved their capability to dea...
This paper deals with modeling of sources in motion in time-domain solvers. In the context of transportation noise, acoustic sources are complex. Indeed, they are in motion, and they are generally not compact. Equivalent point sources are often used to simplify the problem. Heuristic methods are then applied to handle acoustic propagation over comp...
Although time-domain solutions of the linearized Euler equations are well adapted to study the acoustic propagation in an outdoor environment, the modeling of sources in motion in time-domain solvers has not been investigated in the literature yet. This is done here by considering distributed volume sources. First, the influence of the spatial dist...
In this work, a numerical model to treat outdoor sound propagation in the time domain is proposed. In the context of railway noise, extended acoustic sources in motion have to be considered. The typical frequency band of interest goes up to 8000 Hz. Finite-Difference Time-Domain(FDTD) methods which are used to solve the linearized Euler equations a...
Finite difference time-domain methods are attractive for the study of broadband outdoor noise propagation, because they can accurately take into account both atmospheric and ground effects. Moreover, these methods allow moving sound sources to be modeled, which can be interesting in the context of transportation noise. A recently proposed method to...
For transportation noise applications, the description of the environment, as well as the description of acoustic sources, is complex; and finite‐difference time‐domain methods have proved their capability to take into account both atmospheric effects and topography. Recently, a time‐domain boundary condition has been proposed [Cotté et al., AIAA J...
Time-domain methods for solving linearized Euler equations have become a new standard in the community of outdoor sound propagation thanks to increased computing power. Indeed, these meth-ods can account for most of the physical phenomena governing atmospheric sound propagation. One of the main issues is still that simulations of long-range propaga...
For transportation noise applications, the description of the environment as well as the description of acoustic sources are complex. Finite-difference time-domain solvers of the linearized Euler equations are well-suited to take into account both atmospheric effects and topography effects. Howeover, it is not straightforward to account for an impe...
La méthode des différences finies dans le domaine temporel (FDTD) est un outil précis et performant pour résoudre leséquationsleséquations d'Euler linéarisées qui gouvernent la propagation acoustiquè a longue distance. Celle-ci permet de prendre en compte précisément les fluctuations locales de vent et de température et aussi des topographies compl...
Finite-difference, time-domain (FDTD) methods are precise and powerful tools to solve linearized Euler equations. Interaction between the acoustic waves with local wind or temperature gradients as well as a complex topography can be taken into account. Recently, a time-domain boundary condition has been proposed [Cotte et al., AIAA J. 47, 2391-2403...
