Michel Tournour

Michel Tournour
Independent Researcher

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76
Publications
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907
Citations

Publications

Publications (76)
Conference Paper
Full-text available
A boundary element formulation is used in order to solve acoustic wave propagation in non-uniform potential subsonic mean flows. An approach based on a Taylor--Lorentz variable transformation is proposed for low Mach number mean flows. The variable transformation reduces an approximate formulation of the linearised potential wave equation to the st...
Conference Paper
The recently concluded EC FP7 IDEALVENT project has seen the application of a variety of simulation methods by the consortium partners to an industrial blower unit such as used in aircraft Environmental Control Systems. The blower was subjected to different inflow conditions in order to better comprehend the importance of installation effects, and...
Article
Shell-like structures are common in many engineering applications and composite materials and laminated sandwich are being used as a viable lightweight alternative to standard engineering materials. Simulations of multilayer structures often require explicit modelling in the through-the-thickness direction to account for properties discontinuities,...
Article
An integral formulation for acoustic radiation in moving flows is presented. It is based on a potential formulation for acoustic radiation on weakly non-uniform subsonic mean flows. This work is motivated by the absence of suitable kernels for wave propagation on non-uniform flow. The integral solution is formulated using a Green's function obtaine...
Conference Paper
Full-text available
A boundary element method in a transformed Taylor-Lorentz space-time is presented to solve sound propagation and scattering in weakly non-uniform subsonic potential flows. Boundary element solutions are conventionally provided for sound propagation and scattering in quiescent media. On the other hand, an effective approach to solve wave propagation...
Article
Full-text available
Manufacturing processes are often considered the final stage of the design. As a matter of fact, it is during the manufacturing that material properties are ultimately determined. This is especially true for composite materials, whose manufacturing processes are often lowly automated and thus subject to the low repeatability of manual operations. M...
Article
Full-text available
This paper presents an efficient approach for computing frequency sweeps with fine increments of acoustic systems described by the variational indirect boundary element method. The matrices arising from such boundary element discretizations are fully populated and their assembly is computationally demanding as it involves the calculation of double...
Conference Paper
Full-text available
A combined Helmholtz integral equation formulation (CHIEF) for wave propagation in a weakly non-uniform subsonic potential mean flow is presented. This approach allows the irregular frequency issue, affecting boundary element solutions of external noise propagation, to be overcome. The CHIEF method is a well-established approach for low-frequency l...
Chapter
Full-text available
The effective treatment of unbounded problems remains a major challenge in the field of numerical acoustics. Domain-based methods like the Finite Element method, which is investigated here, cannot directly handle such problems. To limit the size of the computational region, an artificial truncation must be used at some point on which a dedicated ra...
Article
Composite and sandwich structures are appealing to many engineering fields. Despite the increased rate of application, their cost remains higher compared to traditional engineering materials. One of the reasons is the necessary use of experimental characterization and validation of materials and structures respectively. One way to reduce costs is t...
Article
Full-text available
An integral formulation for acoustic radiation in moving flows is presented. It is based on a potential formulation for acoustic radiation on weakly non-uniform subsonic mean flows. This work is motivated by the absence of suitable kernels for wave propagation on non-uniform flow. The integral solution is formulated using a Green's function obtaine...
Article
The present review aims at gathering the available literature on damping in composite materials. A chronological review of test methods for damping estimation is presented in order to describe the time-line of the theoretical knowledge development in this field. In the last years many new material configurations have emerged that deserve investigat...
Conference Paper
Shell-like structures are common in many engineering applications such as aerospace structures, civil constructions and automotive components. In all these fields, composite materials and laminated sandwich are used as a viable lightweight alternative to standard engineering materials. Simulations of multilayer structures often require explicit mod...
Conference Paper
Full-text available
The focus of this study is to present the limitations of a hybrid numerical method for the prediction of sound propagation and scattering within an unbounded domain. We present a combined Finite Element Method (FEM)/Radiating-surface approach based on a Kirchhoff's integral formulation with a mean flow. This work identifies the sources of numerical...
Conference Paper
Full-text available
This paper presents a new simplied approach for the prediction of the acoustic shielding from lifting bodies by means of a nite element method. It extends a method already validated for aerodynamic applications to Aeroacoustics on the basis of the small perturbation expansion. A numerical model to represent the eect of the circulation developed by...
Conference Paper
Full-text available
Trim materials are designed to minimize sound transmission and maximize sound absorption. Often, a bal-ance between those two quantities is desired with an emphasis on one or another depending on the application in hand. Porous material are typically used as they allow for both sound absorption and transmission loss while minimizing the added mass....
Conference Paper
Trim materials are designed to minimize sound transmission and maximize sound absorption. Often, a balance between those two quantities is desired with an emphasis on one or another depending on the application in hand. Porous material are typically used as they allow for both sound absorption and transmission loss while minimizing the added mass....
Conference Paper
Trim materials are designed to minimize sound transmission and maximize sound absorption. Often, a balance between those two quantities is desired with an emphasis on one or another depending on the application in hand. Porous material are typically used as they allow for both sound absorption and transmission loss while minimizing the added mass....
Conference Paper
Full-text available
NVH behaviour of composite structures has lately become a concern for aerospace and automotive industries. The application of standard absorbing treatments at the end of the design stage heavily impacts the modal characteristics of components. Much effort is thus dedicated to understand which parameters play a role in the stiffness and damping prop...
Article
This paper reports on the numerical simulations of the sound field around a simplified locomotive at 1/16 scale in semi-anechoic field and the comparison with experiment data. Sources mimicking the fans or the air-inlet grids are located either on the top or on the sides of the mock-up locomotive. A reflecting ground and an optional vertical rigid...
Article
A novel semi-analytical model based on Amiet's theory is proposed to predict the scattered acoustic field related to turbulence-interaction noise. The simulated scattered acoustic field is compared to the corresponding measurements of a stationary airfoil in a turbulent stream for validation purposes. The paper is composed of three main parts, wher...
Article
Broadband noise generated by a low-speed industrial axial fan and its scattered field by a benchmark obstacle have been addressed. Amiet’s theory on turbulence-interaction noise has been extended in order to predict the acoustic response of a fan in its geometrical near-field. A segmentation technique has been applied for spanwise varying flow cond...
Conference Paper
Full-text available
In the context of automotive NVH applications, the deterministic element-based approaches such as Finite Element (FE) and Boundary Element (BE) methods have become the " default " tools for virtual performance assessment. Notwithstanding their flexibility and widespread use, the application range of these methods is limited to low-frequency applica...
Conference Paper
Nowadays, deterministic Computer Aided Engineering (CAE) methods are well established to support the mechanical product industry. A key challenge is to ensure the vibro-acoustic performance when addressing mid- and even high-frequency regimes. New numerical acoustic solvers are required in order to achieve the necessary calculations for large-scale...
Conference Paper
This paper deals with the analytical and experimental modeling of the broadband noise generated by a low Mach number axial fan and scattered by an obstacle. The model proposed is a semi-analytical solution to predict the acoustic field of an industrial fan including installation effects. The model is based on Amiet's theory on the turbulenceinterac...
Conference Paper
Full-text available
Curle’s analogy has proved to be well suited for simulating noise radiated by low Mach flows interacting with steady bodies. It only requires surface pressure and leads to accurate results when the turbulence/body interaction region is acoustically compact. If compactness is not satisfied, it becomes delicate to use when an incompressible flow mode...
Conference Paper
Acoustic performance of vehicle engines is a real challenge for powertrain design engineers. Quiet engines are required to reduce noise pollution and satisfy pass-by noise regulations, but also to improve the driving comfort. Simulation techniques such as the Boundary Element Method (BEM) have already been available for some time and allow predicti...
Conference Paper
Full-text available
For the virtual design optimization of mechanical structures, a wide range of vibro-acoustic prediction tools are nowadays available. Ideally, these tools should be applicable in the full audible frequency range from 20Hz up to 20kHz. However in practice, specific methods are applicable only in a limited frequency region. Finite Element (FEM) and B...
Conference Paper
Full-text available
An energy flow post-processing tool for structural dynamic analysis is presented based on a conventional finite element (FE) analysis. The global dynamic behaviour of a system and local subcomponent descriptions can provide efficient energy distribution evaluation and vibro-acoustic analysis of complex structures. The use of energy as a response va...
Article
Inverse numerical acoustics is a method which reconstructs the source surface normal velocity from the sound measured in the near-field around the source. This is of particular interest when the source is rotating or moving, too light or too hot to be instrumented by accelerometers. The use of laser vibrometers is often of no remedy due to the comp...
Conference Paper
Inverse numerical acoustics is a method which reconstructs the source surface normal velocity from the sound measured in the near-field around the source. This is of particular interest when the source is rotating or moving, too light or too hot to be instrumented by accelerometers. The use of laser vibrometers is often of no remedy due to the comp...
Conference Paper
This paper deals with Amiet's theory for incoming turbulence noise in three different aspects. In the first part, the effects of geometric and acoustic near-field terms are examined using numerical integration methods. A semi-analytical formulation, which takes an intermediate level of geometrical near-field correction into account, is proposed. Se...
Article
An Inverse Numerical Acoustics (INA) methodology is presented, which can be used to reconstruct the source surface normal velocity radiated by mechanical structures from the sound measured in the near-field around the source. This is of particular interest when the source is rotating or moving, or too light or too hot to be instrumented by accelero...
Conference Paper
Full-text available
This paper discusses two recent advances in finite element methods for Helmholtz equation. To reduce the pollution effect arising in the discretization of short wavelengths, a Generalized Galerkin least squares formulation is employed. This approach proves to outperform standard Galerkin formulation on realistic configurations and allows to relax s...
Conference Paper
Full-text available
One major bottleneck of the Galerkin FE approach for solving Helmholtz equation is the so-called pollution effect. For large scale problems, when the dimensions of the domain become significant when compared to the wavelength, the well known " rule of thumb " which consists in using 8 to 10 points per wavelength, can yield notable errors. In practi...
Conference Paper
Full-text available
This paper deals with a new implementation of the perfectly matched layers (PML) for Helmholtz equation. Our approach is based on the “locally-conformal” technique introduced for Maxwell equations by Ozgun et al. This method greatly extends the flexibility of the classical Cartesian, cylindrical or spherical based layer definition, allowing to cope...
Article
The application of near-field acoustic holography to a loudspeaker source is investigated. The source consisted of an arrangement of eight loudspeakers on one side of a rectangular wooden enclosure. An accompanying paper presents the results for pure tonal sources driving the loudspeakers. In this paper, a sum of harmonic waves of differing frequen...
Article
This paper investigates the application of near-field acoustic holography and intensity techniques to a loudspeaker source. The source consisted of an arrangement of eight loudspeakers on one side of a rectangular wooden enclosure. Sinusoidal waves of a specific frequency, amplitude and phase were used to drive the loudspeakers. Sound Power levels...
Conference Paper
Full-text available
Boundary element method is well known and extensively used to solve acoustic radiation problems. It is especially appropriated for exterior radiation since the fluid domain does not need to be meshed, as opposed to the finite element method. However, the mathematical formulation leads to a dense matrix system of equations. Therefore, the size of th...
Article
Boundary element method is well known and extensively used to solve acoustic radiation problems. It is especially appropriated for exterior radiation since the fluid domain does not need to be meshed, as opposed to the finite element method. However, the mathematical formulation leads to a dense matrix system of equations. Therefore, the size of th...
Conference Paper
The aeroacoustical analogy derived by Curle for the prediction of the sound resulting from turbulence/body interaction has been proved quite powerful for low Helmholtz numbers, i.e. when the interaction region is acoustically compact. In such case, incompressible flow modeling is appropriate to obtain the source field used as input of the analogy....
Article
Finite elements have been successfully used over the past decade to predict the vibro-acoustic behavior of complex large systems as encountered in the transportation industry. Nevertheless, some challenges are still not completely solved as for instance the modeling of multilayer porous materials used to reduce the noise in cavities. A simple model...
Article
Wind induced sound and vibrations are areas where a lot of research efforts are spent today. Due to the random nature of turbulent flow fields, a deterministic approach to the problem will just describe one of many possible solutions. To reduce statistical uncertainty and achieve a robust solution of a problem a large number of calculations can be...
Article
Computational Fluid Dynamic (CFD) studies of sunroof buffeting on production vehicles demonstrate accurate prediction of the main buffeting frequency and its harmonics. For production vehicles, none to date has illustrated the phenomenon of buffeting intensity maximization over a vehicle speed range, at a frequency related to the volume of the pass...
Article
Source identification applied to a truck engine and using inverse numerical acoustics is presented. The approach is based on acoustic transfer vectors (ATV) and truncated singular value decomposition (SVD). Acoustic transfer vectors are arrays of transfer functions between surface normal velocity and acoustic pressure at response points. They can b...
Article
SUMMARY This paper investigates the tonal noise radiated by a subsonic blower fan of an HVAC system. Numerical simulations have been performed and compared to measurements. The numerical simulation is based on the aero-acoustic analogy where the unsteady flow is first computed using STAR-CD and then passed to LMS SYSNOISE to compute the acoustic ra...
Article
Reducing time-to-market, reducing development and production costs and increasing acoustic comfort, means less physical prototyping and more predictive modeling. However, predictive acoustic and vibro-acoustic models using FEM and BEM methods have often had limited usefulness, partly due to the long times taken to get the substantial amounts of res...
Article
This article presents the numerical modeling of noise radiated by an engine, using the so-called Acoustic Transfer Vectors and Modal Acoustic Transfer Vectors concept. Acoustic Transfer Vectors are input-output relations between the normal structural velocity of the radiating surface and the sound pressure level at a specific field point and can th...
Article
During the past three decades the component mode synthesis methods were extensively presented in the literature. Unfortunately, it seems that no convergence criterion was clearly defined in the literature. A free interface method is presented in this paper and six test cases are used to evaluate the number of retained substructure modes necessary t...
Article
Full-text available
Nearfield Acoustic Holography has proven to be a powerful tool for source identification. Nevertheless, the approach is limited to simple sources and measurement surfaces. To overcome this limitation, inverse boundary element methods are often used. A new approach based on the acoustic transfer vectors and truncated singular value decomposition is...
Article
The analysis of the coupled vibroacoustic behavior of a structure-cavity system is often performed using the in vacuo structure modes and the rigid cavity modes. Unfortunately, the use of such a modal basis can result in a poor convergence when the high-frequency modes of one of the two subsystems are coupled to the low-frequency modes of the other...
Article
The variational boundary element method (VBEM) is widely used to compute the acoustic radiation of structures. The classical numerical implementation of the VBEM suffers from the computational cost associated with double surface integration. In a previous paper [1], the authors proposed a novel method, based on multipole expansions, to accelerate t...
Article
We study the vibroacoustic response of a rectangular box. A free interface component mode synthesis is used for the modal analysis of the box. The structure modes are then coupled to the cavity modes using a modal superposition technique. For the radiation of the box, an indirect variational formulation is developed in terms of surface integral equ...
Article
The acoustic radiation of general structures with Neumann's boundary condition using Variational Boundary Element Method (VBEM) is considered. The classical numerical implementation of the VBEM suffers from the computation cost associated with double surface integration. To alleviate this limitation, a novel acceleration method is proposed. The met...
Article
State-of-the-art methods for the study of the vibroacoustic response of a rectangular box are presented. Fast and accurate approaches are used for structural modeling, cavity coupling, and acoustic radiation modeling. A free interface component mode synthesis is used for the modal analysis of the box. The structural modes are then coupled to the ca...
Article
The calculation of the acoustic and vibration response of an elastic cavity is considered. The presented technique uses a modd decomposition for the structure in vacuo and the cavity to re-write the coupled equations and account for the impedance condition at the treated elastic wds, internal acoustic sources and mechanical excitations in terms of...
Article
This paper discusses the prediction of transmission loss through multilayer structures with porous materials. First, a brief review of recent formulations for multilayer structures with poroelastic materials is presented. Second, the transmission loss problem is described and formulated using a coupled finite element and boundary element procedure....
Article
In this paper, the variational boundary element method (VBEM) is used to compute the acoustic radiation of structures with Neumann's boundary condition. The classical numerical implementation of the VBEM suffers from the computation cost associated with double surface integration. A novel method, based on multipole expansions, is proposed to allevi...
Article
The acoustic radiation of general structures with Neumann’s boundary condition using the variational boundary element method (VBEM) is considered. The classical numerical implementation of the VBEM suffers from the computation cost associated with double surface integrals. To circumvent this limitation a novel acceleration method is proposed. It is...
Article
The noise generated during the passage of vehicles on open grid bridge decks has a strong tonal component, which can be a source of annoyance to nearby residents. Potential sources of noise are the vibrations of the grid and the vibrations of the tire. In this paper, the relative contributions from the grid and the tire are investigated by using an...
Article
The paper presents Acoustic Transfer Vectors (ATVs) and Modal Acoustic Transfer Vectors (MATVs) and their use in acoustic radiation prediction, particularly from the surfaces of engines and their components and from other rotating machinery. Acoustic Transfer Vectors are input-output relations between the normal structural velocity of the radiating...
Article
Engineering an automobile has an ever-increasing challenge: to satisfy many competing objectives for the attributes of the full vehicle. The vehicle development process is under continuous pressure to reduce development time, reduce product cost, and come up with innovative designs by exploring more options. At the same time, customer demands and p...
Article
Full-text available
The Finite Element Method (FEM) and Boundary Element Method (BEM) are commonly used as numerical prediction techniques for vibro-acoustic analysis and design. Due to the large model sizes and subsequent computational loads, the practical use of these techniques is restricted to low- frequency applications. However, there is a strong industrial need...
Article
Flow-induced noise is becoming a major performance and quality issue that industries are facing in different sectors: automotive, aerospace, process equipment and others. This paper presents the implementation of a procedure for deriving and analyzing aero-acoustics, using an Acoustic Analogy approach. The method links the leading commercial CFD co...
Article
Full-text available
Noise radiation from rotating or reciprocating machinery such as automotive engines and electric motors can be predicted accurately with boundary element models, linked to structural finite element models, but the calculation times are often too long if results are wanted at multiple frequencies and multiple rotational speeds or loads. Truly useful...

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