Hélène Bailliet

Université de Poitiers | UP · Institut de recherche de Poitiers : Recherche ingénierie en matériaux, mécanique et énergétique pour les transports, l'énergie et l'environnement (Institut Pprime)

This study focuses on the influences of natural convection on the temperature distribution in a compact thermoacoustic coaxial heat pump. The behaviour of this device is quite consistent with results of Rott's linear theory of thermoacoustics, but early measurements reveal a non-uniformity of the temperature along the transverse dimension of the co...

Increasing the capacity of thermoacoustic machines (engines or refrigerators) requires increasing the diameter of the regenerator, which may result in non-uniform temperature distributions inside the regenerator. In the current study, the temperature is measured at different radial and axial locations inside the regenerator of a thermoacoustic refr...

Reflection of propagating modes is studied at the exit of a cylindrical acoustic wave guide from both an experimental and a numerical point of view. The plane mode and several purely azimuthal higher modes are extracted by means of modal decomposition and the uncoupled reflection coefficients of each mode are obtained using two microphonic antennas...

Increasing the capacity of thermoacoustic machines (engines or refrigerators) requires increasing the diameter of the regenerator, which may result in non-uniform temperature distributions inside the regenerator. In the current study, the temperature is measured at different radial and axial locations inside the regenerator of a thermoacoustic refr...

The current study reports an experimental investigation of flow regimes for acoustically oscillating flows in the near-wall region of a resonator. Particle Image Velocimetry (PIV) is used to measure axial and transverse velocity components inside an empty square resonator over the acoustic cycle for a wide range of Reynolds numbers and at a high Wo...

Complex coupling between thermal effects and Rayleigh streaming in a standing wave guide at high acoustic levels is analyzed numerically. The approach is guided by the recent analytical study, showing that reverse streaming cells can form if the nonlinear Reynolds number exceeds a value depending on the wave frequency and thermophysical properties...

The present study focuses on acoustically induced thermal effects on Rayleigh streaming inside a resonator. Firstly, we consider the effect of the transverse (or wall-normal) mean temperature gradient on the acoustic streaming flow generated by a standing wave between two parallel plates. Analytical expressions for acoustic quantities are developed...

The aim of this study is to investigate the oscillating flow velocity field at the exit of different stacked mesh grid regenerators using Particle Image Velocimetry measurements. Twelve different experimental cases are discussed, yielding oscillating flow fields at the exit of four kinds of regenerators for different acoustic levels. The regenerato...

Thermoacoustic refrigeration technology is a green alternative for the conventional refrigeration system in vehicles. The former uses environmentally friendly inert gases whereas the latter uses chemical refrigerants that can have severe impacts on the environment. In order to apply thermoacoustic technology in the automobile industry, the size and...

This study aims at exploring the potential generation of natural convective flows in thermoacoustic devices. To this effect, two thermoacoustic setups are considered without acoustic oscillations, each setup thus constituting a cavity filled with air and comprising a porous medium heated on one of its ends. In the first configuration, the porous me...

Regenerators (often consisting in stack mesh-wires) and heat exchangers are the core of thermoacoustic devices and, as such, key elements for the efficiency of these systems. In this study, the oscillating flow velocity field at the exit of different regenerators has been measured using Particle Image Velocimetry (PIV) system. Three different mesh...

Acoustic streaming generated by a plane standing wave between two infinite plates or inside a cylindrical tube is considered, under the isentropic flow assumption. A two-dimensional analysis is performed in the linear case of slow streaming motion, based on analytical formal solutions of separate problems, each associated with a specific source ter...

La vélocimétrie par images de particules et l'anémométrie laser Doppler sont utilisées pour étudier le vent acoustique de Rayleigh dans un moteur thermoacoustique. Le vent acoustique est un écoulement stationnaire de second ordre superposé à l’écoulement acoustique oscillant du premier ordre. La mesure de ce type d’écoulement, même dans un résonate...

The influence of both the natural convection and end-effects on Rayleigh streaming pattern in a simple standing-wave thermoacoustic engine is investigated experimentally at different acoustic levels. The axial mean velocity inside the engine is measured using both Laser Doppler Velocimetry and Particle Image Velocimetry. The mean flow patterns are...

Rayleigh streaming is a second order mean flow generated by the interaction between a standing wave and a solid wall. At moderate acoustic levels, the streaming flow is slow, composed of two cells along a quarter wavelength: an inner cell close to the tube wall and an outer cell in the core. When increasing the acoustic level, the streaming flow in...

Thermoacoustic engines suffer from many non-linearities that deteriorate the overall performance. Streaming phenomenon is one of these non-linearities which can affect the performance by convecting a certain amount of heat. In this study, the axial mean velocity distribution inside a basic standing-wave thermoacoustic engine is measured using Laser...

The effect of inertia on Rayleigh streaming generated inside a cylindrical resonator where a mono-frequency standing wave is imposed, is investigated numerically and experimentally. To this effect, time evolutions of streaming cells in the near wall region and in the resonator core are analyzed. An analogy with the lid-driven cavity in a cylindrica...

Rayleigh streaming is a mean flow generated by the interaction between a standing wave and a solid wall. In the case of a low amplitude wave inside a cylindrical resonator, the streaming pattern along a quarter wavelength is composed of two toroidal cells: An inner cell close to the tube wall and an outer cell in the core. In the present work the e...

The interaction between an acoustic wave and a solid wall generates a mean steady flow called Rayleigh streaming, generally assumed to be second order in a Mach number expansion. This flow is well known in the case of a stationary plane wave at low amplitude: it has a half-wavelength spatial periodicity and the maximum axial streaming velocity is a...

Rayleigh streaming is a steady flow generated by the interaction between an acoustic wave and a solid wall, generally assumed to be second order in a Mach number expansion. Acoustic streaming is well known in the case of a stationary plane wave at low amplitude: it has a half-wavelength spatial periodicity and the maximum axial streaming velocity i...

Transition to turbulence for an acoustically oscillating flow (without any mean motion) in a resonant wave guide is considered. Departure from the laminar behaviour of the Stokes boundary layer formed in the near wall region is studied both experimentally and numerically for increasing acoustic levels. Laser Doppler Velocimetry is used to measure v...

Since two decades, progresses in Laser velocimetry technics have allowed the latter to become competitive for the investigation of complex acoustic fields. These technics are of particular interest in situations where pressure measurements are not sufficient to entirely describe the acoustic fields, as is the case in nonlinear acoustics. In this pa...

Rayleigh streaming, suspected to hamper the efficiency of thermoacoustic engines, has been the subject of numerous theoretical and experimental studies in the last decades. This phenomenon is well characterized in the case of two-dimensional channels, but streaming in three-dimensional enclosures, such as rectangular channels, is a usually describe...

Measurements of streaming velocity are performed by means of Laser Doppler Velocimetry and Particle Image Velociimetry in an experimental apparatus consisting of a cylindrical waveguide having one loudspeaker at each end for high intensity sound levels. The case of high nonlinear Reynolds number ReNL is particularly investigated. The variation of a...

Rayleigh streaming in a cylindrical acoustic standing waveguide is studied both experimentally and numerically for nonlinear Reynolds numbers from 1 to 30 [ReNL=(U0/c0)(2)(R/δν)(2), with U0 the acoustic velocity amplitude at the velocity antinode, c0 the speed of sound, R the tube radius, and δν the acoustic boundary layer thickness]. Streaming vel...

Spectral estimation of data sequences with randomly missing samples is considered in this paper. A nonparametric missing-data method is proposed based on interpolation followed by a deconvolution procedure. Sample-and-hold interpolation is considered here. The method is based on the analytic expression of the autocorrelation function of the interpo...

Streaming velocity in an acoustic standing waveguide is measured using Laser Dopper Velocimetry (LDV) from low to high acoustic amplitudes. As expected, the axial streaming velocity agrees with the slow streaming theory for low amplitudes but deviates significantly from such predictions for fast streaming. For high amplitudes, an additional outer s...

An asymmetrical constricted rectangular nozzle is designed representing upper incisors in the oral tract. Steady flow through the nozzle is studied for a fixed constriction degree of 70% and bulk Reynolds number Re b =4000. Flow data are obtained numerically by Large Eddy Simulation as well as experimentally from smoke visualisation and from Partic...

An experiment has been set up to study multimodal acoustic propagation inside a cylindrical duct in presence of a turbulent mean flow. This paper describes the preliminary work which has been found necessary for assembling the experiment together with first measurement results. In order to set up this experimental facility, a high level acoustic so...

Flow through the vocal tract is studied through an in vitro rigid replica for different geometrical configurations and steady flow conditions with bulk Reynolds numbers Re<15,000. The vocal tract geometry is approximated by two consecutive obstacles, representing "tongue" and "tooth," in a rectangular channel of fixed length. For the upstream tongu...

Spectral estimation of irregularly sampled velocity data issued from Laser Doppler Anemometry measurements is considered in this paper. A new method is proposed based on linear interpolation followed by a deconvolution procedure. In this method, the analytic expression of the autocorrelation function of the interpolated data is expressed as a linea...

The acoustical behavior and the flow in a rectangular lined channel with grazing flow have been investigated. The liner consists of a ceramic structure of parallel square channels and is locally reacting. In the absence of flow, the liner has a classical behavior: the acoustic transmission coefficient has a minimum at the resonance frequency of the...

At sound levels encountered in musical wind instruments the oscillating flow at the tube termination can produce periodic local non-linear flow effects. PIV is used to measure the complex flow at the termination of a model wind instrument for a range of sound levels and geometries. POD analysis is then applied to the velocity maps, and the ability...

Previous experiments on vocal tract mechanical models for fricatives consonants production –like /s/, /f/,/ch/ for unvoiced ones –has shown the importance of the geometrical configuration on the complex aeroacoustical noise signal produced [3]: the shape of the constriction, the shape and area function of the vocal tract downstream of the constrict...

Production of fricatives consonants is a complex aeroacoustical problem involving the interaction of turbulent airflow with the particular geometry of the vocal tract. The current study introduces a simplified mechanical static vocal tract including a tongue replica and a rectangular thin obstacle downstream of the constriction formed by the tongue...

The adaptation of Laser Doppler Velocimetry (LDV) and Particle Image Velocimetry (PIV) for acoustic boundary layer measurements is considered. The specificities of acoustic boundary layer are presented and the theoretical expression of acoustic particle velocity is reminded. Appropriate parameters of the PIV system for sound measurements are determ...

A statistical model of the Laser Doppler signal in the case of pure acoustics is proposed. It appears that two different cases should be considered depending on the ratio of acoustic displacement amplitude to probe volume diameter. The processing of Laser Doppler Velocimetry signal in the case of high particle displacements (with oscillations acros...

A preliminary study was conducted to observe the influence of a stack on the Rayleigh streaming pattern for application to thermoacoustic devices. The velocity field was estimated from laser Doppler velocimetry measurements in a resonator first without a stack; then a stack was placed at various positions along the resonator axis for various acoust...

Lined ducts are widely used to reduce noise radiation from ducts, from air conditioning systems to turbofan engines. Liners may sustain some instabilities although there is no definite knowledge on that subject. Some analytical studies based on simple flow models have predicted the existence of unstable hydrodynamic modes, but their prediction capa...

Thermoacoustic engines and refrigerators with practical levels of heating or pumping power must generally operate at high pressure amplitudes. When used to describe the behavior of such high-amplitude thermoacoustic devices, the well-established foundations of thermoacoustics, based on the acoustic approximation, reach their limits. It is necessary...

Acoustic streaming has harmful consequences on thermoacoustic machines behaviour because of the associated heat transfers. A preliminary study was carried out in order to study the effect of an obstacle on the Rayleigh cells to help in understanding the role of such phenomena in thermoacoustic machines. An obstacle was introduced in a half-waveleng...

Sound production due to turbulence is widely shown to be an important phenomenon involved in a.o. fricatives, singing, whispering and speech pathologies. In spite of it relevance, only a few recent models are dealing with turbulence consequences during voiced sound production. The current study presents preliminary results of an experimental charac...

Qualitative and quantitative characterisation of the velocity distribution is an important aspect in order to study respiration related flow phenomena in the upper airways as well as for human speech production. Classical phonation models exploit one-dimensional flow descriptions in order to estimate the pressure forces exerted on the vocal folds t...

An experimental investigation of the acoustic behavior of a liner in a rectangular channel with grazing flow has been conducted. The liner is a locally reacting structure. When increasing the velocity of the grazing flow the transmission coefficient increases at resonance frequency. The transmission coefficient can even become larger than 1 meaning...

Measurements of the axial streaming velocity are performed by means of laser doppler velocimetry in an experimental apparatus consisting of a waveguide having loudspeakers at each end for high intensity sound levels. Streaming is characterized by an appropriate Reynolds number Re(NL), the case Re(NL)<1 corresponding to the so-called slow streaming...

In the vicinity of an abrupt change in cross section, an acoustic wave generates a nonlinear flow. This is investigated experimentally using Particle Image Velocimetry (PIV). The effect of both the acoustic level and the radius of curvature of the abrupt change in section on the flow is studied. At sufficiently high acoustic levels, and past a valu...

Rapport de fin de contrat du projet CoMBE pour la Fondation de Recherche pour l'Aéronautique et l'Espace

HDR, Soutenue le 8 décembre 2008.

In this paper, an analytical solution for the propagation of sound in circular ducts in the presence of Poiseuille mean flow is derived. This solution uses Kummer's functions and it generalizes the results found by Gogate and Munjal. Links between this solution and already-known solutions for more specific cases (no mean flow, uniform flow) are mad...

Laser Doppler velocimetry (LDV) is now recognized as a very useful technique for estimating acoustic velocity with a good time resolution in many applications. Previous research showed that the most important parameter in LDV for acoustics is the particle displacement and particularly its magnitude compared with the size of the probe volume formed...

This communication presents measurements by Particle Image Velocimetry (PIV) of acoustic fields used to estimate the entrance length along the oscillation cycle. The entrance length is defined as the distance from the exit for which the centerline acoustic velocity is significantly perturbed due to end effects. The acoustic wave was driven by a lou...

Non intrusive measurement of a sinusoidal acoustic velocity in a mean movement of fluid is of interest for number of practical application. Although signal processing techniques dedicated to Laser Doppler Velocimetry have been recently developed in order to measure sinusoidal acoustic velocities without flow in a large domain of magnitude and frequ...

Rapport de fin de contrat Sciences et Technologies pour le transport Supersonique (contrat COS)

A derivation of acoustic streaming in a steady-state thermoacoustic device is presented in the case of zero second-order time-averaged mass flux across the resonator section (nonlooped device). This yields analytical expressions for the time-independent second-order velocity, pressure gradient, and time-averaged mass flux in a fluid supporting a te...

It is demonstrated that the temperature oscillations near the edge of the thermoacoustic stack are highly anharmonic even in the case of harmonic acoustic oscillations in the thermoacoustic engines. In the optimum regime for the acoustically induced heat transfer, the amplitude of the second harmonic of the temperature oscillations is comparable to...

The theory of acoustic streaming in an annular thermoacoustic prime-mover is developed. It is predicted that above the threshold for traveling wave excitation the device considered (which does not contain any moving parts or externally imposed pressure gradients) produces circulation of fluid. The heat flux carried by this directional mass flow ins...

The problem of analytical description of temperature fields and heat fluxes in thermoacoustic devices (such as refrigerators and prime-movers) is discussed. It is demonstrated that for the precise analysis of the thermoacoustic process near the edges of the stacks and the heat exchangers, and also for the prediction of the heat fluxes between the s...

The general relation between the velocity of acoustic streaming and the parameters of the acoustic field in a traveling wave (annular) thermoacoustic device is derived. The effects investigated are important for the optimization of thermoacoustic devices because the acoustic streaming contributes to heat transport. © 2000 American Institute of Phys...

It is demonstrated that the temperature oscillations near the edge of the thermoacoustic stack are highly anharmonic even in the case of harmonic acoustic oscillations in the thermoacoustic engines. In the optimum regime for the acoustically induced heat transfer, the amplitude of the second harmonic of the temperature oscillations is comparable to...

Acoustic power flow measurements in the resonator of a thermoacoustic refrigerator are described. The technique of measurement is based on particle velocity measurement by laser Doppler anemometry (L.D.A.) together with microphonic acoustic pressure measurement. The calibration procedure is explained and results of measurements are compared with an...

In thermoacoustic engines, the strong coupling between the sound source and its front and rear loads yields the necessary acoustic energy to be used by fluid particles in the vicinity of the stack for heat transfer from cold to hot thermal sources. An analytical study of this coupling is presented when using available loudspeakers, in order to matc...