Experimental study of acoustic streaming in a high level standing wave guide: Influence of mean temperature and higher harmonics distribution

International audienc

An unexpected balance between outer Rayleigh streaming sources

International audienc

Acoustic viscous boundary layer beyond laminar regime: Particle Image Velocimetry measurements

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 Womersley number. The measurements are compared with LDV measurements in a circular duct. Good agreement between the PIV and LDV measurements is observed. The measured transverse distribution of the axial velocity agrees well with the Stokes boundary layer expectations up to Reynolds number (based on acoustic velocity and viscous boundary layer depth) of 240. At higher Reynolds numbers, the measured velocity distribution deviates from the theoretical expectations, suggesting a change of regime at Reynolds number around 240. To assert the critical Reynolds number, the turbulence intensities and Reynolds stress are estimated. At Reynolds number of 272, an increase in the value of the Reynolds stress is observed at the edge of the viscous penetration depth which is regarded as an indication for changing the flow regime. To better qualify the high amplitude acoustic flow, the spectrum of the turbulent kinetic energy and evolution of the integral length scale over the acoustic cycle are investigated. The decay of turbulent kinetic energy with the wavenumber complies with the universal slope (-5/3). The integral length scale increases during the deceleration stage and decreases at the beginning of the acceleration stage

Numerical and experimental exploration of flow through a teeth-shaped nozzle

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 Particle Image Velocimetry. Quantitative and qualitative exploration of the mean and fluctuating properties of the flow field reveals the impact of the obstacle’s presence on the overall flow field and stresses the need for future in depth studies of the impact of geometrical parameters

Nonparametric spectral analysis of wideband spectrum with missing data via sample-and-hold interpolation and deconvolution

International audienc

Description of the flow through in-vitro models of the glottis during phonation:application to voiced sounds synthesis

In this paper we present results of calculations derived in an earlier paper. These results are illustrated in the form of sound samples. This allows a different and more striking demonstration of the importance of some fluid dynamical features for the purpose of voiced sounds synthesis