title: Laboratory-scale experiment to study nonlinear N-wave distortion by thermal turbulence.
abstract: The nonlinear propagation of spark-generated N-waves through thermal turbulence is experimentally studied at the laboratory scale under well-controlled conditions. A grid of electrical resistors was used to generate the turbulent field, well described by a modified von Kármán model. A spark source was used to generate high-amplitude (~1500 Pa) and short duration (~50 μs) N-waves. Thousands of waveforms were acquired at distances from 250 to 1750 mm from the source (~15 to 100 wavelengths). The mean values and the probability densities of the peak pressure, the deviation angle, and the rise time of the pressure wave were obtained as functions of propagation distance through turbulence. The peak pressure distributions were described using a generalized gamma distribution, whose coefficients depend on the propagation distance. A line array of microphones was used to analyze the effect of turbulence on the propagation direction. The angle of deviation induced by turbulence was found to be smaller than 15°, which validates the use of the parabolic equation method to model this kind of experiment. The transverse size of the focus regions was estimated to be on the order of the acoustic wavelength for propagation distances longer than 50 wavelengths.
authors.affiliation: Laboratoire de Mécanique des Fluides et d'Acoustique, UMR CNRS 5509, École Centrale de Lyon, Université de Lyon, 36, avenue Guy de Collongue, 69134 Écully Cedex, France.
authors.forename: Édouard
authors.initials: É
authors.lastname: Salze
authors.affiliation: Department of General Physics and Magneto-Ordered Matter, Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow 119991, Russia.
authors.forename: Petr
authors.initials: P
authors.lastname: Yuldashev
authors.affiliation: Laboratoire de Mécanique des Fluides et d'Acoustique, UMR CNRS 5509, Université Lyon 1, Université de Lyon, 43 boulevard du 11 novembre 1918, 69622 Villeurbanne Cedex, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Ollivier
authors.affiliation: Department of Acoustics, Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow 119991, Russia.
authors.forename: Vera
authors.initials: V
authors.lastname: Khokhlova
authors.affiliation: Laboratoire de Mécanique des Fluides et d'Acoustique, UMR CNRS 5509, École Centrale de Lyon, Université de Lyon, 36, avenue Guy de Collongue, 69134 Écully Cedex, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Blanc-Benon