Nonlinear interaction of an acoustical wave with a counter-propagating weak shock.

During its propagation, a shock wave may come across and interact with different perturbations, including acoustical waves. While this issue has been the subject of many studies, the particular acoustic-acoustic interaction between a weak shock and a sound wave has been very scarcely investigated. Here, a theory describing the encounter of those two waves is developed, up to second- and third-order.

Acoustic Droplet Vaporization of Perfluorohexane Emulsions Induced by Heterogeneous Nucleation at an Ultrasonic Frequency of 1.1 MHz.

Droplets made of liquid perfluorocarbon undergo a phase transition and transform into microbubbles when triggered by ultrasound of intensity beyond a critical threshold; this mechanism is called acoustic droplet vaporization (ADV). It has been shown that if the intensity of the signal coming from high ultrasonic harmonics are sufficiently high, superharmonic focusing is the mechanism leading to ADV for large droplets (>3 μm) and high frequencies (>1.5 MHz).

Propagation of classical and low booms through kinematic turbulence with uncertain parameters.

The propagation of sonic boom through kinematic turbulence is known to have an important impact on the noise perceived at the ground. In this work, a recent numerical method called FLHOWARD3D based on a one-way approach is used to simulate the propagation of classical and low-boom waveforms. Kinematic turbulence is synthesized following a von Kármán energy spectrum.

Complex eigenrays algorithm for infrasound propagation in a windy range dependent atmosphere.

Ray tracing is a simple and efficient three-dimensional method which reduces the problem of infrasound propagation to a series of one-dimensional cases along acoustical rays. However, in relatively frequent cases, infrasound stations are located in geometrical shadow zones, where only diffracted waves are recorded. The corresponding arrivals cannot be predicted by ray theory.

Numerical observation of secondary Mach stem in weak acoustic shock reflection.

Recently Ram, Geva, and Sadot [J. Fluid Mech. , 219-235 (2015)] showed, experimentally, the formation of a secondary Mach stem generated from the reflection of the primary Mach stem in the aerodynamic regime.