F. Coulouvrat

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The influence of the planetary boundary layer on the sonic boom received at the ground level is known since the 1960s to be of major importance. Sonic boom propagation in a turbulent medium is characterized by an increase of the mean rise time and a huge variability. An experiment is conducted at a 1:100,000 scale in water to investigate ultrasonic shock(More)
A model is developed for the propagation of finite amplitude acoustical waves and weak shocks in a straight duct of arbitrary cross section. It generalizes the linear modal solution, assuming mode amplitudes slowly vary along the guide axis under the influence of nonlinearities. Using orthogonality properties, the model finally reduces to a set of ordinary(More)
The present study investigates the focusing of acoustical weak shock waves incoming on a cusped caustic. The theoretical model is based on the Khokhlov-Zabolotskaya equation and its specific boundary conditions. Based on the so-called Guiraud's similitude law for a step shock, a new explanation about the wavefront unfolding due to nonlinear self-refraction(More)
For fluids, the theoretical investigation of shock wave reflection has a good agreement with experiments when the incident shock Mach number is large. But when it is small, theory predicts that Mach reflections are physically unrealistic, which contradicts experimental evidence. This von Neumann paradox is investigated for shear shock waves in soft elastic(More)
Weak shock wave focusing at fold caustics is described by the mixed type elliptic/hyperbolic nonlinear Tricomi equation. This paper presents a new and original numerical method for solving this equation, using a potential formulation and an "exact" numerical solver for handling nonlinearities. Validation tests demonstrate quantitatively the efficiency of(More)
Numerical simulation of nonlinear acoustics and shock waves in a weakly heterogeneous and lossless medium is considered. The wave equation is formulated so as to separate homogeneous diffraction, heterogeneous effects, and nonlinearities. A numerical method called heterogeneous one-way approximation for resolution of diffraction (HOWARD) is developed, that(More)
Time-reversal invariance of nonlinear acoustic wave propagation is experimentally investigated. Reversibility is studied for propagation shorter or longer than shock formation distance. In the first case, time-reversal invariance holds and a sinusoid distorted by nonlinearities during forward propagation progressively recovers its initial shape after the(More)
In the context of growing use of nanoparticles, it is important to be able to characterize all their physical properties in order to understand their behavior, to optimize them, and to control their quality. We showed that ultrasonic spectroscopy provides many of the desired properties. To do so, we used as an example nanocapsules made of a polymer shell(More)
A generalization to the transient regime is developed for waves with a phase singularity of the screw type. These singular waves are commonly called vortices for all kind of waves as, for instance, optical vortex or acoustical vortex. We generalize the definition of vortices to get an azimuthal velocity invariant for all the frequency components contained(More)