ИСТИНА

Numerical experiments on N-waves propagation through a turbulent layer were performed based on the 2D parabolic KZK-type equation. Acoustic pulse wavelength and spatial scales of the turbulence with a modified von Karman spectrum corresponded to laboratory scale experiments performed earlier at Ecole Centrale de Lyon. Similar waveform distortions were observed in numerical and laboratory experiments. Statistics of peak overpressure and shock front steepness were analyzed for linear and nonlinear propagation cases. Statistical data included cumulative probabilities to observe waveforms with increased amplitude and shock front steepness in comparison to nominal levels. In the case of linear propagation, strong caustics with high pressure level were formed at some propagation distance, but no increase of shock front steepness was observed. A propagation distance scaling law for statistical data curves was proposed to account for dependence of the distance for strong caustics formation on the turbulence intensity. Simulations with nonlinear effects demonstrated that nonlinear steepening for N-waves with initial amplitudes of 50-100 Pa was sufficient to counteract the smearing effect introduced by the turbulence. Work was supported by RSF-17-72-10277 and by the Labex CeLyA of Universite de Lyon, operated by the French National Research Agency (ANR-10-LABX-0060/ ANR-11-IDEX-0007).