Nonlinear effects in infrasound propagation simulations

International audienceIn the framework of the Comprehensive Nuclear-Test-Ban Treaty, long range propagation of infrasound through the atmosphere is investigated using numerical models. The study problem is a cylindrical blast in an inhomogeneous atmosphere. Vertical profiles of temperature, wind and density obtained during the Misty Picture High explosive experiment conducted in May 1987 are used. The propagation is modeled using two codes. First, the full 2-D Navier-Stokes equations are solved with a low-dispersion and low-dissipation finite-difference algorithm initially developed for aeroacoustics. Second, a nonlinear ray tracing model based on weak shock and locally plane wave assumptions is used. In this code, the waveform evolves along rays following Burgers' equation. The initialisation of the cylindrical blast wave is described for both codes. A benchmark case of propagation is defined and numerical comparisons are performed. Absorption and nonlinear effects are investigated in detail for both stratospheric and thermospheric paths. Some limits of the ray tracing model are shown and quantified