Sonic boom reflection over irregular terrain

An overview of recent studies on sonic boom reflection over irregular terrain is presented. Numerical simulations based on the two-dimensional Euler equations are performed using high-order finite-difference time-domain techniques, allowing for an accurate prediction of diffraction. Studies are done for two sonic boom waves: a conventional N-wave and a low-boom wave. First, ground elevation effects on sonic boom are examined. An academic ground profile, corresponding to a terrain depression, is considered to highlight mechanisms at play. In particular, caustics due to ground elevation variations induce another contribution at the ground level, in the form of a U-wave. Results for real ground profiles are then presented and cumulative effects, due to the succession of terrain irregularities, are shown. Second, propagation of sonic boom over an urban profile is investigated. Possible resonance effects inside street canyons are discussed. For all cases, statistics of noise metrics are examined. [This work was performed within the framework of the LabexCeLyA of the University of Lyon, within the program ‘‘Investissements d’Avenir” (ANR-10-LABX-0060/ANR-16-IDEX-0005) operated by the French National Research Agency and has received funding from the European Union's Horizon 2020 research and innovation programme (Grant Agreement No. 769896 (RUMBLE).]