Reflection of sonic boom over realistic urban areas

Abstract

This study aims at analyzing sonic boom reflection over realistic urban areas. For this purpose, numerical simulations are performed. The 2D Euler equations are solved using high-order finite-difference methods, following Emmanuelli et al. [J. Acoust. Soc. Am. 149, 2437–2450 (2021)]. The local climate zone classification of urban morphologies [Steward and Oke, Bull. Am. Meteorol. Soc. 93, 1879–1900 (2012)] is used to generate ten typical geometries. Two booms, an N-wave and a low-boom wave, are considered. The pressure waveforms along the profiles are analyzed first. In addition to the geometric arrivals, low-frequency oscillations, associated with resonance modes of the street canyons, are noted. They induce an important increase in the duration of the signals. Their frequency and amplitude depend on the street width and on the boom wave. The noise levels are then investigated. Depending on the urban geometry, two behaviors are highlighted. For a sparse arrangement of buildings, the evolution of the levels is similar than for isolated buildings, with an amplification on the front facade and a reduction on the rear facade. For a dense arrangement, it is more complex due to the multiple reflections on the buildings. Finally, the levels follow a comparable evolution for both boom waves.