Sensitivity of sonic boom propagation throughout a turbulent atmosphere

Sensitivity of sonic boom propagation throughout a turbulent atmosphere is investigated. Three types of boom of same amplitude but different initial shapes: an ideal N-wave, a measured boom (NASA data for F-18) and a “low” boom (C25D mock-up) with increased rise time are studied. The atmosphere is supposed to be a quiescent and isothermal medium with a superposed synthetic velocity field with homogeneous and isotropic statistical properties satisfying a von Kármán energy spectrum. Using the “random field generation method,” the flow velocity turbulent field is governed by three independent parameters: a random matrix, an intensity parameter and a scale parameter (turbulence integral scale). The flow velocity is then used as a base flow for a in-house software called FLHOWARD designed to compute the propagation of acoustic shock waves in heterogeneous media. In order to reduce the number of simulations compared to a Monte-Carlo approach, the study is performed within the generalized chaos polynomial (gPC) framework. Various convergence tests have been performed to define the optimal discretization and gPC order. Stochastic evolution of selected metrics along a 1 km distance are investigated.