Mean flow atmospheric effects and their impact on sonic boom propagation

Abstract

One dimensional augmented Burgers equation has been generally used for nonlinear lossy sonic boom propagation. This equation models the effects of nonlinearities, loss mechanisms such as absorption and dispersion due to molecular relaxation and thermoviscous dissipation, and geometric spreading through ray tube areas including Blokhintzev scaling as well as atmospheric stratification. However, in the presence of atmospheric winds, original terms in the augmented Burgers formulation do not account for the Doppler effects, where the observer is moving with the local flow rather than being fixed in space. Instead, wind is accounted for by updating the ray paths and effective speed of sound. Inclusion of mean flow wind effects in all terms of the augmented Burgers equation allows for an enhanced prediction capability that is closer to the underlying physics. This work will update sBOOM, an augmented Burgers' solver, to reflect the mean flow wind enhancements. The sonic boom ground signatures and other relevant data are compared against those obtained without using mean flow wind effects. The shock rise times, sonic boom duration and peak pressures are some variables that are expected to be different, resulting in differences in noise metrics. Such differences will be discussed and documented for cases which may include shaped low-boom as well as strong shock signatures.