### ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

## 1pPA12. On simulation of sonic-boom propagation with realistic modeling of
the atmospheric turbulence.

**Allan D. Pierce
**

**
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*Dept. of Aerosp. and Mech. Eng., Boston Univ., 110 Cummington St., Boston,
MA 02215
*

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The propagation of sonic booms is from high above the ground to ground
level, and over the path the dominant acoustic length scales in the signatures
fall within what is known as the inertial subrange, for which there is a
considerable body of basic theoretical knowledge. Any model of boom--turbulence
interaction that requires a value for an outer scale has very weak theoretical
basis. However, the range of turbulence scales within the inertial subrange is
huge and different scales have different effects. The present paper argues that
the turbulence can be split in a well-defined and logical manner, with the
resulting scale at which the split occurs serving as an outer scale with
respect to the turbulence that affects the rise times of sonic booms. Although
molecular relaxation accounts for a substantial fraction of the rise times, the
bulk of the thickening during daytime overflights is associated with
turbulence. A theory for such thickening that simultaneously took both
nonlinear steepening and turbulence into account had been proposed in the early
1970s by Plotkin and George, but had been criticized for its dependence on the
choice of an outer scale. The proposed partitioning removes this objection and
combines the salient ideas of Plotkin and George with others proposed by the
author during the same epoch for the effects of inertial-subrange-scale
turbulence on rise times.