### ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

## 3aPAa4. A numerical study of random focusing for plane waves propagating
in scalar or vectorial turbulent media.

**Philippe Blanc-Benon
**

**
Daniel Juve
**

**
**
*Lab. de Mecan. des Fluides et d'Acoust., URA-CNRS 263, BP 163, Ecole
Centrale de Lyon, 69131 Ecully Cedex, France
*

*
*
A numerical simulation has been developed to investigate the random
focusing for an acoustic plane wave propagating through scalar or vectorial
turbulent fields. The turbulence is represented as a set of realizations of
random fields (temperature or incompressible velocity) generated by a limited
number of random Fourier modes [M. J. Karweit et al., J. Acoust. Soc. Am. 89,
52--62 (1991)]. Through each realization the propagation of a plane wave is
considered in either the geometric or the parabolic approximation. Using the
ray equations the ray trajectories and the location of the instantaneous
caustics are computed. The acoustic pressure field and the intensity
fluctuations are obtained by solving a wide-angle parabolic equation. Ensemble
averaging is then performed to evaluate the probability distribution of the
occurrence of caustics and the variance of acoustic intensity fluctuations. For
2-D and 3-D scalar simulations the results demonstrate that the position of
caustics as well as the maximum peak in the scintillation index are governed by
universal parameters related to the transverse spatial derivatives of the
correlation function of the fluctuating components of the turbulent medium.
Results will be given to generalize the definition of these universal
parameters for sound propagation in random velocity fields.