Wave Statistics in Random Media: A Wave-Kinetic Numerical Approach.
Final rept. Sep 85-Jan 87,
VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG
Pagination or Media Count:
The determination of the irradiance distribution of a wave after propagation through a medium of random fluctuations of refractive index at scales large compared to a wavelength has been an intractable problem. It has been possible to calculate moments of the distribution asymptotically or numerically. In this report the author tries to simulate on computer the actual instantaneous random medium, and the propagation of waves through it by means of a phase-space function, the Wigner distribution function which carries information beyond ray crossings and caustics. The method uses an efficient algorithm for propagation of this WDF by discretizing it into Gaussians which are separately propagated. Two canonical problems have been treated by the wave-kinetical method free-space propagation and broadening of a collimated laser beam, and scattering of a plane wave by one Gaussian fluctuation of the refractive index. The results agree with what is expected. Simulation of a strong phase screen has been investigated, but the work is unfinished. The authors random-eddy model is still too unwieldy in size for the extended medium. Quasi-random models are currently being investigated. Keywords Turbulence Diffraction.