A detailed experimental study of spatial characteristics for laser beams propagating through the turbulent aerojet has been performed. The obtained results for radiation wavelengths of 0.53, 1.06, and 10.6 microm were used for the development of the numerical mathematical model for beam propagation through an extreme turbulent medium. The combination of parameters and algorithms for the numerical model was determined, which made it possible to obtain computational laser beam spatial characteristics that agreed quite well with the experimental data. Good agreement between the results points to the possibility, in principle, to regard the central jet area as a medium locally homogeneous in the statistical sense and anisotropic on the turbulent outer scales.

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One-, half-and ten-micron wavelength radiation was used to study laser beam propagation through turbojet aircraft engine exhaust. A feature of the method was that "instantaneous" distributions of the beam intensity were recorded during the experiment. Analysis of experimental data has shown that turbulent stream has a dramatic impact on spatial characteristics of a laser beam. For example, the averaged angle divergence for 30-mm one-micron beam becomes about ten times higher than its diffraction divergence. Results of different experiments showed that the average angle divergence of the narrow onemicron beam disturbed by the jet plume is several times less than that of the ten-micron beam which is characterized by a large diffraction divergence, and that of the half-micron beam stronger subjected to disturbances. Experiments in which the beam crossed the plume close to a nozzle at p = 90°, 45° and 1 0° have shown that angular divergence increases with decreasing cross-angle, practically doubling the value when coming from the maximal angle of q =90°to the minimal p = 10°. Mathematical models have been derived, based on the experimental studies. The value of the structural characteristic in a turbulent stream is in the range of Cn2 i0 m213.

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