Abstract: Theoretical and experimental analysis of the scattering of ultrasonic pulses at the turbulent air flow boundary is carried out. For theoretical estimates, the solution of plane wave’s reflection from a randomly inhomogeneous medium by using invariant immersion method is used. It is shown, that not only the amplitude and the phase of the signal depend on the scales and in the intensity of random fluctuations of sound speed, but also the spatio-temporal scales of the pulse and its time delay. Experimental studies were carried out according to a multi-ray scheme, when the received signal is a superposition of pulses that came along different trajectories. Digital phase modulation and correlation signal processing are used to estimate small time delays. It is shown, that waveguide propagation of ultrasound with a significant change in the ultrasound signal delay is realized in the turbulent layer at the boundary of the fan’s air flow due to the localization effect.
Index terms: ultrasound, turbulent flow, pulse measurements, localization effect, phase-modulated signals, correlation processing.


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