Experimental Investigation of the Travel-time Variance of an Acoustic Wave Propagating Through The Grid-generated TurbulenceJournal of Waves in Random and Complex Media
AbstractAn experimental technique for the investigation of the behaviour of acoustic wave propagation through a turbulent medium is discussed. The present study utilizes the ultrasonic travel-time technique to diagnose a grid-generated turbulence. Travel-time variance is studied versus mean flow velocity, travel distance and outer turbulence scale. The effect of thermal fluctuations, which result in fluctuations of sound speed, is studied using a heated-grid experiment. Experimental data obtained using ultrasonic technique confirm numerical and theoretical predictions of nonlinear increase of the travel-time variance with propagation distance, which could be connected to the occurrence of caustics. The effect of turbulent intensity on the travel-time variance and appearance of caustics is studied. It is demonstrated experimentally that the higher turbulence intensity leads to the shorter distance, at which the first caustic occurs. The probability density for caustics appearance is analyzed against the measured wave amplitude fluctuations. The analysis reveals that the region of high-amplitude fluctuations corresponds to the region where the probability of formation of random caustics differs from zero. Experimental results are in very good agreement with theoretical and numerical predictions.
Citation InformationTatiana A. Andreeva and William W. Durgin. "Experimental Investigation of the Travel-time Variance of an Acoustic Wave Propagating Through The Grid-generated Turbulence" Journal of Waves in Random and Complex Media Vol. 15 Iss. 3 (2005) p. 365 - 374
Available at: http://works.bepress.com/wdurgin/42/