Influence of thermal overlap effects on the ultrasonic attenuation spectraof polydisperse oil-in-water emulsions

This study examines the influence of thermal overlap effects on the ultraso nic attenuation of polydisperse emulsions. The ultrasonic attenuation coeff icient of a series of corn oil-in-water emulsions was measured as a functio n of droplet concentration (1-50 wt %), volume-surface mean droplet radius (r(32) = 0-12 and 0.58 mu m), and frequency (1-120 MHz). There was good agr eement between these measurements and predictions of the traditional ultras onic scattering theory (UST) for the emulsions containing 0.58 mu m droplet s, but the UST greatly overestimated the attenuation of the emulsions conta ining 0.12 mu m droplets, especially at higher droplet concentrations, due to thermal overlap effects. We show that the UST can be extended to account for these effects using a core-shell model and highlight the range of expe rimental conditions over which the existing UST can be successfully used.