Ultrasonic measurement of bubble cloud size profiles

Abstract

The detection and sizing of microbubbles have applications in many fields. A technique of insonifying bubbles simultaneously with a ‘‘pumping field’’ which is swept through their resonance frequencies, together with a higher frequency ‘‘imaging field’’ having spatial resolution, is shown to be capable of ultrasonically estimating the size distribution of microbubbles in fluids noninvasively and in real time. Experimental results are presented which show good agreement between the size profile of bubbles measured optically, and that determined from this double frequency method. The method is also shown to detect bubbles below the limit of optical observation.