Magnetic resonance imaging of sonicated fluids

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When a high-intensity sound is applied to a fluid, many interesting things happen. For example, the fluid begins to flow away from the sound source, which is called "acoustic streaming". If the sound is strong enough, the liquid looks like it is boiling, complete with hissing sounds and bubbles. This is called "cavitation", the growth, oscillation and collapse of bubbles in liquid. Very fast collapse of cavitating bubble creates very extreme conditions of matter inside the bubble, similar to those on the surface of the Sun, with temperatures above 5000K and emission of light (sonoluminescence). Information on cavitation bubble dynamics is crucial for a better understanding and control of sound-induced phenomena. Strong sound mixes fluids and enhances their propagation in porous media, which is important for oil recovery and ground remediation. Ultrasound-induced chemical reactions and extreme conditions inside cavitating bubbles will lead to new chemical products and novel materials.   In my Discovery grant application, I propose new methods of measurement and control of the effects of ultrasound, using strong magnetic fields. The proposed research has two principal components. (1) Magnetic Resonance Imaging characterization of physical effects of ultrasound such as cavitation and emulsification, and how these effects modify propagation of fluids in porous media. The second component, (2) will be the development of methods of to control single bubble levitation and sonoluminescence. For single bubble sonoluminescence, the bubble collapse is never symmetric if the experiment is performed on Earth: buoyancy will alter the bubble dynamics. There are two ways to correct for this effect: perform the experiment in space (such an experiment is scheduled by NASA for the International Space Station this year) or find a force that will compensate gravity. We will employ very strong magnetic field gradients for this compensation.