Paper Number
NF19
Session
Non-Newtonian Fluid Mechanics & Flow Instabilities
Title
Acoustically enhanced bubble removal from yield-stress fluids
Presentation Date and Time
October 17, 2018 (Wednesday) 1:30
Track / Room
Track 7 / Plaza II
Authors
- De Corato, Marco (Imperial College London, Chemical Engineering)
- Saint-Michel, Brice (Imperial College, Department of Chemical Engineering)
- Garbin, Valeria (Imperial College London, Department of Chemical Engineering)
Author and Affiliation Lines
Marco De Corato, Brice Saint-Michel, and Valeria Garbin
Department of Chemical Engineering, Imperial College London, London SW72AZ, United Kingdom
Speaker / Presenter
De Corato, Marco
Text of Abstract
Yield-stress fluids are encountered in many industrial areas such as formulated products, oil recovery, and wastewater treatment. In these applications, small gas bubbles are often generated or trapped while processing the fluid. Once suspended in a yield-stress fluid, micron-sized bubbles are difficult to remove because their buoyancy force is below the yield stress. The presence of trapped bubbles may affect the product quality or process performance, hence methods for removal of bubbles from yield-stress fluids are desirable. We explore the use of ultrasound to release micron-sized bubbles from yield-stress fluids. Preliminary experiments performed in our lab suggest that micron-sized bubble can become free to escape after less than a minute of exposure to ultrasound. We hypothesize that the radial oscillations of the bubbles in the ultrasound field cause local yielding. We develop a theoretical framework to describe the deformation of yield-stress fluids by oscillating microbubbles. We modify the Rayleigh-Plesset equation governing the radial dynamics of the bubble to take into account the complex behaviour of the fluid. We characterize the amplitude of the radial oscillations of the bubble as a function of the ultrasound frequency, and for different rheological parameters, by solving the Rayleigh-Plesset equation numerically. By quantifying the volume of fluid that is yielded as a function of the amplitude and frequency of the acoustic pressure, it is possible to predict optimal conditions for bubble removal.