A Theoretical and Experimental Study of the Characterization of Bubbles Using Light Scattering Interferometry

Abstract

The present work details the theoretical and experimental research undertaken to determine the size and morphology of bubbles, and their dynamic characteristics such as velocity, number density, and volume flux using light scattering interferometry. The approach is based on the measurement of the phase difference of the interference fringe pattern which is produced when a particle passing through the probe volume defined by the intersection of two laser beams scatters light and interferes in the surrounding medium. Detailed analytical/numerical modeling of the phase Doppler approach using Mie scattering theory and the geometrical optics approximation resulted in optimum light scattering collection angles and calibration curves for bubble diagnostics. Using several techniques to generate a steady stream of monosize bubbles in the range from 6 μ to 1800 μm in diameter, the measurements obtained using the phase Doppler method were compared with direct photography yielding an agreement of better than 95 percent. The morphology of spheroidal bubbles was also investigated by placing the transmitting and receiving optical units at specified locations with respect to the scatterers. It is believed that this theoretical and experimental work has given the phase Doppler method general validity as applied to bubble diagnostics and promises to become a powerful research tool in the study of two phase flows.