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.

Bubbly pipe flow study via refractive index matching

“…The size measurement of such bubbles by the phase-Doppler system re¯ects an average radius of curvature of the scattering portion of the surface of the bubble. This has been argued on theoretical grounds by Durst and Zare (1975) and experimental evidence has been presented by Brena de la Rosa et al (1989) and Tassin and Nikitopoulos (1995). Furthermore, when the bubbles are nonspherical the likelihood of receiving multiple scattering modes increases.…”

“…In the case of bubbles that are transparent, several modes of scattering may result. For most cases of practical interest the most signi®cant modes are re¯ection, ®rst order refraction, and second order refraction (Brena de la Rosa et al, 1989). When the diameter of the incident beams is comparable to the bubble size, all three modes can be received at a given scattering angle (reception angle).…”

Implementation of the Laser Diffraction Technique for Acoustic Cavitation Bubble Investigations

“…The laser diffraction technique deduces the size from the diffraction pattern scattered by the bubble cloud between 0.0988 and 7.7378 (corresponding to the angular field of the 100 mm focal length). By the phase Doppler technique, the diameterphase shift correlation, based on the geometrical optical laws [24], is verified if the receiver unit avoids the diffracted light. In our case, the analysed light component is the refracted light.…”

Statistical description of the bubble cloud resulting from the injection of air into a turbulent water jet

“…1) in the forward scatter direction. This gives a linear relationship between the phase diflerence and the diameter of the scattering bubble, as calculated from analytical modeling using the Lorenz-Mie theory (Bachalo and Houser, 1984;Breña de la Rosa et al, 1989, 1990Sankar and Bachalo, 1991). In all the cases presented here the measurements were taken at 20 nozzle diameters, 10 diameters downstream from the air injection point.…”