Development of a high-speed ultrasonic tomography system for measurements of rising bubbles in a horizontal cross-section. (September 2021)

• Record Type: Journal Article
• Authors: Murakawa, Hideki; Shimizu, Tomoyuki; Eckert, Sven
• Is Part Of: Measurement. Volume 182(2021)
• Publication Date: 2021-09
• Subjects: Full-matrix capture -- Reflection mode -- Time-series filtering -- Pseudo three-dimensional image -- Bubble column -- Large divergence-angle transducer; Weights and measures -- Periodicals; Measurement -- Periodicals; Measurement; Weights and measures; Periodicals; 530.8
• DOI: 10.1016/j.measurement.2021.109654
• Languages: English
• ISSNs: 0263-2241

Abstract

Highlights: A 110° divergence angle and constant sound field thickness transducer was developed. 1 ms time resolution and 1000 frames/s frame rate tomography was developed. A time-series filtering method was proposed for use with the tomography data. A sphere moving at 0.70 m/s was successfully measured at 500 frames/s. The system is capable for qualitative observation of bubble motion. Abstract: The present study deals with high-speed ultrasonic tomography (UT) as a powerful tool to characterize the behavior of multiphase flows. A major goal of the work is to improve the temporal resolution for the detection of transit flow structures and time-dependent phenomena such as the incidence of rising gas bubbles. A special transducer with a wide divergence angle of 110° and a vertical height of the measurement volume of approx. 4 mm was developed and tested. The system thus enables the acquisition of cross-sectional images at a frame rate of up to 1000 frames/s. Scatter noise was eliminated using a time series filtering method. This UT system was applied to a chain of gas bubbles rising in a cylindrical container with an internal diameter of 50 mm. The measurement system provides qualitative observations of the turbulent dynamics of bubbly flows including bubble-bubble interactions, such as the coalescence of individual bubbles.