In-situ measurements of void fractions and bubble size distributions in bubble curtains

TL;DR

This paper introduces a new in-situ measurement system combining electrical and optical sensors to accurately analyze bubble properties in bubble curtains, revealing differences in plume behavior based on hose type.

Contribution

A novel measurement system for in-situ bubble analysis in bubble curtains, validated against optical methods, and applied to compare different hose types.

Findings

Good agreement between electrical and optical measurements.

Self-similar behavior observed in bubble plumes.

Porous hoses produce higher spreading rates.

Abstract

We report the development of a novel measurement system designed to measure bubble properties in bubble curtains (i.e. planar bubble plumes) in-situ alongside acoustical measurements. Our approach is based on electrical, contact-based needle sensors in combination with an optical system. The latter is used for calibration and validation purposes. Correcting for the insensitive distance of the needle tips yields very good agreement between the two approaches in terms of the local void fraction and bubble size distributions. Finally, the system is employed to study bubble plumes evolving from three different hose types. All hoses display consistent self-similar behaviour with spreading rates increasing with increasing gas flow. The spreading is further found to be significantly higher when the bubble plumes originated from a porous hose compared to the two other hose types featuring either discrete holes or nozzle elements.