University of Tasmania
Browse

File(s) under permanent embargo

The Influence of Expansion Tube Diameter on Microbubble Production in a Confined Cavitating Jet

conference contribution
posted on 2023-05-23, 15:35 authored by Luka BarbacaLuka Barbaca, Patrick RussellPatrick Russell, Bryce PearceBryce Pearce, Paul BrandnerPaul Brandner
The influence of expansion tube diameter (dₑ) on microbubble production via rapid depressurization of supersaturated water through an orifice and expansion tube is explored in the context of artificial nuclei seeding in hydrodynamic facilities. Microbubble size distribution and production rate are investigated experimentally using high-magnification shadowgraphy. To eliminate the need for a depth-of-field correction, the bubbly plume is discharged into a 0.5 mm thick Hele-Shaw cell. The experiments were performed for a device with fixed orifice diameter, D = 0.25 mm, with the expansion tube diameter in range 0.25 mm ≤ dₑ ≤ 0.75 mm and fixed length of 100 mm. Microbubble production was characterized for a range of generator cavitation numbers (σin j), controlled by varying the device inlet pressure with the outlet open to the atmosphere. Two distinct microbubble populations were generated based on the flow Reynolds (Re) and Weber (We) numbers. For the large dₑ (high Re and We), a polydisperse bubble population with a power law like size distribution is observed, with the bubble production frequency increasing as the diameter approaches the lower resolution limit of the used optical system (≈ 7µm). For the small dₑ (low Re and We), a change in the bubble production regime results with a peak at a value above the lower optical resolution limit, which may be attributed to a decrease in production of sub-Hinze scale products during bubble break-up process. σinj is found to be the main parameter controlling the total production rate, with the measured production frequencies of the order 10³ to 10⁷ Hz. Through variation of the expansion tube geometry, control of the resulting microbubble population is demonstrated, contributing to enhanced capability for modelling of nucleation effects on cavitating flow in hydrodynamic facilities.

Funding

Defence Science and Technology Group

History

Publication title

Proceedings of the 23rd Australasian Fluid Mechanics Conference

Editors

C Lei, B Thornber and S Armfield

Pagination

AFMC2022-272

ISSN

2653-0597

Department/School

Australian Maritime College

Publisher

Australasian Fluid Mechanics Society

Place of publication

Australia

Event title

23rd Australasian Fluid Mechanics Conference - 23AFMC

Event Venue

Sydney

Repository Status

  • Restricted

Socio-economic Objectives

Maritime; International sea freight transport (excl. live animals, food products and liquefied gas); Expanding knowledge in engineering

Usage metrics

    University Of Tasmania

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC