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Experimental investigation of cavitation induced air release

Kowalski, Karoline ; Pollak, Stefan ; Hussong, Jeanette (2017):
Experimental investigation of cavitation induced air release. (Publisher's Version)
In: EPJ Web of Conferences, 143, pp. 1-5. EDP Sciences, ISSN 2100-014X,
DOI: 10.25534/tuprints-00014267,
[Article]

Abstract

Variations in cross-sectional areas may lead to pressure drops below a critical value, such that cavitation and air release are provoked in hydraulic systems. Due to a relatively slow dissolution of gas bubbles, the performance of hydraulic systems will be affected on long time scales by the gas phase. Therefore predictions of air production rates are desirable to describe the system characteristics. Existing investigations on generic geometries such as micro-orifice flows show an outgassing process due to hydrodynamic cavitation which takes place on time scales far shorter than diffusion processes. The aim of the present investigation is to find a correlation between global, hydrodynamic flow characteristics and cavitation induced undissolved gas fractions generated behind generic flow constrictions such as an orifice or venturi tube. Experimental investigations are realised in a cavitation channel that enables an independent adjustment of the pressure level upstream and downstream of the orifice. Released air fractions are determined by means of shadowgraphy imaging. First results indicate that an increased cavitation activity leads to a rapid increase in undissolved gas volume only in the choking regime. The frequency distribution of generated gas bubble size seems to depend only indirectly on the cavitation intensity driven by an increase of downstream coalescence events due to a more densely populated bubbly flow.

Item Type: Article
Erschienen: 2017
Creators: Kowalski, Karoline ; Pollak, Stefan ; Hussong, Jeanette
Origin: Secondary publication via Golden Open Access
Status: Publisher's Version
Title: Experimental investigation of cavitation induced air release
Language: English
Abstract:

Variations in cross-sectional areas may lead to pressure drops below a critical value, such that cavitation and air release are provoked in hydraulic systems. Due to a relatively slow dissolution of gas bubbles, the performance of hydraulic systems will be affected on long time scales by the gas phase. Therefore predictions of air production rates are desirable to describe the system characteristics. Existing investigations on generic geometries such as micro-orifice flows show an outgassing process due to hydrodynamic cavitation which takes place on time scales far shorter than diffusion processes. The aim of the present investigation is to find a correlation between global, hydrodynamic flow characteristics and cavitation induced undissolved gas fractions generated behind generic flow constrictions such as an orifice or venturi tube. Experimental investigations are realised in a cavitation channel that enables an independent adjustment of the pressure level upstream and downstream of the orifice. Released air fractions are determined by means of shadowgraphy imaging. First results indicate that an increased cavitation activity leads to a rapid increase in undissolved gas volume only in the choking regime. The frequency distribution of generated gas bubble size seems to depend only indirectly on the cavitation intensity driven by an increase of downstream coalescence events due to a more densely populated bubbly flow.

Journal or Publication Title: EPJ Web of Conferences
Journal volume: 143
Publisher: EDP Sciences
Divisions: 16 Department of Mechanical Engineering
16 Department of Mechanical Engineering > Fluid Mechanics and Aerodynamics (SLA)
Date Deposited: 30 Nov 2020 15:42
DOI: 10.25534/tuprints-00014267
Official URL: https://tuprints.ulb.tu-darmstadt.de/14267
URN: urn:nbn:de:tuda-tuprints-142676
Additional Information:

EFM16 – Experimental Fluid Mechanics 2016

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