A numerical study of double flow focusing micro-jets

Zahoor, Rizwan (author), Bajt, Saša (author), Šarler, Božidar (author)

Purpose: Double flow-focusing nozzles (DFFNs) form a coaxial flow of primary liquid with microcrystalline samples, surrounded by secondary liquid and focusing gas. This paper aims to develop an experimentally validated numerical model and assess the performance of micro-jets from a DFFN as a function of various operating parameters for the water–ethanol–helium system, revealing the jet's stability, diameter, length and velocity. Design/methodology/approach: The physical model is formulated in the mixture-continuum formulation, which includes coupled mass, momentum and species transport equations. The model is numerically formulated within the finite volume method–volume of fluid approach and implemented in OpenFOAM to allow for a non-linear variation of the fluid's material properties as a function of the mixture concentration. The numerical results are compared with the experimental data. Findings: A sensitivity study of jets with Reynolds numbers between 12 and 60, Weber numbers between 4 and 120 and capillary numbers between 0.2 and 2.0 was performed. It was observed that jet diameters and lengths get larger with increased primary and secondary fluid flow rates. Increasing gas flow rates produces thinner, shorter and faster jets. Previously considered pre-mixed and linear mixing models substantially differ from the accurate representation of the water–ethanol mixing dynamics in DFFNs. The authors demonstrated that Jouyban–Acree mixing model fits the experimental data much better. Originality/value: The mixing of primary and secondary liquids in the jet produced by DFFN is numerically modelled for the first time. This study provides novel insights into mixing dynamics in such micro-jets, which can be used to improve the design of DFFNs.

• Language: English
• Keywords: serial femtosecond crystallography, sample delivery, double flow focusing, water–ethanol mixing, jet properties, finite volume method, volume of fluid
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: Str. 1983-2003
• Numbering: Vol. 35, iss. 6
• PID: 20.500.12556/RUL-170949
• UDC: 532:519.6
• ISSN on article: 0961-5539
• DOI: 10.1108/HFF-07-2024-0480
• COBISS.SI-ID: 212394755
• Publication date in RUL: 23.07.2025

Record is a part of a journal

• Title: International journal of numerical methods for heat & fluid flow
• Publisher: Emerald
• ISSN: 0961-5539
• COBISS.SI-ID: 15153413

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: serijska femtosekundna kristalografija, dostava vzorcev, dvojno fokusiranje toka, mešanje vode in etanola, metoda končnih volumnov