20.500.12556/DiRROS-23176 A numerical study of double flow focusing micro-jets 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. serial femtosecond crystallography sample delivery double flow focusing water–ethanol mixing jet properties finite volume method volume of fluid serijska femtosekundna kristalografija dostava vzorcev dvojno fokusiranje toka mešanje vode in etanola metoda končnih volumnov true false true Emerald Publishing Limited International journal of numerical methods for heat & fluid flow Angleški jezik Slovenski jezik © Rizwan Zahoor, Saša Bajt and Božidar Šarler Neznano 2025-08-05 09:19:38 2025-08-05 09:19:39 2025-10-24 03:53:27 0000-00-00 00:00:00 2025 0 0 str. 1983-2003 iss. 6 Vol. 35 2025 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 2025-06-23 532:519.6 0961-5539 10.1108/HFF-07-2024-0480 212394755 RAZ_Zahoor_Rizwan_2025.pdf RAZ_Zahoor_Rizwan_2025.pdf 1 2EA78467A790FA2F613D74E7F98FA335 e550c2aa2ba135bc012a42dc245d5b0f773bceb287fd03c253c46ca481305bd6 c8d9d71d-71ce-11f0-9bb7-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=34062 https://www.emerald.com/hff/article/35/6/1983/1252879/A-numerical-study-of-double-flow-focusing-micro 1 8e918537-71cc-11f0-9bb7-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=34061 Inštitut za kovinske materiale in tehnologije 0 0 0