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Investigation of Supersonic Focusing Gas Velocity on Micro-jet Characteristics
Malik, Ahsan Afzaal (Author), Šarler, Božidar (Mentor) More about this mentor... This link opens in a new window

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Abstract
Liquid micro-jets, produced from gas dynamic virtual nozzles, are used as sample carriers for interaction with X-ray free electron laser beam in serial femtosecond crystallography (SFX). A numerical investigation on the influence of Converging-Diverging (CD) nozzle design on formation of liquid micro-jet for SFX experiments is performed. The characteristics of micro-jets (jet length, thickness and velocity) from four CD nozzles with different diverging section lengths and angles are compared with the characteristics of micro-jets from standard converging nozzle. Distilled water jet with a flow rate of 30 μl/min is focused with Helium gas at a fixed mass flow rate 30 mg/min while changing the length and the angle of the diverging section of CD nozzle. The two-phase flow problem in discussion is modelled based on mixture formulation of Newtonian compressible flow, under assumption of Helium as an ideal gas and water as incompressible. The volume of fluid formulation is used to track the interphase boundary and the finite volume method is used for the numerical solution. OpenFOAM code with solver compressibleMultiphaseInterFoam is used for simulating the flow whereas ParaView and Matplotlib are used to post-process the data. The analyses is performed to assess whether the jet thickness is reduced and the jet length is longer because of the added diverging section. We discover that for all four cases with CD nozzles, the jet diameter is 0.75 - 0.85 μm smaller as compared to the converging nozzle jet thickness 4.45 μm. The jet length is longer by 20 - 160 μm with respect to the converging nozzle jet length 497.3 μm, whereas the jet velocity along the centreline of the jet shows an increase of 15 - 20 m/s for CD nozzle with respect to 48 m/s for converging nozzle. This study can serve as a basis for further computational design of CD nozzles with other geometries, operating conditions and other liquids and gases.

Language:Slovenian
Keywords:Serial femtosecond crystallography, Micro-jet, Flow focusing, Converging-diverging nozzle, Finite volume method, Volume of fluid formulation, Two-phase flow, Computational fluid dynamics.
Work type:Master's thesis/paper (mb22)
Tipology:2.09 - Master's Thesis
Organization:FS - Faculty of Mechanical Engineering
Year:2019
Publisher:[Malik A. A.]
Number of pages:XXI, 67 str.
UDC:004.942:519.876.5+621.3.02(043.2)
COBISS.SI-ID:16549403  Link is opened in a new window
Views:383
Downloads:126
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Secondary language

Language:English
Title:Analiza vpliva nadzvočne hitrosti usmerjevalnega plina na značilnosti mikrocurka
Abstract:
Kapljevinski mikrocurki, proizvedeni z uporabo plinskih dinamičnih navideznih šob, se uporabljajo kot nosilci vzorcev za interakcijo z X-žarki iz laserjev na proste elektrone v serijski femtosekundni kristalografiji (SFX). Izdelana je numerična raziskava vpliva konstrukcije konvergentno divergentne (CD) šobe na formacijo mikrocurkov za SFX eksperimente. Karakteristike (dolžina, debelina in hitrost curka) mikrocurkov iz štirih CD šob z različnimi dolžinami in koti divergentnega dela so primerjani s karakteristikami mikocurkov iz standardne konvergentne šobe. Destilirana voda s pretokom 30 ml/min je fokusirana z uporabo helijevega plina konstantnega masnega toka 30 mg/min pri spremenljivi dolžini in kotu divergenčnega dela CD šobe. Obravnavani primer dvofaznega toka je modeliran na osnovi formulacije mešanice dvofaznega stisljivega Newtonskega toka, pri predpostavki, da je helij idealen plin in voda nestisljiva. Za sledenje medfaznemu robu je uporabljana formulacija volumna tekočine, metoda kotrolnih prostornin pa je uporabljena za numerično rešitev. Simulacije so izvedene s pomočjo programa OpenFOAM z reševalnikom compressibleMultiphaseInterFoam, medtem ko sta ParaView in Matplotlib uporabljena za naknadno obdelavo podatkov. Analiza je izvedena, da bi ocenili, ali se z uporabo dodatnega divergenčnega dela šobe debelina curka zmanjšana in se dolžina curka podaljša. Ugotovili smo, da je pri vseh štirih primerih s CD šobami premer curka za 0,75 - 0,85 μm manjši v primerjavi z debelino curka konvergentne šobe 4,45 μm. Dolžina curka je daljša za 20 - 160 μm glede na dolžino curka konvergenčne šobe 497,3 μm, medtem ko je hitrost curka vzdolž srednjice curka povečana za 15 - 20 m/s pri CD šobi glede na 48 m/s pri konvergentni šobi. Ta študija lahko služi kot osnova za nadaljnje računalniško podprto načrtovanje CD šob z drugimi geometrijami, pogoji delovanja in drugimi tekočinami in plini.

Keywords:serijska femtosekundna kristalografija, mikrocurek, usmerjanje toka, konvergentno-divergentna šoba, metoda kontrolnih prostornin, formulacija volumna tekočine, dvofazni tok, računalniška dinamika tekočin.

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