Investigation of Supersonic Focusing Gas Velocity on Micro-jet CharacteristicsMalik, Ahsan Afzaal (Avtor) Šarler, Božidar (Mentor) Serial femtosecond crystallographyMicro-jetFlow focusingConverging-diverging nozzleFinite volume methodVolume of fluid formulationTwo-phase flowComputational fluid dynamics.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.[Malik A. A.] 20192019-03-02 07:45:27Magistrsko delo/naloga106533sl