Numerical investigation on influence of focusing gas type on liquid micro-jet characteristics

Abstract

Liquid micro-jets, produced from gas dynamic virtual nozzles (GDVNs), are used as sample carriers for interaction with X-ray beam in serial femtosecond crystallography (SFX). A numerical investigation of the effect of the focusing gas type on the liquid micro-jet properties (its length and thickness) is presented. The study complements our previous research on the influence of operating conditions and the nozzle geometry on GDVN performance. The influence of helium, argon, carbon dioxide and nitrogen gases (at a fixed mass flow rate of 1.6 × 104 mg/min) on focusing pure water jet (flow rate of 33 µl/min) is analysed. An experimentally validated numerical model, based on laminar two-phase Newtonian compressible flow with ideal gas assumption, finite volume method and volume of fluid interface tracking, is used. Helium is found to be the most suitable gas among the tested ones for producing thin, long and fast jets. The study provides a basis for the focusing gas selection in SFX experiments.