Abstract Compressible multiphase numerical simulations of gas-focused micro-jets are compared with the experimental data obtained with the dual pulse imaging laser-induced fluorescence drop velocimetry. Such jets, originating from a 3D printed gas dynamic virtual nozzle into a low-vacuum (150 Pa) environment, are increasingly being used for sample delivery in serial femtosecond crystallography. The distance traveled by a detaching drop from the jet is measured between the two consecutive illumination pulses with a known time delay at the positions 200 µm and 450 µm from the nozzle. Additionally, the high-speed camera images are used to analyze the shape of the jet. An axisymmetric, compressible, Newtonian two-phase helium-water mixture model is numerically solved within the framework of the volume of fluid and the finite volume method. The experimental and the computational studies are performed with a constant volumetric liquid flow rate of 14 μl/min and the gas mass flow rate in the range from 4.6 mg/min to 20 mg/min. The related jet Reynolds number ranges from 120 to 220 and Weber number from 30 to 150. The maximum difference between the measurements and the results of the numerical model in terms of the droplet velocity and jet diameter is within 10 %. The study provides new information on the jet velocities for micron-sized gas-focused nozzles. The validated numerical model can be used as a design tool for the nozzles dedicated to the specific needs of the femtosecond crystallography experiments.

中文翻译：

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气体聚焦液体微射流速度的实验与数值研究

摘要 将气体聚焦微射流的可压缩多相数值模拟与双脉冲成像激光诱导荧光液滴测速仪获得的实验数据进行了比较。这种射流源自 3D 打印的气体动态虚拟喷嘴，进入低真空 (150 Pa) 环境，越来越多地用于串行飞秒晶体学中的样品输送。在距离喷嘴 200 µm 和 450 µm 的位置具有已知时间延迟的两个连续照明脉冲之间测量从射流中分离的液滴行进的距离。此外，高速摄像机图像用于分析射流的形状。在流体体积和有限体积法的框架内，对轴对称、可压缩、牛顿两相氦水混合物模型进行了数值求解。实验和计算研究以 14 μl/min 的恒定体积液体流速和 4.6 mg/min 至 20 mg/min 的气体质量流速进行。相关射流雷诺数范围为 120 到 220，韦伯数范围为 30 到 150。测量值与数值模型结果在液滴速度和射流直径方面的最大差异在 10% 以内。该研究为微米级气体聚焦喷嘴的射流速度提供了新信息。经验证的数值模型可用作专用于飞秒晶体学实验特定需求的喷嘴的设计工具。相关的射流雷诺数范围为 120 到 220，韦伯数范围为 30 到 150。测量值与数值模型结果在液滴速度和射流直径方面的最大差异在 10% 以内。该研究为微米级气体聚焦喷嘴的射流速度提供了新信息。经验证的数值模型可用作专用于飞秒晶体学实验特定需求的喷嘴的设计工具。相关的射流雷诺数范围为 120 到 220，韦伯数范围为 30 到 150。测量值与数值模型结果在液滴速度和射流直径方面的最大差异在 10% 以内。该研究为微米级气体聚焦喷嘴的射流速度提供了新信息。经验证的数值模型可用作专用于飞秒晶体学实验特定需求的喷嘴的设计工具。