Purpose

This study aims to develop an experimentally validated three-dimensional numerical model for predicting different flow patterns produced with a gas dynamic virtual nozzle (GDVN).

Design/methodology/approach

The physical model is posed in the mixture formulation and copes with the unsteady, incompressible, isothermal, Newtonian, low turbulent two-phase flow. The computational fluid dynamics numerical solution is based on the half-space finite volume discretisation. The geo-reconstruct volume-of-fluid scheme tracks the interphase boundary between the gas and the liquid. To ensure numerical stability in the transition regime and adequately account for turbulent behaviour, the k-ω shear stress transport turbulence model is used. The model is validated by comparison with the experimental measurements on a vertical, downward-positioned GDVN configuration. Three different combinations of air and water volumetric flow rates have been solved numerically in the range of Reynolds numbers for airflow 1,009–2,596 and water 61–133, respectively, at Weber numbers 1.2–6.2.

Findings

The half-space symmetry allows the numerical reconstruction of the dripping, jetting and indication of the whipping mode. The kinetic energy transfer from the gas to the liquid is analysed, and locations with locally increased gas kinetic energy are observed. The calculated jet shapes reasonably well match the experimentally obtained high-speed camera videos.

Practical implications

The model is used for the virtual studies of new GDVN nozzle designs and optimisation of their operation.

Originality/value

To the best of the authors’ knowledge, the developed model numerically reconstructs all three GDVN flow regimes for the first time.

中文翻译：

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气体动态虚拟喷嘴滴流、喷射、鞭打模式数值模拟及实验验证

目的

本研究旨在开发一种经过实验验证的三维数值模型，用于预测气体动态虚拟喷嘴（GDVN）产生的不同流动模式。

设计/方法论/途径

物理模型是在混合物配方中提出的，用于处理不稳定、不可压缩、等温、牛顿、低湍流两相流。计算流体动力学数值解基于半空间有限体积离散。地质重建流体体积方案跟踪气体和液体之间的相界面。为了确保过渡状态的数值稳定性并充分考虑湍流行为，使用 k-ω 剪切应力传递湍流模型。通过与垂直、向下定位的 GDVN 配置上的实验测量结果进行比较，该模型得到了验证。空气和水体积流量的三种不同组合已在雷诺数范围内数值求解，气流分别为 1,009-2,596，水为 61-133，韦伯数为 1.2-6.2。

发现

半空间对称性允许对滴落、喷射和搅打模式的指示进行数值重建。分析从气体到液体的动能传递，并观察气体动能局部增加的位置。计算出的射流形状与实验获得的高速摄像机视频相当吻合。

实际影响

该模型用于新 GDVN 喷嘴设计及其操作优化的虚拟研究。

原创性/价值

据作者所知，所开发的模型首次以数值方式重建了所有三种 GDVN 流态。