Flash atomization can occur in rocket thrusters operated at near vaccum conditions just prior to ignition when cryogenic propellants are injected into the reaction chamber. Although the morphology of flashing sprays has been widely studied, empirical observations of the primary breakup mechanisms at the micro-scale are currently not feasible. Still, further analysis of the micro-scales is necessary for development of closure models in both empirical and numerical models. In this work direct numerical simulations are performed to provide insight into the microscopic processes that dominate the dynamics of the primary atomization. We use a multiphase solver (FS3D) based on the volume of fluid method and PLIC reconstruction to track the liquid-vapour interface with high fidelity, fully resolving viscous and capillary effects. Thermodynamic effects are introduced by calibration of the fluid properties and evaporation rate to a target range of thermodynamic conditions and nuclei number density. The use of an affordable incompressible scheme allows for highly resolved simulations comprising up to thousand bubbles across a range of Weber and Ohnesorge numbers. Using a randomized bubble arrangement it is generally observed that the qualitative characterization of the breakup dynamics corroborates previous results using regular bubble arrays. However, these differ substantially from the simplified mechanics hypothesised in the literature. A temporal analysis of the breakup provides estimates for the rate of change in the spray surface area and volume fraction. The droplet size distributions are compared in terms of droplet number, surface area and volume fraction. A model based on the thermodynamic conditions is proposed to estimate the SMD for different Weber numbers.

当低温推进剂被注入反应室时，在点火之前在接近真空条件下运行的火箭推进器中可能会发生闪光雾化。尽管闪蒸喷雾的形态已被广泛研究，但目前在微观尺度上对主要破裂机制的经验观察尚不可行。尽管如此，对微观尺度的进一步分析对于在经验模型和数值模型中开发闭合模型是必要的。在这项工作中，进行了直接的数值模拟，以深入了解主导初级雾化动力学的微观过程。我们使用基于流体体积法和 PLIC 重建的多相求解器 (FS3D) 以高保真度跟踪液-气界面，完全解析粘性和毛细管效应。通过将流体特性和蒸发率校准到热力学条件和核数密度的目标范围来引入热力学效应。使用负担得起的不可压缩方案可以进行高分辨率的模拟，其中包括跨越一系列 Weber 和 Ohnesorge 数的多达数千个气泡。使用随机气泡排列，通常观察到破碎动力学的定性表征证实了先前使用规则气泡阵列的结果。然而，这些与文献中假设的简化力学大不相同。分解的时间分析提供了对喷雾表面积和体积分数变化率的估计。在液滴数量、表面积和体积分数方面比较液滴尺寸分布。