Abstract The work focuses on the calibration of cavitation model parameters for the numerical simulation of three-phase injector flows. Cavitation is modeled through a transport equation for the void fraction closed by the Schnerr-Sauer relation. The vaporization and condensation factors contained in this model are considered for calibration against experimental data available for a test-case characterized by fuel injection in a reservoir filled of air through an axisymmetric channel. In spite of the simplified geometry, this flow configuration is representative of a real injector and contains most of the complex physical phenomena which may be encountered in injector flows, as turbulence, cavitation and hydraulic flip, i.e. a back flow of air from outside the injector along the whole length of the channel replacing the cavitating regions. Since a direct calibration would imply huge computational costs, not affordable in practical applications, response surfaces of the quantities of interest are built through generalized Polynomial Chaos. These response surfaces, which can be obtained starting from only a few deterministic simulations, have been then used to carry out the parameter calibration. The quantities of interest taken into consideration are the critical cavitation point (CCP), i.e. the value of the outlet pressure at which the flow inside the injector can be considered choked (for a fixed inlet pressure), and the mass-flow-rate (MFR) at the CCP. To further reduce the computational costs, calibration is carried out by using axisymmetric simulations. It has been then checked that the obtained cavitation model gives accurate results also in three-dimensional simulations of the actual geometry. Moreover, this set-up has been applied to two different complex one-hole injector geometries, i.e. a sector of real injector geometries, and the results have been compared against available experimental data. The calibrated cavitation model set-up appears to be robust, giving good predictions also in conditions significantly different from those in which it has been obtained.

中文翻译：

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用于模拟三相喷射器内部流动的空化模型参数的随机校准

摘要 工作的重点是用于三相喷射器流动数值模拟的空化模型参数的标定。空化通过 Schnerr-Sauer 关系闭合的空隙率的输运方程建模。该模型中包含的汽化和冷凝因子被考虑用于校准与可用于测试用例的实验数据，该测试用例的特征是燃料通过轴对称通道注入充满空气的储器中。尽管具有简化的几何形状，但这种流动配置代表了真实的喷射器，并且包含了喷射器流动中可能遇到的大多数复杂物理现象，如湍流、空化和液压翻转，即喷射器外部的空气回流沿着通道的整个长度替换空化区域。由于直接校准将意味着巨大的计算成本，在实际应用中无法承受，因此通过广义多项式混沌构建感兴趣量的响应面。这些响应面可以从几个确定性的模拟开始获得，然后被用来进行参数校准。考虑的重要数量是临界空化点 (CCP)，即喷射器内部的流动可以被视为阻塞的出口压力值（对于固定的入口压力），以及质量流量（ MFR) 在 CCP。为了进一步降低计算成本，通过使用轴对称模拟进行校准。然后已经检查所获得的空化模型在实际几何形状的三维模拟中也给出了准确的结果。此外，该设置已应用于两种不同的复杂单孔注入器几何形状，即实际注入器几何形状的一部分，并且已将结果与可用的实验数据进行了比较。校准的空化模型设置似乎很稳健，在与获得的条件明显不同的条件下也能给出良好的预测。