Process intensification by cavitation is gaining widespread attention due to the benefits that the intense bubble collapse conditions can provide, yet, several knowledge gaps exist in the modelling of such systems. This work studies the numerical prediction of single bubble dynamics and the various approaches that can be employed to estimate the changes in the chemical composition of cavitating bubbles. Specific emphasis is placed on the prediction of the radical production rates during bubble collapse and the computational performance, with the aim of coupling the single bubble dynamics to flow models for reactor hydrodynamics. The results reveal that the choice of chemical reaction approach has virtually no effect on the bubble dynamics, whereas the predicted radical production rates can differ substantially. It is found that evaluating the radical production only on temperature peaks, an approach commonly followed in literature, may result in the most erroneous estimations (on average 12.8 times larger than those of the full kinetic model), while a simplified kinetic model yields more accurate predictions (2.3 times larger) at the expense of increased computational times. Continuous evaluation of the bubble content by assuming equilibrium when the bubble temperature is above a certain threshold () is shown to be capable of predicting total radical production values close to those estimated by solving the kinetics of a detailed reaction model (19.8% difference), as well as requiring only 22.2% more computational costs compared to simulations without chemical reaction modelling. Such an equilibrium approach is therefore recommended for future studies aiming to couple flow simulations with single bubble dynamics to accurately predict radical production rates in cavitation devices, involving numerous bubbles following different flow trajectories. Furthermore, an algebraic expression that successfully approximates the full kinetic simulation results is proposed as a function of the initial nucleus size and the time integral of the liquid pressure when it is under vapor pressure. Such a model can be applied in modelling efforts that do not require local instantaneous radical concentrations, and paves the way for efficient closure modelling of radical production in CFD simulations of hydrodynamic reactors.

中文翻译：

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空化辅助反应器中自由基产生的有效建模

由于强烈的气泡破裂条件可以提供的好处，空化过程强化正受到广泛关注，然而，在此类系统的建模中存在一些知识空白。这项工作研究了单个气泡动力学的数值预测以及可用于估计空化气泡化学成分变化的各种方法。特别强调气泡破裂过程中自由基生产率的预测和计算性能，目的是将单个气泡动力学与反应器流体动力学的流动模型耦合起来。结果表明，化学反应方法的选择实际上对气泡动力学没有影响，而预测的自由基生产率可能有很大差异。研究发现，仅在温度峰值上评估自由基产生（文献中普遍采用的一种方法）可能会导致最错误的估计（平均比完整动力学模型大 12.8 倍），而简化的动力学模型会产生更准确的估计预测（大 2.3 倍），但代价是计算时间增加。当气泡温度高于某个阈值 () 时，通过假设达到平衡来连续评估气泡含量，能够预测总自由基生成值，该值接近通过求解详细反应模型的动力学估计的值（差异为 19.8%），与没有化学反应建模的模拟相比，仅需要多 22.2% 的计算成本。因此，建议未来研究采用这种平衡方法，旨在将流动模拟与单个气泡动力学结合起来，以准确预测空化装置中的自由基生产率，其中涉及遵循不同流动轨迹的大量气泡。此外，还提出了一种成功地近似全动力学模拟结果的代数表达式，作为初始核尺寸和蒸汽压力下液体压力的时间积分的函数。这种模型可应用于不需要局部瞬时自由基浓度的建模工作，并为水力反应器 CFD 模拟中自由基产生的有效闭合建模铺平了道路。