Next generation spray simulation model (NGSSM)

喷雾是一系列技术中的核心现象，包括医疗吸入器，表面涂层，电子冷却，汽车工程中的燃油喷射器以及制药应用中的干粉生产。准确预测液滴动力学、液滴分布及其在空间和时间上的蒸汽浓度对于提高基于喷雾的技术的效率至关重要。该项目的重点是开发一种新的工具来模拟工程应用中的喷雾。新颖之处在于数学和数值模拟技术的综合和发展，以期应用于工程应用。传统的液滴建模是基于跟踪单个液滴或小群液滴（包裹）。这个项目将通过开发一种基于液滴大小分布的新的数学形式，将科学提升到一个新的水平。这将导致一种新的喷雾模拟策略，并将围绕液滴分布在空间和时间上的演变建模。反过来，这将确保新模型在计算液滴浓度时比传统的跟踪方法更有效。该模型将考虑液滴的蒸发和冷凝、液滴的多分散性、液滴对气体流动的影响以及湍流。将开发新的数值模拟方法，以确保高效、快速、稳健和准确的计算。研究的另一个方向将集中在开发一种方法上，该方法将把喷射器喷嘴附近的密集喷雾和远离喷嘴和液体核心的稀释气体和液滴混合物的建模联系起来。有一组方法专注于近喷嘴区域的建模，并基于捕获/跟踪液气界面。当将这些方法与液滴动力学联系起来以获得喷雾的完整建模时，人们获得了液滴形成，位置和动力学的确定性描述。与此相反，我们建议开发一种基于液滴尺寸分布公式的新模型。在喷嘴附近密集喷雾为欧拉-拉格朗日混合模型，下游为完全拉格朗日模型。这将是对整个过程进行建模的重要一步：从喷雾形成到液滴蒸发或沉积。这种方法对于液滴分布及其沉积以及液滴蒸气对最终产品质量很重要的应用特别有用，例如表面加工/涂层。新模型将通过平板风机注水实验数据进行验证。新的实验将侧重于液滴的空间分布和液滴的大小分布。在验证后，我们将对该模型进行调整和测试，用于两种应用：压力计量吸入器和燃油喷射。第一项研究将在Pannala博士（生物材料和医疗设备以及药物输送研究和企业集团）的咨询下完成。第二个将与工业合作伙伴里卡多英国有限公司协商进行。该项目的主要目标是开发一种产品，该产品将准备使用，与传统的计算流体动力学软件兼容，并将为工程应用提供先进的喷雾现象模拟。要开发的数字代码将作为开源和免费软件OpenFOAM的库来实现。图书馆的最终版本将在麻省理工学院许可下通过在线布莱顿研究数据存储库发布。因此，该项目的成果将为对喷雾现象感兴趣的研究人员和工程师提供广泛的社区。

Spray is a core phenomenon in a range of technologies, including medical inhalers, surface coating, electronics cooling, fuel injectors in automotive engineering, and the production of dry powder in pharmaceutical applications. Accurate predictions of droplet dynamics, distribution of droplets and their vapour concentration in space and time are essential for making technologies based on sprays more efficient. The focus of the project is on the development of a novel tool to simulate sprays for engineering applications. The novelty lies in the synthesis and development of mathematical and numerical modelling techniques with the view to be applied to engineering applications. Conventional modelling of droplets is based on tracking individual droplets or small groups of droplets (parcels). This project will take the science to a new level by developing a new mathematical formalism that will be based on droplet size distribution. This will lead to a new strategy for simulation of sprays and will be built around modelling of the evolution of droplet distribution in space and time. This, in turn, will ensure that the new model is computationally more efficient for calculating droplet concentrations than the conventional tracking method. The model will take into account droplet evaporation and condensation, polydispersity of droplets, effect of droplets on the gas flow, and turbulence. Novel approaches in numerical modelling will be developed to ensure efficient, fast, robust and accurate calculations. Another direction of the research will be focused on development of a methodology that will link modelling dense spray near the injector nozzle and dilute mixture of gas and droplet further away from the nozzle and the liquid core. There is a group of methods that focus on modelling of the near-nozzle region and are based on capturing/tracking the liquid-gas interface. When linking these methods with droplet dynamics to obtain the full modelling of spray, one obtains a deterministic description of droplet formation, location and dynamics. In contrast to this, we propose to develop a new model that will be based on droplet size distribution formulation. It will be a hybrid Eulerian-Lagrangian model for dense spray near nozzle and fully Lagrangian model downstream. This will be a significant step forward to modelling of the full process: from spray formation to droplet evaporation or deposition. This approach will be particularly useful for applications where distribution of droplets and their deposits, as well as of droplet vapour, are important for end-product quality, for example surface processing/coating. The new model will be validated against experimental data obtained for a flat fan water injection. The new experiments will focus on droplet spatial distribution as well as droplet size distribution. After validation, we will adapt and test the model for two applications: pressurised-metered dose inhaler and fuel injection. The first study will be done in consultation with Dr Pannala (Biomaterials and Medical Devices and Drug Delivery Research and Enterprise Group). The second one will be conducted in consultation with the industrial partner Ricardo UK Ltd. The main goal of the project is to develop a product, which will be ready to use, compatible with conventional computational fluid dynamics software, and that will enable advanced simulation of spray phenomena for engineering applications. The numerical code to be developed will be implemented as a library to open-source and freely available software OpenFOAM. The final version of the library will be distributed under the MIT license via the online Brighton Research Data Repository. Thus the outcomes of the project will be accessible to a wide community of researchers and engineers interested in spray phenomena.