Finite-size particles interacting with non-homogeneous turbulence

分散两相流出现在许多工业应用和自然现象中，从海洋中运输的塑料到发动机中的喷雾。塑料传输预测或推进的效率和环境影响取决于预测和控制包含重颗粒的流动的能力，这些颗粒受到重力和湍流的综合作用。小于最小流动长度尺度的惯性颗粒的湍流输运已经得到了广泛的研究，但是密度适度大于流体且存在重力的有限尺寸颗粒的情况仅在较小程度上进行了探索，因此仍然存在大量的未决问题：载体流湍流如何影响中等重量的有限尺寸颗粒的运动？它们如何沿着沿着对湍流速度场进行采样，以及它们的沉降速度是多少？它们会形成团簇吗？当它们的浓度增加时，它们是如何影响载流子湍流的？这些知识差距目前阻碍了为工程目的建立预测模型的进一步进展。本项目建议研究这些影响与尖端的实验技术和完全解决直接数值模拟联合收割机结合两种方法的优点：覆盖范围广泛的参数与部分信息的实验与数量较少的完全耦合的数值模拟提供完整的信息。这将允许研究从系统大小到粒子周围近场中非常小尺度的动力学，并对能量平衡进行清晰的解释。这种方法将导致数据覆盖的第一次广泛的参数空间（颗粒尺寸，密度比，伽利略和雷诺数，固体体积分数）。可以预期的结果，以推进我们的知识和建模的粒子湍流相互作用的动力学显着。

Dispersed two-phase flows occur in many industrial applications and natural phenomena, ranging from plastic transported in oceans, to sprays in engines. Plastic transport prediction or efficiency and environmental impact of propulsion depend on the ability to predict and control flows containing heavy particles which are submitted to the combined action of gravity and turbulence. The turbulent transport of inertial particles smaller than the smallest flow length-scale has been widely investigated, but the case of finite-size particles with density moderately larger than the fluid and in the presence of gravity has only been explored to a much lesser extent, so that a significant number of open questions remain: how does the carrier flow turbulence affect the motion of moderately heavy, finite-size particles? How do they sample the turbulent fluid velocity field along their trajectory, and what is their settling velocity? Do they form clusters, and how do they affect the carrier turbulence when their concentration increases? These knowledge gaps are currently blocking further progress towards predictive models for engineering purposes. The present project proposes to study these effects with cutting-edge experimental techniques and fully resolved direct numerical simulation to combine the advantages of the two approaches: covering a wide range of parameters with partial information in experiments with a smaller number of fully coupled numerical simulations providing full information. This will allow to investigate dynamics from the system size down to the very small scales in the near-field around the particles with clear interpretation of the energy balance. This approach will lead to data covering for the first time a wide parameter space (particle size, density ratio, Galileo and Reynolds numbers, solid volume fraction). The results can be expected to advance our knowledge and the modelling of the dynamics of particle-turbulence interaction significantly.