湍流中小液滴的碰撞与聚并实验研究

湍流中的小液滴／颗粒的动力学可应用于许多工业及天气和气候科学。其中受关注的有湍流如何增强液滴碰撞与聚并的问题。目前，用实验来研究该问题仍在技术上有相当难度，属于多相流体力学实验的前沿性问题之一。但是为了验证已有的理论和在数值模拟中简化模型的正确性，获取系统性的实验数据确是很有必要的。本申请拟实现可用于研究各种湍流中液滴/粒子动力学问题的湍流室实验方案 。通过实验，我们拟研究如下问题：液滴碰撞与聚并率与主要的流动参数（如雷诺数，斯托克斯数等）及流动各向异性有怎样的联系？ 不同尺寸的液滴间的碰撞-聚并的统计量与相同尺寸液滴间的行为有什么不同？碰撞发生的统计量和粒子的基本统计量，如径向分布函数及粒子相对速度分布是怎样联系的？这些结果将会丰富我们对湍流中液滴/粒子行为的认识，可用来验证现有的理论与数值模拟结果，并推动理论与模型的进一步发展。

Dynamical behavior of small particles and droplets under the influence of turbulent flows have important implications for many technological-industrial application and weather-climate science. Of particular interest is the phenomena of turbulent enhanced particle collision and droplet coalescence. Experiments to study this phenomena is technically challenging and is at the forefront of multiphase fluid mechanical experiments. Nevertheless, there is a strong need of systematic experimental data in order to validate available theories and simplified models used in numerical simulation. In this proposal, we will construct an advanced turbulent chamber facility that could be used for various studies of droplet/particle dynamics in turbulent flows. We will conduct experiments to study: how droplet collision and coalescence rates depends on major flow parameters (Reynolds, Stokes, Froude number) and flow anisotropy; how statistics of collision-coalescence between droplets of different sizes differ from those of single sized; how collision statistics relates to other particles statistics (e.g. radial distribution function and relative velocity distribution). Our findings will be used to test the validity of available theories and simulations and will likely inspire further improvements to these theories and models.