圆管湍流中颗粒沉积的朗之万PDF模拟
Langevin PDF simulation of particle deposition in a turbulent pipe flow
摘要：
本文用朗之万PDF模型描述了大范围颗粒直径的湍流中颗粒在壁面上的沉积。本工作的第一个目的是测试目前的朗之万模型是如何能够描述这种现象，并概述的物理方面，在粒子沉积中发挥主要作用。首先回顾了目前随机模型的一般特征和特点。然后，所获得的结果与标准形式的模型一起进行了分析，以检查不同的平均流体量的预测的灵敏度。这些结果表明，近壁物理的物理表示有待改进，特别是一条可能的途径是引入与近壁相干结构有关的特殊特征。在下文中，我们提出了一个简单的唯象模型，该模型引入了由于湍流相干结构对靠近壁的薄层中的颗粒的存在而产生的一些影响。用这种现象学模型得到的结果与实验证据吻合得很好，这表明在这个方向上，朝着更一般和更严格的随机模型的发展，提供了一个湍流的几何描述和统计之间的联系。
英文摘要：
The paper deals with the description of particle deposition on walls from a turbulent flow over a large range of particle diameter, using a Langevin PDF model. The first aim of the work is to test how the present Langevin model is able to describe this phenomenon and to outline the physical as- pects which play a major role in particle deposition. The general features and characteristics of the present stochastic model are first recalled. Then, results obtained with the standard form of the model are presented along with an analysis which has been carried out to check the sensitivity of the predictions on different mean fluid quantities. These results show that the physical repre- sentation of the near-wall physics has to be improved and that, in particular, one possible route is to introduce specific features related to the near-wall coherent structures. In the following, we propose a simple phenomenological model that introduces some of the effects due to the presence of turbulent coherent structures on particles in a thin layer close to the wall. The results obtained with this phenomenological model are in good agreement with experimental evidence and this suggests to pursue in that direction, towards the development of more general and rigorous stochastic models that provide a link between a geometrical description of turbulent flow and a statistical one.
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