Turbulent Particle-Fluid Flows

1335965圆周率：繁荣虽然已经对湍流中悬浮点状颗粒的影响进行了大量的数值研究，但只有非常有限的信息可用于颗粒尺寸与流动的长度尺度相当或超过流动长度尺度的情况，从柯尔莫戈洛夫长度开始。要克服的障碍是在颗粒所代表的复杂的、随时间演变的无滑移边界存在的情况下，解决详细的流动特征所需的主要计算工作量。PI开发了一种强大的计算方法来解决这一困难，最近通过为基于GPU的计算机重新编程使其变得更加高效。这种方法将被用来对具有数千个悬浮有限尺寸颗粒的湍流流动进行真正直接的数值模拟，并从数值结果中提取由颗粒引起的流体湍流修正的各种特征的信息。除了这些关于弥散颗粒流的具体结果外，这项工作的目标之一是演示在基于GPU的工作站上运行常规模拟的可能性，该模拟涉及体积分数在0.05到0.20之间的数千个颗粒。自然过程提供了大量固体颗粒通过流体流动的实例：海洋沉积物、重力流、沙丘和许多其他。这种流动也具有很大的技术相关性，主要是在能源领域，其中沸腾床燃烧器、催化石油裂化、煤气化炉和化学环路燃烧器是主要例子。对这些系统的可靠理论理解是至关重要的，因为各种原因，从环境流动的建模到碳封存，到开发新的或扩大的设计而不需要昂贵的初步实验，以及许多其他原因，本项目将进行的数值模拟将提供这些系统。

1335965 PI: ProsperettiWhile much numerical research has been conducted on the effect of suspended point-like particles in a turbulent flow, only a very limited amount of information is available for situations in which the particle size is comparable to, or exceeds, the length scales of the flow, from the Kolmogorov length on up. The obstacle to overcome is the major computational effort necessary to resolve the detailed flow features in the presence of the complex, time-evolving no-slip boundaries represented by the particles. The PI has developed a powerful computational method to address this difficulty, which has recently been made even more efficient by reprogramming it for GPU-based computers. This method will be used to run truly direct numerical simulations of turbulent fluid flows with thousands of suspended finite-size particles and to extract from the numerical results information on various features of the fluid turbulence modification caused by the particles. In addition to these specific results on disperse particulate flows, one of the aims of the work is to demonstrate the possibility of running routine simulation involving many thousands of particles at volume fractions between 0.05 and 0.20 on GPU-based work stations in a matter of hours or a few days at most.Natural processes offer a wealth of instances in which solid particles are transported by fluid flows: marine sediments, gravity currents, sand dunes and many others. Such flows are also of great technological relevance, primarily in the energy area where fluidized bed combustors, catalytic oil cracking, coal gasifiers ad chemical looping combustors are prime examples. A reliable theoretical understanding of these systems, which the numerical simulations to be undertaken in this project will provide, is essential for a variety of reasons ranging from the modeling of environmental flows to carbon sequestration, to the development of new or scaled-up designs without expensive preliminary experimentation, and many others.