Turbulent Particle-Fluid Flows

1335965 PI：Prosperetti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，但对于颗粒尺寸与流动的长度尺度相当或超过流动的长度尺度（从Kolmogorov长度开始）的情况，只有非常有限的信息可用。要克服的障碍是主要的计算工作所需的解决的复杂的，随时间变化的无滑移边界所代表的粒子的存在下的详细的流动特征。PI开发了一种强大的计算方法来解决这个难题，最近通过为基于GPU的计算机重新编程，使其变得更加高效。这种方法将被用来运行真正的直接数值模拟的湍流流体流动与数以千计的悬浮有限尺寸的颗粒，并从数值结果中提取的各种功能的流体湍流修改所造成的颗粒的信息。除了这些关于分散颗粒流的具体结果之外，这项工作的目的之一是证明在几个小时或最多几天内在基于GPU的工作站上运行涉及体积分数在0.05和0.20之间的数千个颗粒的常规模拟的可能性。自然过程提供了大量固体颗粒通过流体流动传输的实例：海洋沉积物、重力流、沙丘和许多其他物质。这种流动也具有很大的技术相关性，主要是在能源领域，其中流化床燃烧器、催化油裂化、煤气化器和化学链燃烧器是主要的例子。这些系统的可靠的理论理解，在这个项目中进行的数值模拟将提供，是必不可少的各种原因，从建模的环境流动到碳封存，新的或按比例放大的设计，而无需昂贵的初步实验，和许多其他的发展。

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.