Lattice-Boltzmann simulation of heat transfer in turbulent pipe flows seeded with resolvednon-spherical particles

承载颗粒的湍流在广泛的工业和自然过程中无处不在，包括生物质燃烧、污染物运输、沙尘暴、冰云等。在大多数这些应用中，粒子的形状不是球形的。非球形颗粒湍流的数值模拟是复杂的，因为颗粒的取向和分布对流动和湍流行为有着重要的影响。大多数涉及非球形颗粒的湍流的数值研究都局限于点颗粒。然而，当粒子大于柯尔莫哥洛夫长度尺度时，模拟就会变得更加复杂，需要大量的计算工作。迄今为止，科学文献中对非球形颗粒界面分解湍流的数值研究很少。这些研究大多考虑了等温条件。然而，热从/到颗粒的传递可以再次显著改变所有流动特性。热粒子也可以通过压力膨胀来改变湍流谱。这种影响在过去从未得到彻底解决。本研究的目标是通过对包含非球形颗粒的湍流进行直接数值模拟（DNS）并考虑传热效应来弥补这一差距。考虑到问题的复杂性和模拟所需的高计算成本，本研究选择晶格玻尔兹曼方法（LBM）求解器。由于所有操作的局部性，使用LBM进行并行计算非常简单。此外，它可以相对容易地应用于复杂的领域，这使得它适合于本提案的目的。为此，将采用浸入边界法与LBM求解器相结合的方法。为了提供与实际应用相关的信息，最后的模拟将考虑管道流动，为更好地物理理解催化反应器中的颗粒位置或热交换器中的污垢等重要现象打开大门。这样的DNS（这里基于LBM）将提高我们对物理传输机制的理解。结合湍流，非等温和流体动力学方面，并考虑在非球形粒子运动过程中发生的相互作用是本建议的中心目标。这项研究的结果也将使有关传热增强的实际进展，可能与减阻效果相结合。

Turbulent flows laden with particles are ubiquitous in a wide range of industrial and natural processes including biomass combustion, pollutant transport, sand storms, icy clouds, etc. In most of these applications particle shape is not spherical. Numerical simulation of turbulent flows with non-spherical particles is complicated because the orientation and distribution of particles play an important role and can significantly modify flow and turbulence behavior. Most numerical studies dealing with turbulent flows involving non-spherical particles are limited to point particles. However, when particles become larger than the Kolmogorov length scale, simulations become more complex and demand large computational efforts. Very few numerical studies of turbulent flows with interface-resolved non-spherical particles can be found in the scientific literature up to now. Most of these studies have considered isothermal conditions. However, heat transfer from/to particles can again significantly alter all flow properties. Hot particles can also modify the turbulence spectra through pressure dilatation. Such effects have never been addressed thoroughly in the past. The goal of this study is to bridge this gap by performing direct numerical simulation (DNS) of turbulent flows containing non-spherical particles and considering heat transfer effects. Given the complexity of the problem and very high computational costs required for the simulations, a lattice Boltzmann method (LBM) solver is chosen for this study. Due to the locality of all operations, parallel computations are straightforward with LBM. Moreover, it can relatively easily be applied to complex domains, which makes it suitable for the purpose of the present proposal. To this end, an immersed boundary method (IBM) combined with an LBM solver will be employed. In order to deliver information relevant for practical applications, the final simulations will consider a pipe flow, opening the door for a better physical understanding of important phenomena like particle position in catalytic reactors, or fouling in heat exchangers. Such DNS (here based on LBM) will improve our understanding of the physical transfer mechanisms. Combining turbulence, non-isothermal and fluid dynamics aspects and considering the mutual interactions that occur during the motion of non-spherical particles are the central goals of this proposal. The results of this study will also enable practical progress concerning heat transfer enhancement, possibly coupled to drag-reduction effects.