一种模拟热力作用下流体绕过和通过多孔介质钝体流动的浸没边界法

The problems on flow past porous bluff body are attractive due to its strong academic value as well as its wide industry background. However, the understanding on this type of problems is still far from complete because of the coupling issue at the porous-fluid interface and thus further investigations are needed. The present project concerns the heat and fluid flow problems involved the porous-fluid interface. A novel algorithm, by introducing the concept of the immersed boundary method (IBM), will be developed to simulate the heat and fluid flow problems involved the porous-fluid interface with complex geometry. The advantages of the present algorithm include: 1) easy to generate mesh, 2) easy to discretise the governing equations, and 3) easy to develop codes. Moreover, this novel algorithm will be applied to investigate the unsteady flow past and through a porous circular cylinder under a wide range of parameters. The flow characteristics and underlying mechanisms, especially the transition process from steady state to unsteady state, will be explored and discussed further. The results would help to advance the understanding on this type of flow problems. The present algorithm will also be applied to study flow past and through a porous circular cylinder under thermal forcing. The flow and heat transfer behaviours will be summarized by varying important dimensionless parameters. The underlying physics behind the interaction between fluid flow and heat transfer will be explored and discussed further, which would provide useful guidance on the future numerical studies on the related problems.

多孔介质钝体绕流问题的研究不仅有很强的学术价值，还有广泛的工业应用背景。但由于涉及到界面的耦合问题，学术界对这些问题的研究还不是很透彻，需要进一步的探讨。本项申请围绕多孔介质和纯流体耦合流动和传热问题展开，重点包括引入浸没边界法的思想，发展一套新颖的算法，来模拟带有复杂几何形状的多孔介质和纯流体界面的流动和传热问题，同时还能保持网格生成简单、控制方程离散容易以及编程简洁等特性。本项申请将利用新算法来研究不同参数下非稳态多孔介质圆柱绕流问题的流动特性和机理，流动由稳态向非稳态转捩的过程及机理，加深学术界对这方面问题的理解。本项申请还将利用新算法来研究不同参数下有热力作用的多孔介质圆柱绕流问题，得到流动和传热的特性，揭示流动和传热相互作用的机理，为以后的相关模拟研究提供有价值的参考。

多孔介质钝体绕流广泛存在于自然界和工业应用中，但由于该类物理现象涉及到界面的耦合问题，学术界对这些问题的研究还不是很透彻，需要进一步的探讨。本项目围绕多孔介质和纯流体耦合流动和传热问题展开，基于浸没边界法的思想，已发展了一套能够准确模拟带有复杂几何形状的多孔介质和纯流体界面的流动和传热问题的新颖算法。另外，在该项基金的实施过程中，已分析了多孔介质钝体绕流的增阻/减阻机制以及尾涡的发生和消失机理；研究了孔隙尺度和宏观尺度多孔介质钝体绕流特征之间的联系并给出了新的阻力计算公式；观察了流动在稳态和非稳态之间的转捩行为，获得了流动演化的临界无量纲参数，阐明了全局涡街发生和抑制机理。对于有热力作用的多孔介质圆柱绕流问题，明确了重要无量纲数对流动和传热特性的影响，揭示了流动和传热相互作用的机理。本项基金的成果加深了学术界对多孔介质钝体绕流问题的理解，为以后的相关模拟研究提供有价值的参考。