从多孔介质湍流直接数值模拟中我们能学到什么：复合多孔/流体域中湍流流动的建模
What We Can Learn From DNS of Turbulence in Porous Media: Modeling Turbulent Flow in Composite Porous/Fluid Domains
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- North Carolina State University（北卡罗来纳州立大学）
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中文总结 AI 辅助
基于多孔介质DNS发现湍流尺度受孔隙限制，提出复合多孔/流体域湍流模型，强调界面粗糙度对换热影响大于多孔区湍流。
中文摘要 AI 辅助
我们最近发表的关于多孔介质中强迫对流流动直接数值模拟（DNS）结果的论文表明，在多孔介质中，湍流结构的尺寸受孔隙尺度的限制。由于湍动能主要包含在大涡中，这表明多孔介质中的湍流流动可能比其在清晰流体域中的对应流动携带更少的能量。我们利用这一见解开发了一种实用的复合多孔/流体域中湍流流动模型。在此类域中，大部分流动预计发生在清晰流体区域；因此，在大多数情况下，即使清晰流体区域中的流动完全湍流，多孔区域中的流动要么保持层流，要么开始向湍流过渡。这一结论通过将相应的雷诺数与它们的临界值进行比较得到证实。因此，对于大多数情况，在动量方程中使用Forchheimer项和在能量方程中使用热扩散项可能足以对多孔区域进行良好建模。然而，真正可能影响复合域中湍流对流的可能是多孔/流体界面的粗糙度。如果构成多孔介质（和孔隙）的颗粒或纤维相对较大，则粗糙度对复合多孔/流体域中对流换热的影响可能比多孔区域中可能的湍流的影响重要得多。我们利用上述考虑开发了一种实用的复合多孔/流体域中湍流流动模型，重点关注界面粗糙度对湍流的影响。
英文摘要
Our recently published papers reporting results of Direct Numerical Simulation (DNS) of forced convection flows in porous media suggest that in a porous medium the size of turbulent structures is restricted by the pore scale. Since the turbulent kinetic energy is predominantly contained within large eddies, this suggests that turbulent flow in a porous medium may carry less energy that its counterpart in a clear fluid domain. We use this insight to develop a practical model of turbulent flow in composite porous/fluid domains. In such domains, most of the flow is expected to occur in the clear fluid region; therefore, in most cases the flow in the porous region either remains laminar or starts its transition to turbulence even if the flow in the clear fluid region is fully turbulent. This conclusion is confirmed by comparing appropriate Reynolds numbers with their critical values. Therefore, for most cases, using the Forchheimer term in the momentum equation and the thermal dispersion term in the energy equation may result in a sufficiently good model for the porous region. However, what may really affect turbulent convection in composite domains is the roughness of the porous/fluid interface. If particles or fibers that constitute the porous medium (and the pores) are relatively large, the impact of the roughness on convection heat transfer in composite porous/fluid domains may be much more significant than the impact of possible turbulence in the porous region. We use the above considerations to develop a practical model of turbulent flow in a composite porous/fluid domain, concentrating on the effect of interface roughness on turbulence.
