Abstract

This work consists of a numerical evaluation of the geometry of an arrangement of square heated obstacles under mixed convective turbulent flows. The geometry is evaluated using the Constructal Design method. The geometry has two degrees of freedom: the longitudinal distance ratio between the frontal bluff body and the posterior ones and the ratio of the transversal distance between the posterior bluff bodies. The flow is also evaluated for three Richardson number values. In all simulations, Reynolds and Prandtl numbers are considered equal to \(Re_{D}= 22,000\) and \(Pr= 0.71\), respectively. The problem is modeled through the classical turbulence modeling with the SST—\(\kappa\)-\(\omega\) closure model. The main objective of the study is to evaluate how the variation in geometry of the arrangement of bluff bodies and different conditions of mixed convection influences the mean drag coefficient and Nusselt number on the arrangement. The variation of mixed convection conditions led to different effects of longitudinal and transversal pitches over the performance indicators, demonstrating that the mechanism of mixed convection strongly influences the arrangement design. For Ri = 1.0, the solutions for the drag coefficient and Nusselt number curves are smoothed due to the natural convection being in the auxiliary flow direction, which thins the boundary layers. The opposite is noticed for \(Ri= -1.0\), where the opposing forces between natural and forced convection intensified the free shear flow, increasing the thickness of turbulent boundary layers.

中文翻译：

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混合对流换热湍流下钝体排列的几何评估

摘要

这项工作包括对混合对流湍流下方形加热障碍物排列的几何形状进行数值评估。使用结构设计方法评估几何形状。几何形状有两个自由度：前钝体与后钝体之间的纵向距离比和后钝体之间的横向距离比。还针对三个理查森数值评估流量。在所有模拟中，雷诺数和普朗特数被认为分别等于 \(Re_{D}= 22,000\) 和\(Pr= 0.71\)。该问题通过 SST 的经典湍流建模进行建模- \(\kappa\) - \(\omega\) 闭合模型。该研究的主要目的是评估钝体排列的几何变化和混合对流的不同条件如何影响排列的平均阻力系数和努塞尔数。混合对流条件的变化导致纵向和横向节距对性能指标的影响不同，表明混合对流的机制强烈影响布置设计。当Ri  = 1.0 时，由于辅助流动方向上的自然对流使边界层变薄，阻力系数和努塞尔数曲线的解被平滑。对于\(Ri= -1.0\)则相反 ，其中自然对流和强制对流之间的相反力增强了自由剪切流，增加了湍流边界层的厚度。