Geometric Evaluation of Bluff Bodies Arrangement under Turbulent Flows with Mixed Convection Heat Transfer

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.