Heat exchange improvement and drag force reduction around a heated square cylinder controlled by three partitions

Abstract

This paper presents a detailed numerical study of airflow and heat transfer around a heated square obstacle controlled by three partitions in a horizontal channel at a fixed Reynolds number (\(\text{Re} = 150\)). The numerical approach employed is the lattice Boltzmann method (LBM). The primary objective is to examine the influence of key geometric parameters, namely the gap spacing g between the cylinder and the partitions, and the partition’s length \(Lp\), on both drag reduction and heat exchange enhancement. The results highlight that when the partitions are positioned upstream of the obstacle, a significant reduction in the drag coefficient is achieved due to the disruption of the approaching boundary layer, which weakens the vortex shedding behind the cylinder. The peak drag reduction of \(66.10\%\) is observed at \(g=1.5d\), as the partitions effectively mitigate the adverse pressure gradient in the wake region. Further increasing the partition length to \(Lp=2.5d\) enhances this effect, leading to a maximum drag reduction of \(72.68\%\). This configuration also promotes better thermal mixing, resulting in a uniform and consistent heat transfer enhancement across the obstacle’s surfaces. In contrast, when the partitions are placed downstream of the obstacle, the reduction in drag is less pronounced, reaching a maximum of \(31.45\%\) at \(g=2.5d\). This is because the vortex shedding remains active, albeit with reduced intensity. However, this setup significantly enhances convective heat transfer, increasing the Nusselt number by \(14\%\) compared to the case without partitions. The downstream partitions serve as flow stabilizers, promoting heat advection away from the heated surfaces and reducing thermal recirculation zones. The most efficient configuration combines both upstream and downstream partitions, leading to an optimal aerodynamic and thermal performance. In this case, the upstream partitions effectively weaken the vortex shedding, while the downstream partitions act as additional flow stabilizers, further reducing pressure drag. This synergistic effect results in a maximal drag reduction of \(78.31\%\), coupled with a \(15.35\%\) improvement in the Nusselt number. The presence of both partitions ensures a more uniform temperature distribution and enhances convective heat dissipation, demonstrating the effectiveness of flow control strategies in optimizing both aerodynamic and thermal characteristics.