The objective of this research is to study the fluid flow control allowing the reduction of aerodynamic drag around a square cylinder using two parallel partitions placed downstream of the cylinder using the lattice Boltzmann method with multiple relaxation times (MRT-LBM). In contrast to several existing investigations in the literature that study either the effect of position or the effect of length of a single horizontal or vertical plate, this work presents a numerical study on the effect of Reynolds number (Re), horizontal position (g), vertical position (a), and length (Lp) of the two control partitions. Therefore, this work will be considered as an assembly of several results presented in a single work. Indeed, the Reynolds numbers are selected from 20 to 300, the gap spacing (0 ≤ g ≤ 13), the vertical positions (0 ≤ a ≤ 0.8d), and the lengths of partitions (1d ≤ Lp ≤ 5d). To identify the different changes appearing in the flow and forces, we have conducted in this study a detailed analysis of velocity contours, lift and drag coefficients, and the root-mean-square value of the lift coefficient. The obtained results revealed three different flow regimes as the gap spacing was varied. Namely, the extended body regime for 0 ≤ g ≤ 3.9, the attachment flow regime for 4 ≤ g ≤ 5.5, and the completely developed flow regime for 6 ≤ g ≤ 13. A maximal percentage reduction in drag coefficient equal to 12.5%, is given at the critical gap spacing (gcr = 3.9). Also, at the length of the critical partition (Lpcr = 3d), a Cd reduction percentage of 12.95% was found in comparison with the case without control. Moreover, the position of the optimal partition was found to be equal to 0.8d i.e. one is placed on the top edge of the square cylinder and the second one is placed on the bottom edge. The maximum value of the lift coefficient is reached for a plate length Lp = 2d when the plates are placed at a distance g = 4. On the other hand, this coefficient has almost the same mean value for all spacings between the two plates. Similarly, the root means the square value of the lift coefficient (Clrms) admits zero values for low Reynolds numbers and then increases slightly until it reaches its maximum for Re = 300.

The present study evaluates the heat transfer performance of an immersion liquid cooling system, utilizing copper-water (Cu-water) nanofluids under various flow and geometric conditions, including different Reynolds and Rayleigh numbers, nanoparticle volume fractions, and block spacing configurations. To this end, numerical simulations were conducted to assess the impact of these parameters on the system’s temperature distribution and overall cooling efficiency. The findings indicate that augmenting the Reynolds number from 100 to 500, and the nanoparticle volume fraction from 0% to 5%, at a Rayleigh number of 10⁵, results in substantial enhancements in heat transfer, with improvements reaching up to 193.8%. Furthermore, an increase in the Rayleigh number from 10³ to 10⁶, in conjunction with elevated nanoparticle concentrations at a Reynolds number of 500, yielded a heat transfer enhancement of up to 36.3%. These findings demonstrate that higher Reynolds and Rayleigh numbers promote better heat dissipation through increased convective flow and buoyancy-driven convection. Furthermore, the study underscores the pivotal function of block spacing in maximizing cooling efficacy. While closer spacing results in higher temperatures, wider spacing improves heat transfer efficiency by reducing thermal interference between blocks. The study emphasizes the synergistic effect of an enhanced thermal conductivity, strong convective flow, and optimal geometric configurations in maximizing cooling efficiency. These findings are of crucial importance for the design of more efficient thermal management systems, with applications in electronics cooling, energy systems, and industrial processes.

Investigating the subject offers a pioneering approach to enhancing thermal performance and aerodynamic efficiency, unlocking novel strategies for optimizing energy utilization and air dynamics in engineering applications. In this research, a numerical study of airflow control coupled to heat transfer around several heated square cylinders is carried out at a fixed Reynolds number (Re=100). The effect of the positioning and length of the control partitions is examined. Numerical simulations are carried out using the lattice Boltzmann method with multiple relaxation times model. The obtained results reveal the existence of a critical position g=0 where a significant improvement in the Nusselt number is observed. This improvement amounts to 31.1% for the rear face of the top obstacle, 30.2% for the rear face of the central obstacle, and 36.65% for the rear face of the bottom obstacle compared to the uncontrolled case. Thus, a complete suppression of the vortex shedding is observed when the length of the partitions reaches a critical value (Lp=4D). Furthermore, a maximum percentage of drag reduction is achieved by around 6.03% for the central block and 16.67% for the two end blocks when the length of the control partitions reaches this critical value.