Directional dependence of fluid flow on mixed convection across an isoflux cylinder with entropy generation

This article explores the impact of free-stream flow orientation on the dynamics of flow past a circular cylinder under superimposed thermal buoyancy subjected to isoflux condition. It emphasizes how thermal buoyancy regulates boundary layer separation across different flow angles, offering valuable insights for optimizing thermal management in mixed convection systems. The effect caused by the fluid flow and thermal dynamics is highlighted along with entropy generation around the cylinder for various Reynolds numbers ($5\le Re\le 40$), Richardson numbers ($0\le Ri\le 1.5$), and free-stream angles ($0^{\circ }\le \alpha \le 180^{\circ }$). A fourth-order accurate finite difference scheme with a stable pseudo-time iterative method is developed to address the non-linear governing continuity, momentum and energy equations. The key findings reveal that the flow configuration remains symmetric along aiding and opposing flow regimes; otherwise, it becomes completely asymmetric. The superimposed thermal buoyancy controls the wake formation, which is strongly dependent upon the thermal boundary condition and flow orientation. Critical Richardson number ($R{i}_{cr}$) for suppressing the vortex shedding is evaluated for various parameters, and inter-parametric dependence of the $R{i}_{cr}$ is also disclosed under isoflux boundary condition. The rate of heat transfer increases within aiding to cross flow regime, whereas the same decreases within cross to opposing flow regime. The relative contribution of heat transfer entropy to the overall entropy, characterized by Bejan number, reduces with increasing $Ri$ in aiding and cross flow regime, while it increases in opposing flow regime.