Thermal Buoyancy as a Wake Controller: Coupled Wake Dynamics and Heat Transfer in Mixed Convection

Abstract

The dominance and impact of pronounced thermal buoyancy effects on the thermal and hydrodynamic properties of a horizontally heated cylinder of circular configuration immersed in a vertically ascending laminar flow stream have been numerically investigated. The dynamics are determined by numerically solving the standard energy and two-dimensional laminar Navier–Stokes equations and by incorporating buoyancy through the Boussinesq approximation in the mixed-convection co-flow configuration. The Reynolds number (Re) is varied within the range of 80≤Re≤160, while the Prandtl number (Pr) is maintained constant at 0.71. The thermal buoyancy effect of the co-flow configuration is assessed by altering the Richardson number (0≤Ri≤1). The code is validated against and compared against several numerical and experimental results, and its strong prediction capabilities are confirmed. This study examines significantly observed von Kármán vortices and their disappearance at above a threshold Richardson number, which has been identified as the critical Richardson number. This study provides a detailed explanation of a new phenomenon, termed ‘vortex switching’, which arises from the interaction between inertia–buoyancy interactions. The study showcases representative patterns of vorticity, streamlines, and isotherms while also plotting the average Nusselt numbers against the Ri for various Re. Furthermore, it offers a correlation for the changes in wake width, recirculation bubble length, and vortex switching length, which are essential for optimizing design and enhancing thermal efficiency. Lastly, the thermal characteristics provide deeper insights into the impact of thermal buoyancy on wake dynamics and heat transfer.