Unveiling the dynamics of inclined thermal convection

We have numerically unraveled the mechanism of thermal convection in inclined circular enclosures. The study delves into how inclination angles between thermal gradients and gravity influence heat transport, offering new insights into processes that shape geophysical landscapes and planetary climates. From an engineering perspective, this research holds significant promise for optimizing the inclination angle of thermosiphons, solar collectors, and heat exchangers to enhance heat transport. Through numerical simulations, we explored thermal convection in a circular disc where the thermal gradient is inclined to gravity. When the thermal gradient aligns with gravity, flow features consist of large-scale circulation with occasional flow reversal. As the inclination angle increases, the flow complexity escalates, producing dipole and tripole modes and ultimately evolving into a multi-roll state. Our scaling analysis shows dimensionless heat transport is proportional to (Ra cosΦ)^1/3 at small Φ (0 ≤ Φ< π/9) and to (Ra sinΦ)^1/4 at large Φ (π/9 ≤ Φ ≤ π/2), where Ra is the Rayleigh number and Φ is the inclination angle. In contrast, the Reynolds number based on the global root mean square velocity shows a continuous decrease with Φ due to the reduction in buoyancy fluxes, which convert the available potential energy into kinetic energy. Despite reduced kinetic energy, these flows exhibit efficient heat transport, as indicated by a high Nusselt number due to irreversible mixing.