Confined inclined thermal convection in low-Prandtl-number fluids

Any tilt of a Rayleigh–Bénard convection cell against gravity changes the global flow structure inside the cell, which leads to a change of the heat and momentum transport. Especially sensitive to the inclination angle is the heat transport in low-Prandtl-number fluids and confined geometries. The purpose of the present work is to investigate the global flow structure and its influence on the global heat transport in inclined convection in a cylindrical container of diameter-to-height aspect ratio Γ = 1/5. The study is based on direct numerical simulations where two different Prandtl numbers Pr = 0.1 and 1.0 are considered, while the Rayleigh number, Ra, ranges from 106 to 109. For each combination of Ra and Pr, the inclination angle is varied between 0 and π/2. An optimal inclination angle of the convection cell, which provides the maximal global heat transport, is determined. For inclined convection we observe the formation of two system-sized plume columns, a hot and a cold one, that impinge on the opposite boundary layers. These are related to a strong increase in the heat transport