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Abstract

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.