Dynamics and length scales in vertical convection of liquid metals

Using complementary experiments and direct numerical simulations, we study turbulent thermal convection of a liquid metal (Prandtl number Pr 0. 03) in a box-shaped container, where two opposite square sidewalls are heated/cooled. The global response characteristics like the Nusselt number {Nu} and the Reynolds number Re collapse if the side height L is used as the length scale rather than the distance H between heated and cooled vertical plates. These results are obtained for various Rayleigh numbers 5 10³ {Ra}H 10⁸ (based on H) and the aspect ratios L/H=1, 2, 3 and 5. Furthermore, we present a novel method to extract the wind-based Reynolds number, which works particularly well with the experimental Doppler-velocimetry measurements along vertical lines, regardless of their horizontal positions. The extraction method is based on the two-dimensional autocorrelation of the time–space data of the vertical velocity.