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 approximate to 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 x 10(3) <= Ra-H <= 10(8) (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.