Richard J.A.M. Stevens

Physics of Fluids · University of Twente

Publication 12 · Thermal convection

Effect of plumes on measuring the large scale circulation in turbulent Rayleigh-Bénard convection

R.J.A.M. Stevens, H.J.H. Clercx, D. Lohse, Phys. Fluids, 23, 095110 (2011).

Main finding

The relative LSC strength compares first-mode energy with all resolvable azimuthal Fourier modes. At Ra=10^8 it is substantially lower in Γ=1/2 than in Γ=1. A cosine-like conditional average can appear even when instantaneous relative LSC strength is low; orientation averaging therefore does not prove a dominant SRS.

Probability distributions of relative large-scale circulation strength for two aspect ratios
How to read the figure. Probability distributions of the relative strength of the large-scale circulation at mid-height - the energy in the first azimuthal Fourier mode against all resolvable modes - at Ra = 10^8. The distribution sits substantially lower in the slender cell than in the unit-aspect-ratio cell. Figure 14 shows that averaging over orientation still produces a cosine-like profile even when the instantaneous strength is low, so that profile does not by itself prove a dominant single-roll structure. Open the full-resolution figure. Figure 15. R.J.A.M. Stevens et al. (2011). No separate licence is stated here; consult the original publication and credited source before reuse.

Why this matters

The relative LSC strength compares first-mode energy with all resolvable azimuthal Fourier modes. At Ra=10^8 it is substantially lower in Γ=1/2 than in Γ=1.

Research context

Full-field simulations show how sparse azimuthal temperature probes can alias plume and corner-flow structure into the first Fourier mode. The result connects flow-state studies to measurement practice and explains why an orientation-averaged cosine profile is not sufficient evidence for a dominant single-roll state.

Read the article View in the complete publication list Related thermal convection research