Richard J.A.M. Stevens

Professor at the University of Twente

Wind energy · Turbulence · Environmental flows

Publication 115 · Thermal convection

How wide must Rayleigh–Bénard cells be to prevent finite aspect ratio effects in turbulent flow?

R.J.A.M. Stevens, R. Hartmann, R. Verzicco, D. Lohse, J. Fluid Mech. 1000, A58 (2024).

Read the article Open-access version

Main finding

The cell width needed to avoid sidewall effects depends on which flow quantity is measured. In the tested simulations, heat transport and several mean flow measures approach their wide-cell values at a diameter-to-height ratio of about four; variance and local flow organization require ratios up to 16. These results do not establish a universal width or a sufficient width for ultimate-regime convection.

Heat transport and three Reynolds numbers against cell width at two Rayleigh numbers
How to read the figure. (a) Nusselt number and (b-d) total, vertical and horizontal Reynolds numbers against aspect ratio, for cylindrical and periodic cells at two Rayleigh numbers. These integral quantities reach their wide-domain values by an aspect ratio of about four. Open the full-resolution figure. Figure 1. R.J.A.M. Stevens et al. (2024). No separate licence is stated here; consult the original publication and credited source before reuse.

Why this matters

A box can be wide enough for averages but not fluctuations.

Research context

The study connects earlier wide-periodic-domain evidence to cylindrical cells with sidewalls. Sidewalls locally inhibit thermal-superstructure formation, which explains why selected integral quantities converge near aspect ratio four while variance and local organization require widths up to about sixteen.

Related findings: Radial boundary layer structure and Nusselt number in Rayleigh-Bénard convection; Turbulent thermal superstructures in Rayleigh-Bénard convection.

View in the complete publication list Related thermal convection research