Hysteretic transitions between Rayleigh–Bénard and horizontal convection in an experimental model of subglacial lakes
Year: 2026
Type: article
Abstract: We investigate experimentally the flow structure in a fluid layer of thermal conductivity $k$ , heated from below with a uniform heat flux $F$ , and exposed to a horizontal temperature gradient, $\lambda$ , on the top plate. This is a model system for the dynamics in subglacial lakes where such a competition between Rayleigh–Bénard convection (RBC) and horizontal convection (HC) is thought to happen. We evidence a hysteretic transition from a RBC flow structure to a HC flow structure when the non-dimensional control parameter, $\varLambda = k\lambda /F$ , is $4\times 10^{-4}$ when $\varLambda$ is decreasing, and $7\times 10^{-4}$ when $\varLambda$ is increasing. These values are lower than the threshold value found in recent two-dimensional direct numerical simulations (Couston et al. 2022 J. Fluid Mech. , vol. 947, p. A13), of order $10^{-2}$ , highlighting the importance of exploring three-dimensional dynamics at higher realistic Prandtl numbers, and suggesting that HC may be more common in subglacial lakes than previously predicted. For large values of $\varLambda$ , we observe that the warmest part of the top plate has approximately the same temperature as the bottom plate, such that a stable temperature gradient settles below the warm side of the top plate. Thermal plumes are no longer visible in this region, and seem to be replaced by internal gravity waves.
Source: Journal of Fluid Mechanics
Language: English
Subfield: Computational Mechanics
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,550
OpenAlex ID: W7155190740