Converging material with two bulges

In numerical studies of thermal convection that includes a layer of lighter surface fluid, the light fluid naturally forms clusters that bulge downward at downwelling sites. A curious result is that in some cases, the clusters have maximum bulging downward near the sides of the cluster instead of a...

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Bibliographic Details
Published in:Journal of fluid mechanics 2024-02, Vol.980, Article A26
Main Author: Whitehead, J.A.
Format: Article
Language:English
Subjects:
Bulging
Cellular convection
Clusters
Convection
Convection cells
Corn syrup
Divergence
Downwelling
Fluid dynamics
Fluid flow
Fluid mechanics
Free convection
JFM Papers
Kinematics
Rayleigh number
Scaling
Simulation
Vertical motion
Vorticity
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Summary:In numerical studies of thermal convection that includes a layer of lighter surface fluid, the light fluid naturally forms clusters that bulge downward at downwelling sites. A curious result is that in some cases, the clusters have maximum bulging downward near the sides of the cluster instead of a single bulge downward centred above the downwelling. The fluid mechanics leading to this ‘double bulge’ formation is analysed. To accomplish this, a simplified model replaces the thermally driven convection cells with driving cells with a fixed speed. Adding a layer of dense fluid on the bottom to the previous configuration leads to bulges along the top and bottom. More importantly, this allows a new scaling that reduces the number of governing parameters from four to three and even to two in this study. The mechanism for the double bulges comes from buoyancy of the clusters. This produces localized vorticity at the sides of the cluster that has the opposite sign of the driving cells. When this vorticity is approximately the same order of magnitude as the driving cell vorticity, a divergence in the middle of each cluster leads to the double bulges. The effect can be so great that the underlying flow cells are tilted so that vertical motion is reversed under the middle of each bulge.
ISSN:0022-1120
1469-7645
DOI:10.1017/jfm.2024.10