Why do bubbles in Guinness sink?
(Color online) Numerical simulations of bubbly flows for the pint and anti-pint. The curves show the streamlines for the bubbles, the shading (color) shows the void fraction f. The snapshots displayed correspond to . Observe the region of reduced f near the wall of the pint; the corresponding near-wall region of increased f in the anti-pint is not visible in this figure but can be observed in Fig. 2 .
The half-height ( ) cross-sections of the vertical velocity u and the void fraction f for the pint and anti-pint geometries (these graphs correspond to the (r, z) diagrams shown in Fig. 1 ). The dotted lines in the upper panels separate the regions of upward/downward flow.
The global void fraction f (i.e., the proportion of gas in the container) versus time t, for the three cases: the pint (p) and anti-pint (a), both illustrated in Fig. 2 , and a cylinder of the same volume (c).
Schematic diagram of the evolution of bubbles near the wall for: (a) container narrowing downwards (the bubbles move away from the wall), and (b) container widening downwards (the bubbles move towards the wall, and eventually accumulate there) (enhanced online). [URL: http://dx.doi.org/10.1119/1.4769377.1]doi: 10.1119/1.4769377.1.
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