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Guinness beer, a dark brown beer, is pressurized with nitrogen. When pouring Guinness beer into a glass of beer, small diameter bubbles (only 1/10 of those contained in soft drinks such as soda and sparkling water) disperse throughout the glass and the glass. Texture movement of the swarm of bubbles is moving down.
Although some models have been proposed to explain the downward movement of a swarm of bubbles during wave formation in Guinness beer, the mechanism underlying texture formation was an open problem.
Because Guinness beer, opaque and dark in color, obstructs physical observation in a glass and that the use of supercomputers requires voluminous computations for numerical flow simulation including a large number of small bubbles in the Beer, the team of researchers led by Tomoaki Watamura has "fluid pseudo-Guinness" using light particles and tap water. They filmed the movement of the liquid with a high-speed video camera applying the laser-induced fluorescence method to accurately measure the movement of the fluid. In addition, using molecular tags, they visualized the irregular movement of the fluid.
With these methods, the team poured pseudo-Guinness fluid into an inclined container to observe the evolution of the texture. The texture formation only appeared in the region of about 1 mm from the inclined wall and did not appear near the vertical wall.
They also observed a clear fluid film (without bubble) flowing along the inclined wall in the vicinity of the inclined wall, capturing the velocity and thickness of the bubble-free film flowing downward. Although the texture appeared when the tilt angles of the glass were low, it was not when it was large, demonstrating that the formation of texture in a glass of Guinness beer was due to the instability of the rolling waves of the gravity current.
Lead author Watamura said, "There are a large number of small objects in nature, such as fine particles of rock carried from rivers to the sea and micro-organisms living in lakes and ponds. the movement of small objects is important in various industrial processes Our research results will be useful for understanding and controlling the flow of bubbles and particles used in industrial processes, as well as protein crystallization and cell culture used in the sciences of life. "
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Material provided by University of Osaka. Note: Content can be changed for style and length.
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