Ouzo in Greece, pastis in France, and sambuca in Italy, are anise-flavored alcohol drinks. The so-called ouzo effect occurs when pouring water into a mixture solution of ethanol, anise oil, and water. Among the three components, ethanol is miscible with both water and oil; however, water and oil are immiscible. When mixing with an excessive amount of water, oil can no longer stay dissolved, and thus nucleates out of the solution. The nucleated oil droplets will scatter light, exhibiting a milky appearance.
As the ouzo effect originates from the mixing, we dive into the playground of the mixing process - turbulence. Turbulent flow is known for its multiscale nature, from small-scale diffusion to large-scale enhanced transport. The nucleation of micro-sized droplets further enriches the process with the light-scattering feature. Utilizing the flow properties and the geometric constraints, we demonstrate the versatility of the ouzo effect in turbulent flows, scientifically and aesthetically.
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