This submission showcases the fascinating dynamics of double-diffusive instability (DDI) through a series of experiments capturing the intricate interplay between thermal and solutal gradients. The experiments were conducted using Planar Laser-Induced Fluorescence (PLIF) imaging technique, allowing for precise and quantitative measurements. The video highlights the early and late stages of DDI, where cold, fresh water is injected through a perforated tube at the bottom of a tank filled with hot, salty water. The experiment reveals the growth and evolution of characteristic ascending fingers, which emerge as slender, upward-moving plumes. These fingers eventually transition into more complex, mushroom-shaped structures before merging and mixing into the surrounding fluid. Early-stage development emphasizes the initial formation of these fingers, where small perturbations in the fluid lead to the onset of instability. The fingers exhibit a rhythmic, dancing motion as they rise, driven by the differential diffusion of heat and salt. This stage is critical for understanding how small-scale instabilities grow and evolve under varying density and temperature gradients. In the late-stage development, the video captures the dramatic transformation of the fingers as they begin to interact more intensely. The fingers stretch, twist, and merge, forming mushroom-shaped structures that dominate the visual field. This stage provides valuable insights into the nonlinear interactions and the eventual transition to a more mixed, turbulent state.
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