Venturi Luminous CurrentsQingyang HeAward: Top 100
School: the experimental high school attached to beijing normal university This photograph captures a beam from my phone's flashlight traversing a Venturi tube in a darkened chamber, revealing vivid refractive caustics along its hourglass profile. I self-designed and hand-crafted this tube to develop and optimize a dust remover that leverages the Coanda effect in fluid mechanics. Precision-machined from clear PMMA (refractive index ˜1.49), the tube ensures excellent optical clarity with minimal scattering. As light enters the curved walls, it bends toward the normal at the air–acrylic interface and then away from the normal when exiting into the fluid, following the principles of geometric refraction. The converging and diverging sections act as opposing lenses, concentrating incident rays into bright envelopes--known as caustics--where the curvature is steepest. These envelopes trace the surface-slope gradients of the Venturi geometry, with the narrow throat producing the sharpest, petal-shaped patterns. Discovered unexpectedly during my dust-removal experiments--driven by the Venturi-induced pressure drop--these caustics vividly illustrate the interplay between fluid mechanics and geometric optics. Although the pressure reduction at the throat, which is central to particle entrainment in my design, does not directly affect the light, it highlights how flow-driven shapes can be visualized through refraction. By aerodynamically sculpting the Venturi profile, I reveal otherwise invisible currents as a luminous tapestry. I was struck by the poetic harmony of physics, where unseen flows become glowing ribbons dancing along the tube's curves. 
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